Pub Date : 2024-11-14DOI: 10.1016/j.matchar.2024.114547
Gangming Chen , Yongduo Sun , Hui Wang , Xuefei Huang
ZrC-dispersion strengthened FeCrAl (ZrC-FeCrAl) alloy is one of the promising cladding materials for advanced nuclear reactors. The thermal stability of ZrC-FeCrAl alloy is closely associated with its recrystallization behavior. In this study, the effects of different ZrC contents (0–1.5 wt%) on the recrystallization behavior of FeCrAl alloys were investigated. It was found that ZrC addition impedes the recovery and recrystallization processes, with higher ZrC content resulting in higher recrystallization temperatures. Specifically, the addition of 1.5 wt% ZrC increased the recrystallization finishing temperature from 700 °C to 1000 °C. ZrC delays the initiation and completion of recrystallization as well as the onset and termination of grain growth, with higher ZrC content leading to more pronounced delaying effects and extended incubation periods for recrystallization. Furthermore, ZrC influences recovery and recrystallization by affecting the precipitation of M23C6 and Al2O3. ZrC addition also significantly enhances both room-temperature (RT) and high-temperature strength of the alloys. While low ZrC content markedly improves ductility, excessive ZrC content can impair it. The FeCrAl alloy with 0.5 wt% ZrC exhibited the best comprehensive mechanical properties. Moreover, with increasing ZrC content, the fracture mode of the alloy shifts from ductile to brittle fracture.
{"title":"Effects of ZrC addition on the recrystallization behavior of ZrC-dispersion strengthened FeCrAl alloys","authors":"Gangming Chen , Yongduo Sun , Hui Wang , Xuefei Huang","doi":"10.1016/j.matchar.2024.114547","DOIUrl":"10.1016/j.matchar.2024.114547","url":null,"abstract":"<div><div>ZrC-dispersion strengthened FeCrAl (ZrC-FeCrAl) alloy is one of the promising cladding materials for advanced nuclear reactors. The thermal stability of ZrC-FeCrAl alloy is closely associated with its recrystallization behavior. In this study, the effects of different ZrC contents (0–1.5 wt%) on the recrystallization behavior of FeCrAl alloys were investigated. It was found that ZrC addition impedes the recovery and recrystallization processes, with higher ZrC content resulting in higher recrystallization temperatures. Specifically, the addition of 1.5 wt% ZrC increased the recrystallization finishing temperature from 700 °C to 1000 °C. ZrC delays the initiation and completion of recrystallization as well as the onset and termination of grain growth, with higher ZrC content leading to more pronounced delaying effects and extended incubation periods for recrystallization. Furthermore, ZrC influences recovery and recrystallization by affecting the precipitation of M<sub>23</sub>C<sub>6</sub> and Al<sub>2</sub>O<sub>3</sub>. ZrC addition also significantly enhances both room-temperature (RT) and high-temperature strength of the alloys. While low ZrC content markedly improves ductility, excessive ZrC content can impair it. The FeCrAl alloy with 0.5 wt% ZrC exhibited the best comprehensive mechanical properties. Moreover, with increasing ZrC content, the fracture mode of the alloy shifts from ductile to brittle fracture.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114547"},"PeriodicalIF":4.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A comparative study to understand the influence of processing conditions on the microstructural and phase evolution in HT9 ferritic/martensitic (F/M) steels, fabricated using laser powder bed fusion and laser directed energy deposition methods, was undertaken. The microstructural and phase evolutions during the laser-based additive manufacturing processes were compared with the HT9 steel fabricated using conventional vacuum arc melting and explained through the thermokinetic conditions associated with these manufacturing processes. Electron back scattered diffraction microstructures of the cross-sections reveal that the L-PBF processed HT9 steel microstructures comprised δ-ferrite, martensite (α’) and retained austenite (γ), whereas the L-DED microstructure consisted of α’ and retained γ, and no evidence of retained δ-ferrite was found. The arc melted steel showed predominantly martensite and a small amount of retained δ-ferrite. The L-PBF and L-DED microstructures comprise 15–21 % and 3–5 % of retained γ along the build direction, respectively. A multiscale multiphysics thermal model approach was adopted to deduce the correlation between the experimentally observed phase fractions and process-induced thermo-kinetics. The nanoindentation based hardness and yield stress obtained through spherical indentation technique, correlates well with the fraction of retained austenite. The experimental findings coupled with modelling aspects offer valuable insights into the intricate interplay between processing routes, phase evolution, and mechanical attributes in HT9 steel.
{"title":"Evolution of microstructures in laser additive manufactured HT-9 ferritic martensitic steel","authors":"Madhavan Radhakrishnan , Shashank Sharma , Selvamurugan Palaniappan , Narendra B. Dahotre","doi":"10.1016/j.matchar.2024.114551","DOIUrl":"10.1016/j.matchar.2024.114551","url":null,"abstract":"<div><div>A comparative study to understand the influence of processing conditions on the microstructural and phase evolution in HT9 ferritic/martensitic (F/M) steels, fabricated using laser powder bed fusion and laser directed energy deposition methods, was undertaken. The microstructural and phase evolutions during the laser-based additive manufacturing processes were compared with the HT9 steel fabricated using conventional vacuum arc melting and explained through the thermokinetic conditions associated with these manufacturing processes. Electron back scattered diffraction microstructures of the cross-sections reveal that the L-PBF processed HT9 steel microstructures comprised δ-ferrite, martensite (α’) and retained austenite (γ), whereas the L-DED microstructure consisted of α’ and retained γ, and no evidence of retained δ-ferrite was found. The arc melted steel showed predominantly martensite and a small amount of retained δ-ferrite. The L-PBF and L-DED microstructures comprise 15–21 % and 3–5 % of retained γ along the build direction, respectively. A multiscale multiphysics thermal model approach was adopted to deduce the correlation between the experimentally observed phase fractions and process-induced thermo-kinetics. The nanoindentation based hardness and yield stress obtained through spherical indentation technique, correlates well with the fraction of retained austenite. The experimental findings coupled with modelling aspects offer valuable insights into the intricate interplay between processing routes, phase evolution, and mechanical attributes in HT9 steel.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114551"},"PeriodicalIF":4.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1016/j.matchar.2024.114552
Tiantian Wang , Wentao Jiang , Xiaohong Wang , Bo Jiang , Ye Wang , Xin Wang , Hongyu Xu , Maoliang Hu , Dongdong Zhu
A new lightweight refractory high-entropy alloys were prepared by introducing Si element into AlMo0.5NbTiV alloy. The effects of Si content on microstructural evolution, density and high temperature mechanical properties were analyzed. The results show that the addition of Si leads to the formation of hard and brittle M5Si3-type (M = Ti and Nb) phase at the grain boundary of the matrix, which gradually transforms the alloys from a single body centered cubic (BCC) structure to a dual-phase structure. While the density of AlMo0.5NbTiVSix alloys decreases from 6.01 to 5.59 g/cm3 with the increase of Si content, and the mechanical properties are also significantly improved, AlMo0.5NbTiVSi0.5 alloy has the best yield strength of 1428 and 390 MPa at 1073 K and 1273 K, respectively. Among them, AlMo0.5NbTiVSi0.1 alloy has the best compression ductility strain at 1073 K, up to 22.2 %, indicating that the addition of appropriate Si can improve the compression ductility of the alloy, which is also caused by the combination of grain refinement and the appearance of eutectic structure. On the one hand, the segregation of Si elements at grain boundaries results in slow growth of the primary crystal, which inhibits the growth of grains. On the other hand, the eutectic structure composed of M5Si3 and BCC is distributed at the grain boundary, which is not conducive to the growth of grains, and the combined effect of the two eventually leads to the grain refinement. The strengthening mechanisms of the alloys can be attributed to the second phase strengthening, solid solution strengthening and grain refinement strengthening. In addition, the softening of the alloys at 1273 K is caused by dynamic recovery and dynamic recrystallization, and the dynamic recovery is the main softening mechanism.
通过在 AlMo0.5NbTiV 合金中引入硅元素，制备了一种新型轻质耐火高熵合金。分析了硅含量对微观结构演变、密度和高温力学性能的影响。结果表明，Si 的加入导致在基体晶界形成硬脆的 M5Si3 型（M = Ti 和 Nb）相，使合金从单体中心立方（BCC）结构逐渐转变为双相结构。随着 Si 含量的增加，AlMo0.5NbTiVSix 合金的密度从 6.01 g/cm3 降至 5.59 g/cm3，力学性能也得到显著改善，其中 AlMo0.5NbTiVSi0.5 合金的屈服强度最好，在 1073 K 和 1273 K 条件下分别达到 1428 和 390 MPa。其中，AlMo0.5NbTiVSi0.1 合金在 1073 K 时的压缩延性应变最好，高达 22.2%，这表明添加适当的 Si 可以提高合金的压缩延性，这也是晶粒细化和共晶结构出现的共同作用所致。一方面，硅元素在晶界的偏析导致主晶生长缓慢，从而抑制了晶粒的生长。另一方面，由 M5Si3 和 BCC 组成的共晶结构分布在晶界处，不利于晶粒的生长，二者的共同作用最终导致晶粒细化。合金的强化机制可归结为第二相强化、固溶强化和晶粒细化强化。此外，合金在 1273 K 时的软化是由动态恢复和动态再结晶引起的，动态恢复是主要的软化机制。
{"title":"Enhanced mechanical properties of lightweight refractory high-entropy alloys at elevated temperatures via Si addition","authors":"Tiantian Wang , Wentao Jiang , Xiaohong Wang , Bo Jiang , Ye Wang , Xin Wang , Hongyu Xu , Maoliang Hu , Dongdong Zhu","doi":"10.1016/j.matchar.2024.114552","DOIUrl":"10.1016/j.matchar.2024.114552","url":null,"abstract":"<div><div>A new lightweight refractory high-entropy alloys were prepared by introducing Si element into AlMo<sub>0.5</sub>NbTiV alloy. The effects of Si content on microstructural evolution, density and high temperature mechanical properties were analyzed. The results show that the addition of Si leads to the formation of hard and brittle M<sub>5</sub>Si<sub>3</sub>-type (M = Ti and Nb) phase at the grain boundary of the matrix, which gradually transforms the alloys from a single body centered cubic (BCC) structure to a dual-phase structure. While the density of AlMo<sub>0.5</sub>NbTiVSi<sub>x</sub> alloys decreases from 6.01 to 5.59 g/cm<sup>3</sup> with the increase of Si content, and the mechanical properties are also significantly improved, AlMo<sub>0.5</sub>NbTiVSi<sub>0.5</sub> alloy has the best yield strength of 1428 and 390 MPa at 1073 K and 1273 K, respectively. Among them, AlMo<sub>0.5</sub>NbTiVSi<sub>0.1</sub> alloy has the best compression ductility strain at 1073 K, up to 22.2 %, indicating that the addition of appropriate Si can improve the compression ductility of the alloy, which is also caused by the combination of grain refinement and the appearance of eutectic structure. On the one hand, the segregation of Si elements at grain boundaries results in slow growth of the primary crystal, which inhibits the growth of grains. On the other hand, the eutectic structure composed of M<sub>5</sub>Si<sub>3</sub> and BCC is distributed at the grain boundary, which is not conducive to the growth of grains, and the combined effect of the two eventually leads to the grain refinement. The strengthening mechanisms of the alloys can be attributed to the second phase strengthening, solid solution strengthening and grain refinement strengthening. In addition, the softening of the alloys at 1273 K is caused by dynamic recovery and dynamic recrystallization, and the dynamic recovery is the main softening mechanism.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114552"},"PeriodicalIF":4.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.matchar.2024.114553
Can Wang , Daibo Zhu , Wenming Zhu , Hailin Liu , Xinyan Liu , Xiaoyu Jiang , Fan Zhou , Yanbin Jiang , Xiaochen Ding , Tao Deng
This study examines the impact of varying Be contents on the evolution of secondary electron emission (SEE) properties. Through microscopic characterization of the microstructure before and after activation, it was determined that the phase composition was α(Cu) phase and eutectic structure (α(Cu) + γ). The findings indicate that as the Be content increased from 2.8 wt.% to 3.8 wt.%, the proportion of heterogeneous structures increased and the distribution became more uniform. Meanwhile, the number of heterogeneous structure interfaces between α(Cu) phase and γ phase increased, and there were a large number of mismatch dislocations at the interfaces, which served as short-circuit diffusion paths for Be elements. Be elements were more easily able to diffuse outward through the interface to form a uniform BeO film, thereby increasing secondary electron yield (SEY). In addition, the density of mismatch dislocations near the interface was high, promoting the formation of grain boundaries, which provided more diffusion pathways, allowing Be elements to diffuse outward more easily, thereby generating a uniform BeO film with increased SEY. This study holds significant implications for augmenting the SEY of CuBe dynode electrodes used in photomultiplier tubes (PMTs).
本研究探讨了不同铍含量对二次电子发射（SEE）特性演变的影响。通过对活化前后的微观结构进行表征，确定了相组成为 α(Cu) 相和共晶结构 (α(Cu) + γ)。研究结果表明，随着 Be 含量从 2.8 wt.% 增加到 3.8 wt.%，异质结构的比例增加，分布更加均匀。同时，α（Cu）相和γ相之间的异质结构界面数量增加，界面上存在大量错配位错，成为 Be 元素的短路扩散路径。Be 元素更容易通过界面向外扩散，形成均匀的 BeO 薄膜，从而提高了二次电子产率（SEY）。此外，界面附近的错配位错密度很高，促进了晶界的形成，从而提供了更多的扩散途径，使 Be 元素更容易向外扩散，从而生成了均匀的 BeO 薄膜，提高了 SEY。这项研究对于提高光电倍增管（PMT）中使用的铜铍阳极电极的 SEY 有着重要的意义。
{"title":"Comprehensive analysis of beryllium content influence on secondary electron yield in CuBe alloys","authors":"Can Wang , Daibo Zhu , Wenming Zhu , Hailin Liu , Xinyan Liu , Xiaoyu Jiang , Fan Zhou , Yanbin Jiang , Xiaochen Ding , Tao Deng","doi":"10.1016/j.matchar.2024.114553","DOIUrl":"10.1016/j.matchar.2024.114553","url":null,"abstract":"<div><div>This study examines the impact of varying Be contents on the evolution of secondary electron emission (SEE) properties. Through microscopic characterization of the microstructure before and after activation, it was determined that the phase composition was <em>α</em>(Cu) phase and eutectic structure (<em>α</em>(Cu) + <em>γ</em>). The findings indicate that as the Be content increased from 2.8 wt.% to 3.8 wt.%, the proportion of heterogeneous structures increased and the distribution became more uniform. Meanwhile, the number of heterogeneous structure interfaces between <em>α</em>(Cu) phase and <em>γ</em> phase increased, and there were a large number of mismatch dislocations at the interfaces, which served as short-circuit diffusion paths for Be elements. Be elements were more easily able to diffuse outward through the interface to form a uniform BeO film, thereby increasing secondary electron yield (SEY). In addition, the density of mismatch dislocations near the interface was high, promoting the formation of grain boundaries, which provided more diffusion pathways, allowing Be elements to diffuse outward more easily, thereby generating a uniform BeO film with increased SEY. This study holds significant implications for augmenting the SEY of Cu<img>Be dynode electrodes used in photomultiplier tubes (PMTs).</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114553"},"PeriodicalIF":4.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-12DOI: 10.1016/j.matchar.2024.114549
Penghui Li , Wang Tang , Qihang Shen , Xiaobin Shi , Ping Liu
The effect of aging treatment on the microstructure, phase transformation behavior and mechanical properties of nanocrystalline NiTi alloy was studied. The nanocrystalline NiTi alloys with different grain sizes were acquired by cold drawing followed by annealing at 350–500 °C for 10 min. The annealed samples were aged at 250–400 °C for 48 h. The Ti3Ni4 precipitates were found in aged nanocrystalline NiTi alloys. In the sample with smaller average nanograin size, the precipitates were found at the edge of grain boundaries and little lattice strain was shown in R phase matrix. In the sample with larger average grain size, the precipitates were found in the nanograins and exhibited a coherent interface with the matrix. The nanocrystalline R phase NiTi matrix exhibited a significant compressive stress at the end of the coherent precipitate. The coherent precipitates in sample aged at 250 °C after annealing at 500 °C suppress the stress-induced R → B19′ phase transformation and increased the upper plateau stress. The precipitation in sample aged at 250 °C after annealing at 350 °C unable to suppress the martensitic transformation effectively.
研究了时效处理对纳米晶镍钛合金微观结构、相变行为和力学性能的影响。不同晶粒大小的纳米晶镍钛合金是通过冷拔获得的，然后在 350-500 °C 下退火 10 分钟。退火后的样品在 250-400 ℃ 下进行 48 小时的时效处理。在平均纳米晶粒尺寸较小的样品中，析出物出现在晶界边缘，R 相基体中的晶格应变很小。在平均晶粒尺寸较大的样品中，析出物出现在纳米晶粒中，并与基体呈现出一致的界面。纳米晶 R 相镍钛基体在相干析出物末端表现出显著的压应力。在 500 °C 退火后于 250 °C 老化的样品中的相干析出物抑制了应力诱导的 R → B19′ 相变，并增加了上平台应力。350 ℃退火后 250 ℃老化的样品中的析出物无法有效抑制马氏体转变。
{"title":"Effect of grain size on precipitation and microstrain of nanocrystalline NiTi alloys","authors":"Penghui Li , Wang Tang , Qihang Shen , Xiaobin Shi , Ping Liu","doi":"10.1016/j.matchar.2024.114549","DOIUrl":"10.1016/j.matchar.2024.114549","url":null,"abstract":"<div><div>The effect of aging treatment on the microstructure, phase transformation behavior and mechanical properties of nanocrystalline NiTi alloy was studied. The nanocrystalline NiTi alloys with different grain sizes were acquired by cold drawing followed by annealing at 350–500 °C for 10 min. The annealed samples were aged at 250–400 °C for 48 h. The Ti<sub>3</sub>Ni<sub>4</sub> precipitates were found in aged nanocrystalline NiTi alloys. In the sample with smaller average nanograin size, the precipitates were found at the edge of grain boundaries and little lattice strain was shown in R phase matrix. In the sample with larger average grain size, the precipitates were found in the nanograins and exhibited a coherent interface with the matrix. The nanocrystalline R phase NiTi matrix exhibited a significant compressive stress at the end of the coherent precipitate. The coherent precipitates in sample aged at 250 °C after annealing at 500 °C suppress the stress-induced R → B19′ phase transformation and increased the upper plateau stress. The precipitation in sample aged at 250 °C after annealing at 350 °C unable to suppress the martensitic transformation effectively.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114549"},"PeriodicalIF":4.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Precipitation directly determines the high-temperature properties of the austenitic heat-resistant steels. The precipitations of MX, Z-phase, M23C6 and σ-phase, ranging from micrometers to nanometers, are commonly characterized using the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). However, details of their evolution behavior are still unclear due to the limited SEM resolution using the traditional sampling method and the limited spatial resolution of TEM. In this work, field emission SEM-based electron channel contrast imaging (ECCI) techniques with flexible sampling routes were introduced to observe the precipitation evolution behavior of HR3C steel after aging at 700 °C for 8095 h. We showed that the coarse primary-MX and Z-phase in the as-received steel are relatively stable during aging. The coarse M23C6 and tiny secondary Z-phase dispersions were rapidly formed along the grain/twin boundaries and within dislocation arrays inside the grain interior, respectively. We further found that the M23C6 at grain boundaries would change from continuous to semi-continuous due to the formation of σ-phases, while in twin boundaries, it would become continuous over aging. Moreover, we showed that the σ-phases were in-situ transformed from M23C6 at the grain boundaries via its dissolution, facilitating the nucleation of tiny Z-phase inside the σ-phase grains, and this phenomenon has not been reported so far. We have demonstrated that ECCI with an electrolytic-polishing-based sampling route is effective in revealing multi-scale precipitation with high-throughput efficiency, and it allows the direct observation of the complex behavior of precipitates down to the nanoscale using a bulk sample. This method can be used as an efficient way for the quantitative microstructure study.
析出物直接决定了奥氏体耐热钢的高温性能。通常使用扫描电子显微镜（SEM）和透射电子显微镜（TEM）对 MX、Z 相、M23C6 和 σ 相的析出物（从微米到纳米）进行表征。然而，由于使用传统取样方法的扫描电子显微镜分辨率有限，而透射电子显微镜的空间分辨率也有限，因此它们的演化行为细节仍不清楚。本研究采用基于场发射扫描电镜的电子通道对比成像（ECCI）技术和灵活的取样路径，观察了 HR3C 钢在 700 °C 时效 8095 h 后的析出演化行为。粗大的 M23C6 和微小的次生 Z 相分别沿着晶粒/孪晶边界和晶粒内部的位错阵列迅速形成。我们进一步发现，由于σ相的形成，晶界处的 M23C6 将从连续变为半连续，而在孪晶边界，随着老化的进行，M23C6 将变为连续。此外，我们还发现σ相是由 M23C6 通过溶解在晶界处原位转化而来的，从而促进了σ相晶粒内部微小 Z 相的成核，而这一现象迄今尚未见报道。我们已经证明，基于电解抛光取样途径的 ECCI 能以高通量的效率有效揭示多尺度沉淀，并能利用块体样品直接观察沉淀物直至纳米尺度的复杂行为。这种方法可作为定量微观结构研究的有效途径。
{"title":"Direct observation of the evolution behavior of micro to nanoscale precipitates in austenitic heat-resistant steel via electron channeling contrast imaging","authors":"Hongyu Zhou , Yuchen Zhao , Zhangjian Zhou , Wenyue Zheng , Yinsheng He","doi":"10.1016/j.matchar.2024.114550","DOIUrl":"10.1016/j.matchar.2024.114550","url":null,"abstract":"<div><div>Precipitation directly determines the high-temperature properties of the austenitic heat-resistant steels. The precipitations of MX, <em>Z</em>-phase, M<sub>23</sub>C<sub>6</sub> and σ-phase, ranging from micrometers to nanometers, are commonly characterized using the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). However, details of their evolution behavior are still unclear due to the limited SEM resolution using the traditional sampling method and the limited spatial resolution of TEM. In this work, field emission SEM-based electron channel contrast imaging (ECCI) techniques with flexible sampling routes were introduced to observe the precipitation evolution behavior of HR3C steel after aging at 700 °C for 8095 h. We showed that the coarse primary-MX and <em>Z</em>-phase in the as-received steel are relatively stable during aging. The coarse M<sub>23</sub>C<sub>6</sub> and tiny secondary Z-phase dispersions were rapidly formed along the grain/twin boundaries and within dislocation arrays inside the grain interior, respectively. We further found that the M<sub>23</sub>C<sub>6</sub> at grain boundaries would change from continuous to semi-continuous due to the formation of σ-phases, while in twin boundaries, it would become continuous over aging. Moreover, we showed that the σ-phases were in-situ transformed from M<sub>23</sub>C<sub>6</sub> at the grain boundaries via its dissolution, facilitating the nucleation of tiny <em>Z</em>-phase inside the σ-phase grains, and this phenomenon has not been reported so far. We have demonstrated that ECCI with an electrolytic-polishing-based sampling route is effective in revealing multi-scale precipitation with high-throughput efficiency, and it allows the direct observation of the complex behavior of precipitates down to the nanoscale using a bulk sample. This method can be used as an efficient way for the quantitative microstructure study.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114550"},"PeriodicalIF":4.8,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-10DOI: 10.1016/j.matchar.2024.114546
Jin Wang , Yun Bai , Feilong Zhang , Zexin Qi , Wei Liu , Qiang Liu , Shufeng Yang , Jingshe Li
This study investigates the precipitation characteristics of sulfide inclusions during the solidification of alloy steels under the combined influence of sulfur (S), manganese (Mn), and tellurium (Te). A multidimensional characterization and comparison of sulfide inclusions in Te-containing steels with varying S content and cooling conditions were performed using X-ray Micro-CT, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Both 2D and 3D analyses confirmed that increasing the S content in Te-containing steels leads to a higher overall number of sulfide inclusions. In particular, the rise in the proportion of small-sized inclusions was analyzed from the perspectives of interfacial dynamics and equilibrium thermodynamics. Regarding inclusion morphology, 2D characterization exhibited significant inaccuracies in assessing large inclusions in high-S, Te-containing steels, while X-ray Micro-CT proved advantageous for evaluating both the spatial distribution and morphology of inclusions. In addition, X-ray Micro-CT was used for the first time in this study to perform a non-destructive analysis of the layered MnS-MnTe structure, expanding the method's application in the metallurgical field. A predictive model based on inter-element activity interaction coefficients was employed to determine the first-order activity interaction coefficient of Te for Mn. Furthermore, a thermodynamic model for sulfide precipitation in Te-containing steels was developed. This study lays a theoretical foundation for better control of sulfide inclusions in future Te-containing specialty steels.
本研究探讨了在硫（S）、锰（Mn）和碲（Te）的共同影响下，合金钢凝固过程中硫化物夹杂物的析出特征。利用 X 射线显微 CT、拉曼光谱和场发射扫描电子显微镜 (FE-SEM) 对不同 S 含量和冷却条件下的含碲钢中的硫化物夹杂物进行了多维表征和比较。二维和三维分析证实，含钛钢中 S 含量的增加会导致硫化物夹杂物的总体数量增加。特别是从界面动力学和平衡热力学的角度分析了小尺寸夹杂物比例的增加。在夹杂物形态方面，二维表征在评估高硫、含钛钢中的大型夹杂物时表现出明显的不准确性，而 X 射线显微 CT 则在评估夹杂物的空间分布和形态方面具有优势。此外，本研究首次使用 X 射线显微 CT 对层状 MnS-MnTe 结构进行了无损分析，从而扩大了该方法在冶金领域的应用。研究采用了一个基于元素间活性相互作用系数的预测模型，以确定钛对锰的一阶活性相互作用系数。此外，还建立了含钛钢中硫化物沉淀的热力学模型。这项研究为更好地控制未来含钛特种钢中的硫化物夹杂物奠定了理论基础。
{"title":"Theoretical precipitation modeling and multidimensional characterization of sulfide inclusions in tellurium-containing steels","authors":"Jin Wang , Yun Bai , Feilong Zhang , Zexin Qi , Wei Liu , Qiang Liu , Shufeng Yang , Jingshe Li","doi":"10.1016/j.matchar.2024.114546","DOIUrl":"10.1016/j.matchar.2024.114546","url":null,"abstract":"<div><div>This study investigates the precipitation characteristics of sulfide inclusions during the solidification of alloy steels under the combined influence of sulfur (S), manganese (Mn), and tellurium (Te). A multidimensional characterization and comparison of sulfide inclusions in Te-containing steels with varying S content and cooling conditions were performed using X-ray Micro-CT, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Both 2D and 3D analyses confirmed that increasing the S content in Te-containing steels leads to a higher overall number of sulfide inclusions. In particular, the rise in the proportion of small-sized inclusions was analyzed from the perspectives of interfacial dynamics and equilibrium thermodynamics. Regarding inclusion morphology, 2D characterization exhibited significant inaccuracies in assessing large inclusions in high-S, Te-containing steels, while X-ray Micro-CT proved advantageous for evaluating both the spatial distribution and morphology of inclusions. In addition, X-ray Micro-CT was used for the first time in this study to perform a non-destructive analysis of the layered MnS-MnTe structure, expanding the method's application in the metallurgical field. A predictive model based on inter-element activity interaction coefficients was employed to determine the first-order activity interaction coefficient of Te for Mn. Furthermore, a thermodynamic model for sulfide precipitation in Te-containing steels was developed. This study lays a theoretical foundation for better control of sulfide inclusions in future Te-containing specialty steels.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114546"},"PeriodicalIF":4.8,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-09DOI: 10.1016/j.matchar.2024.114530
Ya Yang , Fei Zhao , Dongbing Cui , Yuanbiao Tan
In this present paper, a biodegradable Zn-xCu alloys with an ultrahigh strength and ductility can be achieved via hot-rolling and tailoring Cu concentration, and the role of Cu concentration on the microstructure and texture evolution in the Zn-xCu alloys during hot-rolling were investigated by XRD, EBSD and TEM analysis. The results show that the microstructure of as-cast Zn-xCu alloys consisted of large sized CuZn5 phase and Zn matrix grains before hot-rolling, and numerous submicron CuZn5 phase can dynamically precipitate during hot-rolling of Zn-xCu alloys. The existence of CuZn5 phase can result in the particle stimulated nucleation of recrystallization (PSN), and then result in the formation of fine recrystallized grains. Moreover, three texture components including , and textures can form in the Zn-xCu alloys after hot-rolling. With boosting Cu concentration, the intensity of texture gradually reduced, while the intensity of and texture components firstly raised with the augment of Cu concentration, and then reduced. For the Zn-xCu alloys with 8 wt%Cu concentration, a combination of high yield strength, ultimate tensile strength and elongation (269.7 MPa, 322.9 MPa and 26.3 %) can be achieved, which can meet the high-performance demands of biodegradable metal vascular stents.
本文通过热轧和定制 Cu 浓度的方法获得了一种具有超高强度和延展性的可生物降解 Zn-xCu 合金，并通过 XRD、EBSD 和 TEM 分析研究了热轧过程中 Cu 浓度对 Zn-xCu 合金微观结构和纹理演变的影响。结果表明，热轧前 Zn-xCu 合金的铸态微观结构由大尺寸的 CuZn5 相和 Zn 基体晶粒组成，在 Zn-xCu 合金热轧过程中会动态析出大量亚微米级的 CuZn5 相。CuZn5 相的存在会导致颗粒刺激再结晶成核（PSN），进而形成细小的再结晶晶粒。此外，Zn-xCu 合金在热轧后可形成三种织构成分，包括 0001<112'0>、101'1<1'012>和 112'0<0001>织构。随着 Cu 浓度的增加，112'0<0001>纹理强度逐渐减弱，而 0001<112'0> 和 101'1<1'012>纹理成分的强度则先随 Cu 浓度的增加而增强，然后减弱。对于铜浓度为 8 wt% 的 Zn-xCu 合金，可以获得较高的屈服强度、极限拉伸强度和伸长率（分别为 269.7 MPa、322.9 MPa 和 26.3%），可以满足可降解金属血管支架的高性能要求。
{"title":"Achieving ultrahigh strength and ductility in biodegradable Zn-xCu alloys via hot-rolling and tailoring Cu concentration","authors":"Ya Yang , Fei Zhao , Dongbing Cui , Yuanbiao Tan","doi":"10.1016/j.matchar.2024.114530","DOIUrl":"10.1016/j.matchar.2024.114530","url":null,"abstract":"<div><div>In this present paper, a biodegradable Zn-<em>x</em>Cu alloys with an ultrahigh strength and ductility can be achieved via hot-rolling and tailoring Cu concentration, and the role of Cu concentration on the microstructure and texture evolution in the Zn-<em>x</em>Cu alloys during hot-rolling were investigated by XRD, EBSD and TEM analysis. The results show that the microstructure of as-cast Zn-<em>x</em>Cu alloys consisted of large sized CuZn<sub>5</sub> phase and Zn matrix grains before hot-rolling, and numerous submicron CuZn<sub>5</sub> phase can dynamically precipitate during hot-rolling of Zn-<em>x</em>Cu alloys. The existence of CuZn<sub>5</sub> phase can result in the particle stimulated nucleation of recrystallization (PSN), and then result in the formation of fine recrystallized grains. Moreover, three texture components including <span><math><mfenced><mn>0001</mn></mfenced><mo><</mo><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>0</mn><mo>></mo></math></span>, <span><math><mfenced><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn></mrow></mfenced><mo><</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>012</mn><mo>></mo></math></span> and <span><math><mfenced><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>0</mn></mrow></mfenced><mo><</mo><mn>0001</mn><mo>></mo></math></span> textures can form in the Zn-<em>x</em>Cu alloys after hot-rolling. With boosting Cu concentration, the intensity of <span><math><mfenced><mrow><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>0</mn></mrow></mfenced><mo><</mo><mn>0001</mn><mo>></mo></math></span> texture gradually reduced, while the intensity of <span><math><mfenced><mn>0001</mn></mfenced><mo><</mo><mn>11</mn><mover><mn>2</mn><mo>¯</mo></mover><mn>0</mn><mo>></mo></math></span> and <span><math><mfenced><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn></mrow></mfenced><mo><</mo><mover><mn>1</mn><mo>¯</mo></mover><mn>012</mn><mo>></mo></math></span> texture components firstly raised with the augment of Cu concentration, and then reduced. For the Zn-<em>x</em>Cu alloys with 8 wt%Cu concentration, a combination of high yield strength, ultimate tensile strength and elongation (269.7 MPa, 322.9 MPa and 26.3 %) can be achieved, which can meet the high-performance demands of biodegradable metal vascular stents.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114530"},"PeriodicalIF":4.8,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-09DOI: 10.1016/j.matchar.2024.114515
Wenlong Zhu , Huabing Liu , Shilong Xing , Chuanhai Jiang , Vincent Ji
Shot peening (SP) is recognized for its capacity to enhance surface strength and induce compressive residual stresses (CRS). Nevertheless, quantifying the mechanical property improvements in thin shot peened layers remains challenging with traditional methods. In this study, CNT/Al-Cu-Mg composites were subjected to shot peening. The microstructure evolution of the peened layers along the layer depth direction was investigated by XRD and TEM. Meanwhile, the changes in the mechanical properties of the shot peened layers and the release rules of CRS during tensile cycling at different numbers loads were measured by an in-situ X-ray stress analyzer and a micro-tensile device in conjunction with the Von Mises stress criterion. The results showed that SP generated the nano-gradient deformation layer with nanograins size of 50–100 nm near the surface. The yield strength of the surface layer was increased from 352 MPa before SP to 435 MPa, an increase of 23.6 %. Moreover, the observation of fracture morphology indicated that SP reduced the material plasticit moderately and the agglomeration of the Al2Cu. In addition, in the case of a certain CRS on the initial surface, the relaxation of CRS was correlated with the magnitude of applied loads and the number of cycles and couldn't occur when the applied loads is below a specific value.
{"title":"Surface mechanical property and residual stress stability of nanostructured CNT/Al-Cu-Mg composites induced by shot peening","authors":"Wenlong Zhu , Huabing Liu , Shilong Xing , Chuanhai Jiang , Vincent Ji","doi":"10.1016/j.matchar.2024.114515","DOIUrl":"10.1016/j.matchar.2024.114515","url":null,"abstract":"<div><div>Shot peening (SP) is recognized for its capacity to enhance surface strength and induce compressive residual stresses (CRS). Nevertheless, quantifying the mechanical property improvements in thin shot peened layers remains challenging with traditional methods. In this study, CNT/Al-Cu-Mg composites were subjected to shot peening. The microstructure evolution of the peened layers along the layer depth direction was investigated by XRD and TEM. Meanwhile, the changes in the mechanical properties of the shot peened layers and the release rules of CRS during tensile cycling at different numbers loads were measured by an in-situ X-ray stress analyzer and a micro-tensile device in conjunction with the Von Mises stress criterion. The results showed that SP generated the nano-gradient deformation layer with nanograins size of 50–100 nm near the surface. The yield strength of the surface layer was increased from 352 MPa before SP to 435 MPa, an increase of 23.6 %. Moreover, the observation of fracture morphology indicated that SP reduced the material plasticit moderately and the agglomeration of the Al<sub>2</sub>Cu. In addition, in the case of a certain CRS on the initial surface, the relaxation of CRS was correlated with the magnitude of applied loads and the number of cycles and couldn't occur when the applied loads is below a specific value.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114515"},"PeriodicalIF":4.8,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-08DOI: 10.1016/j.matchar.2024.114540
Bo Yang , Baoxi Liu , Zhichao Luo , Hui Yu , Fuxing Yin
In this paper, the microstructure evolution and mechanical properties of low carbon steels during direct quenched and rolling followed by water-cooled processes were studied. Two experimental steels, which were directly quenched at 900 °C (Q900) and 1000 °C (Q1000), were compared with steels that were water-cooled after rolling at the same temperatures (R900 and R1000). Microstructural analyses using EBSD and TEM revealed that rolling reduced the size of prior austenite grains (PAGs), resulting in an average width of 3.6 μm, which influenced grain boundary distributions and variant selection. The best combination of strength, ductility and toughness was obtained in R900 steel, including tensile (with the yield strength of 1304 MPa, the total elongation of 22.95 %), Charpy impact (with the impact energy at 20 °C is 182 J), and fracture toughness evaluations (with the is 326.28 KJ/m2), this demonstrates that R900 steel exhibited significantly enhanced strength and ductility compared to Q900 steel. Moreover, EBSD analysis of crack propagation paths highlighted the role of high-angle grain boundaries (HAGBs) in enhancing fracture toughness by deflecting cracks. These findings underscore the critical role of PAGs size in tailoring microstructures to achieve superior mechanical properties in low carbon martensitic steels, offering insights for advanced material design and application in demanding structural and industrial contexts.
Keyworks.
low-carbon martensitic steel; strength and toughness; martensitic transformation; ductile-to-brittle transition phenomenon; selection of martensitic variants.
{"title":"Design and control the selection of martensitic variant to simultaneously improve strength and toughness of low-carbon martensitic steel","authors":"Bo Yang , Baoxi Liu , Zhichao Luo , Hui Yu , Fuxing Yin","doi":"10.1016/j.matchar.2024.114540","DOIUrl":"10.1016/j.matchar.2024.114540","url":null,"abstract":"<div><div>In this paper, the microstructure evolution and mechanical properties of low carbon steels during direct quenched and rolling followed by water-cooled processes were studied. Two experimental steels, which were directly quenched at 900 °C (Q900) and 1000 °C (Q1000), were compared with steels that were water-cooled after rolling at the same temperatures (R900 and R1000). Microstructural analyses using EBSD and TEM revealed that rolling reduced the size of prior austenite grains (PAGs), resulting in an average width of 3.6 μm, which influenced grain boundary distributions and variant selection. The best combination of strength, ductility and toughness was obtained in R900 steel, including tensile (with the yield strength of 1304 MPa, the total elongation of 22.95 %), Charpy impact (with the impact energy at 20 °C is 182 J), and fracture toughness evaluations (with the <span><math><msub><mi>J</mi><mrow><mn>1</mn><mi>c</mi></mrow></msub></math></span> is 326.28 KJ/m<sup>2</sup>), this demonstrates that R900 steel exhibited significantly enhanced strength and ductility compared to Q900 steel. Moreover, EBSD analysis of crack propagation paths highlighted the role of high-angle grain boundaries (HAGBs) in enhancing fracture toughness by deflecting cracks. These findings underscore the critical role of PAGs size in tailoring microstructures to achieve superior mechanical properties in low carbon martensitic steels, offering insights for advanced material design and application in demanding structural and industrial contexts.</div><div><strong>Keyworks.</strong></div><div>low-carbon martensitic steel; strength and toughness; martensitic transformation; ductile-to-brittle transition phenomenon; selection of martensitic variants.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114540"},"PeriodicalIF":4.8,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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