Pub Date : 2024-10-01DOI: 10.1016/j.matchar.2024.114420
Lin Hong , Hongjun Li , Ming Huang , Yuan Qin , Shiyu Xu , Sen Yang
In the present study, to improve the performances of Al0.3CoCrFeNi1.5 high entropy alloys (HEAs), grain boundary character distribution (GBCD) of Al0.3CoCrFeNi1.5 HEA has been optimized by an appropriate thermo-mechanical processing. The experiment results showed that the fraction of low-Σ coincidence site lattice (CSL) boundaries could reach approximately 80 % through cold rolling with deformation of 8 % and subsequent annealing at 1050 °C for 5 min. The reason for GBCD optimization could be attributed to sufficient strain-induced boundary migration (SIBM) or grain growth after recrystallization. While recrystallization is not favorable for optimizing GBCD. The mechanical properties and corrosion resistance have been enhanced, with a more pronounced improvement observed in the corrosion resistance. The corrosion current density icorr of the GBEM specimen stands at 0.23 μA∙cm−2, representing a reduction of 66 % in comparison to the BM specimen (0.68 μA∙cm−2). The improvement of corrosion resistance of Al0.3CoCrFeNi1.5 HEA resulted from the discontinuous random grain boundaries (RGBs) broken by the high fraction of low-ΣCSL boundaries, especially Σ3 boundaries suppressed the propagation of corrosion crack.
{"title":"Enhancing mechanical property and corrosion resistance of Al0.3CoCrFeNi1.5 high entropy alloy via grain boundary engineering","authors":"Lin Hong , Hongjun Li , Ming Huang , Yuan Qin , Shiyu Xu , Sen Yang","doi":"10.1016/j.matchar.2024.114420","DOIUrl":"10.1016/j.matchar.2024.114420","url":null,"abstract":"<div><div>In the present study, to improve the performances of Al<sub>0.3</sub>CoCrFeNi<sub>1.5</sub> high entropy alloys (HEAs), grain boundary character distribution (GBCD) of Al<sub>0.3</sub>CoCrFeNi<sub>1.5</sub> HEA has been optimized by an appropriate thermo-mechanical processing. The experiment results showed that the fraction of low-Σ coincidence site lattice (CSL) boundaries could reach approximately 80 % through cold rolling with deformation of 8 % and subsequent annealing at 1050 °C for 5 min. The reason for GBCD optimization could be attributed to sufficient strain-induced boundary migration (SIBM) or grain growth after recrystallization. While recrystallization is not favorable for optimizing GBCD. The mechanical properties and corrosion resistance have been enhanced, with a more pronounced improvement observed in the corrosion resistance. The corrosion current density i<sub>corr</sub> of the GBEM specimen stands at 0.23 μA∙cm<sup>−2</sup>, representing a reduction of 66 % in comparison to the BM specimen (0.68 μA∙cm<sup>−2</sup>). The improvement of corrosion resistance of Al<sub>0.3</sub>CoCrFeNi<sub>1.5</sub> HEA resulted from the discontinuous random grain boundaries (RGBs) broken by the high fraction of low-ΣCSL boundaries, especially Σ3 boundaries suppressed the propagation of corrosion crack.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114420"},"PeriodicalIF":4.8,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418171","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 : 2024-09-30DOI: 10.1016/j.matchar.2024.114423
Lei He , Wei Wei , He Zhang , Dan Lin , Fufa Wu , Hai Su , Xinhua Yang
AlCoCrFeNi2.1 hot-rolled eutectic high entropy alloys were welded by laser welding, yielding a free-defect laser-welded connection. With the use of optical microscopy, EDS, EBSD, and XRD, the microstructure of the base metal (BM), fusion zone (FZ), and heat-affected zone (HAZ) of the joint was examined. The produced joint underwent tensile and micro-hardness testing as well as a fracture morphology examination. A similar tensile strength in the FZ and BM is measured, while a decrease in the elongation. The typical layered lamellar structures, in particular an FCC + BCC dual-phase structure, were all visible in the HAZ, BM, and FZ zones. The α-fiber and γ-fiber as well as other textures are determined by the ODF figure, indicating a potential orientation distribution of the as-hot rolled AlCoCrFeNi2.1 joint. A clear grain refinement characteristics in the fusion zone as a result of the uneven thermal cycling during the welding process. The results of the mechanical test demonstrate the base metal has the highest hardness value, i.e. 500–550 HV0.2, within the welded joint zone. The welded joint has a tensile strength ∼1200 MPa, which is marginally higher than ∼1150 MPa in the base metal, and an elongation that decreases by 20 % from base metal to welded joint, indicating a decrease in the plasticity of the welded joint. A combination of brittle and ductile fracture occurs in welded joints during tensile failure. This study may give possibilities for the engineering application of laser welding of AlCoCrFeNi2.1 eutectic high entropy alloy in the future.
{"title":"The microstructure and mechanical properties of the laser-welded joints of as-hot rolled AlCoCrFeNi2.1 high entropy alloy","authors":"Lei He , Wei Wei , He Zhang , Dan Lin , Fufa Wu , Hai Su , Xinhua Yang","doi":"10.1016/j.matchar.2024.114423","DOIUrl":"10.1016/j.matchar.2024.114423","url":null,"abstract":"<div><div>AlCoCrFeNi<sub>2.1</sub> hot-rolled eutectic high entropy alloys were welded by laser welding, yielding a free-defect laser-welded connection. With the use of optical microscopy, EDS, EBSD, and XRD, the microstructure of the base metal (BM), fusion zone (FZ), and heat-affected zone (HAZ) of the joint was examined. The produced joint underwent tensile and micro-hardness testing as well as a fracture morphology examination. A similar tensile strength in the FZ and BM is measured, while a decrease in the elongation. The typical layered lamellar structures, in particular an FCC + BCC dual-phase structure, were all visible in the HAZ, BM, and FZ zones. The α-fiber and γ-fiber as well as other textures are determined by the ODF figure, indicating a potential orientation distribution of the as-hot rolled AlCoCrFeNi<sub>2.1</sub> joint. A clear grain refinement characteristics in the fusion zone as a result of the uneven thermal cycling during the welding process. The results of the mechanical test demonstrate the base metal has the highest hardness value, i.e. 500–550 HV<sub>0.2</sub>, within the welded joint zone. The welded joint has a tensile strength ∼1200 MPa, which is marginally higher than ∼1150 MPa in the base metal, and an elongation that decreases by 20 % from base metal to welded joint, indicating a decrease in the plasticity of the welded joint. A combination of brittle and ductile fracture occurs in welded joints during tensile failure. This study may give possibilities for the engineering application of laser welding of AlCoCrFeNi<sub>2.1</sub> eutectic high entropy alloy in the future.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114423"},"PeriodicalIF":4.8,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418170","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 : 2024-09-30DOI: 10.1016/j.matchar.2024.114419
Andrea Fazi , Pedro A. Ferreirós , Yanling Ge , Song Lu , Mattias Thuvander , Zaiqing Que
A full-scale dissimilar metal weld safe-end mock-up, precisely replicating a critical component of a modern nuclear power plant, was investigated. The brittle fracture behavior, carbide evolution and nanoscale elemental segregation in the heat-affected zone (HAZ) of low alloy steel (LAS) were analyzed under both post-weld heat-treated and thermally-aged conditions (400 °C for 15,000 h, equivalent to 90 years of operation) using analytical electron microscopy and atom probe tomography. The observed increase in grain boundary (GB) decohesion and intergranular cracking on the fracture surface and the decrease of fracture toughness are primarily attributed to P and Mn segregation to GBs and the coarsening of carbides upon long-term thermal aging. The direct observations of significant elemental segregation to GBs and the consequent reduction in fracture toughness in the HAZ are unexpected for modern low-phosphorus LASs, highlighting potential concerns for evaluating the structural integrity of modern nuclear power plants.
对精确复制现代核电厂关键部件的全尺寸异种金属焊接安全端模型进行了研究。利用分析电子显微镜和原子探针断层扫描技术，分析了低合金钢（LAS）在焊后热处理和热老化（400 °C，15,000 小时，相当于运行 90 年）条件下的脆性断裂行为、碳化物演变和热影响区（HAZ）中的纳米级元素偏析。所观察到的晶界（GB）脱粘和断裂表面晶间裂纹的增加以及断裂韧性的降低主要归因于 P 和 Mn 在 GB 上的偏析以及长期热老化后碳化物的粗化。对于现代低磷 LAS 而言，直接观察到大量元素偏析到 GB 以及 HAZ 断裂韧性随之降低是意料之外的，这凸显了评估现代核电站结构完整性的潜在问题。
{"title":"Unexpected thermal aging effect on brittle fracture and elemental segregation in modern dissimilar metal weld","authors":"Andrea Fazi , Pedro A. Ferreirós , Yanling Ge , Song Lu , Mattias Thuvander , Zaiqing Que","doi":"10.1016/j.matchar.2024.114419","DOIUrl":"10.1016/j.matchar.2024.114419","url":null,"abstract":"<div><div>A full-scale dissimilar metal weld safe-end mock-up, precisely replicating a critical component of a modern nuclear power plant, was investigated. The brittle fracture behavior, carbide evolution and nanoscale elemental segregation in the heat-affected zone (HAZ) of low alloy steel (LAS) were analyzed under both post-weld heat-treated and thermally-aged conditions (400 °C for 15,000 h, equivalent to 90 years of operation) using analytical electron microscopy and atom probe tomography. The observed increase in grain boundary (GB) decohesion and intergranular cracking on the fracture surface and the decrease of fracture toughness are primarily attributed to P and Mn segregation to GBs and the coarsening of carbides upon long-term thermal aging. The direct observations of significant elemental segregation to GBs and the consequent reduction in fracture toughness in the HAZ are unexpected for modern low-phosphorus LASs, highlighting potential concerns for evaluating the structural integrity of modern nuclear power plants.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114419"},"PeriodicalIF":4.8,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-30DOI: 10.1016/j.matchar.2024.114418
D.J. Sprouster , B. Adam , A. Koziol , L. Rolly , C. Huotilainen , J.D. Tucker
The ferritic-martensitic steel HT9 is a candidate material for fuel cladding and core components in advanced nuclear reactors, such as sodium-cooled fast reactors, thanks to their high temperature mechanical properties and low susceptibility to irradiation induced swelling phenomena. However, thermal stability and elevated temperature microstructural evolution in these alloys may impact their long-term behavior and reliability. In this work, the effects of thermal aging on the microstructural and mechanical properties of HT9 have been investigated through complementary electron microscopy, synchrotron X-ray diffraction, microhardness, and thermodynamic modeling. Plates of HT9 were aged up to 50 kh at relevant sodium-cooled fast reactor operational temperatures (360 °C - 700 °C). Trends in microstructure as a function of aging time and temperature were apparent from qualitative and quantitative analysis. These observations were further supported by thermodynamic modeling of the bulk and precipitate phases. Specific phases observed include BCC Fe, FCC M23C6, HCP and FCC MX phase and Laves M2X phase. Through the application of our multi-scale and multi-modal approach, clear information on the aging mechanism of HT9 was obtained, allowing for a more informed prediction, and understanding of the long-term behavior, performance and thermal stability of ferritic-martensitic alloys exposed to elevated temperatures.
{"title":"Long-term thermal aging effects in ferritic-martensitic steel HT9","authors":"D.J. Sprouster , B. Adam , A. Koziol , L. Rolly , C. Huotilainen , J.D. Tucker","doi":"10.1016/j.matchar.2024.114418","DOIUrl":"10.1016/j.matchar.2024.114418","url":null,"abstract":"<div><div>The ferritic-martensitic steel HT9 is a candidate material for fuel cladding and core components in advanced nuclear reactors, such as sodium-cooled fast reactors, thanks to their high temperature mechanical properties and low susceptibility to irradiation induced swelling phenomena. However, thermal stability and elevated temperature microstructural evolution in these alloys may impact their long-term behavior and reliability. In this work, the effects of thermal aging on the microstructural and mechanical properties of HT9 have been investigated through complementary electron microscopy, synchrotron X-ray diffraction, microhardness, and thermodynamic modeling. Plates of HT9 were aged up to 50 kh at relevant sodium-cooled fast reactor operational temperatures (360 °C - 700 °C). Trends in microstructure as a function of aging time and temperature were apparent from qualitative and quantitative analysis. These observations were further supported by thermodynamic modeling of the bulk and precipitate phases. Specific phases observed include BCC Fe, FCC M<sub>23</sub>C<sub>6</sub>, HCP and FCC MX phase and Laves M<sub>2</sub>X phase. Through the application of our multi-scale and multi-modal approach, clear information on the aging mechanism of HT9 was obtained, allowing for a more informed prediction, and understanding of the long-term behavior, performance and thermal stability of ferritic-martensitic alloys exposed to elevated temperatures.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114418"},"PeriodicalIF":4.8,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-29DOI: 10.1016/j.matchar.2024.114411
Nan Jiang , Hong Bian , Xiaoguo Song , Hyoung Seop Kim , Danyang Lin , Weimin Long , Sujuan Zhong , Lianhui Jia , Daijun Hu
In this paper, the Zr53Cu47 (wt%) alloys were designed by vacuum melting for the joining Zirconium (Zr) alloys to equiatomic CoCrFeMnNi high entropy alloys (HEA). The wetting, microstructure, growth kinetics of reaction layer, shear strength and rupture behavior of joints evolved with temperature were specifically deliberated. The interfacial reactions were determined to be CrMn layer/Zr(Cr,Mn)2 layer + corpuscular β-Zr/tuberous Zr2(Cu,Ni,Co,Fe) + Zrss + tuberous Zr(Cr,Mn)2 from HEA to Zr-3. Herein, the β-Zr precipitates with the sterling plasticity had the semi-coherent relationship with the matrix phase Zr(Cr,Mn)2, and β-Zr precipitates developed with the elevated temperature, contributing to the plasticity improvement of Zr(Cr,Mn)2 and the growth of joints properties. The activation energy (Q) of CrMn was 127.0 kJ/mol, significantly less than that that of Zr(Cr,Mn)2 (159.7 kJ/mol), thereby the generation of CrMn was underlying to Zr(Cr,Mn)2 during brazing. Moreover, grains orientations in CrMn and Zr(Cr,Mn)2 were stochastically dispersed. The strength of Zr-3/Zr53Cu47/HEA achieved peak of 136.8 MPa when brazed at 970 °C/10 min. Cracks were preferably started at the non-coherent interface of Zr(Cr,Mn)2/CrMn with the higher lattice mismatch degree of 26.0 % in I area, and propagated toward tuberous Zr2(Cu,Ni,Co,Fe) in II area.
{"title":"Microstructure and mechanical property of Zr-3/CoCrFeMnNi high-entropy alloys joints brazed using a novel ZrCu alloys","authors":"Nan Jiang , Hong Bian , Xiaoguo Song , Hyoung Seop Kim , Danyang Lin , Weimin Long , Sujuan Zhong , Lianhui Jia , Daijun Hu","doi":"10.1016/j.matchar.2024.114411","DOIUrl":"10.1016/j.matchar.2024.114411","url":null,"abstract":"<div><div>In this paper, the Zr53Cu47 (wt%) alloys were designed by vacuum melting for the joining Zirconium (Zr) alloys to equiatomic CoCrFeMnNi high entropy alloys (HEA). The wetting, microstructure, growth kinetics of reaction layer, shear strength and rupture behavior of joints evolved with temperature were specifically deliberated. The interfacial reactions were determined to be CrMn layer/Zr(Cr,Mn)<sub>2</sub> layer + corpuscular β-Zr/tuberous Zr<sub>2</sub>(Cu,Ni,Co,Fe) + Zrss + tuberous Zr(Cr,Mn)<sub>2</sub> from HEA to Zr-3. Herein, the β-Zr precipitates with the sterling plasticity had the semi-coherent relationship with the matrix phase Zr(Cr,Mn)<sub>2</sub>, and β-Zr precipitates developed with the elevated temperature, contributing to the plasticity improvement of Zr(Cr,Mn)<sub>2</sub> and the growth of joints properties. The activation energy (Q) of CrMn was 127.0 kJ/mol, significantly less than that that of Zr(Cr,Mn)<sub>2</sub> (159.7 kJ/mol), thereby the generation of CrMn was underlying to Zr(Cr,Mn)<sub>2</sub> during brazing. Moreover, grains orientations in CrMn and Zr(Cr,Mn)<sub>2</sub> were stochastically dispersed. The strength of Zr-3/Zr53Cu47/HEA achieved peak of 136.8 MPa when brazed at 970 °C/10 min. Cracks were preferably started at the non-coherent interface of Zr(Cr,Mn)<sub>2</sub>/CrMn with the higher lattice mismatch degree of 26.0 % in I area, and propagated toward tuberous Zr<sub>2</sub>(Cu,Ni,Co,Fe) in II area.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114411"},"PeriodicalIF":4.8,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418221","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 : 2024-09-27DOI: 10.1016/j.matchar.2024.114414
Ran Bi , Jing Li , Decheng Wang , Zhou Zhou , Jingxian Ma , Tielong Shen , Shanchao Zuo , Minghuan Cui , Lilong Pang , Peng Jin
Fe-based amorphous coatings exhibit exceptional irradiation resistance attributed to their distinct topologically disordered structure, rendering them highly attractive for advanced nuclear energy applications. The incorporation of WB secondary phase doping can notably alter the coating to enhance its operational safety. In this investigation, three different Fe-based composite coatings, with varying WB doping levels of 5 %, 10 %, and 15 % were fabricated through the High-Velocity Oxy-Fuel (HVOF) spraying technique. Irradiation tests were conducted at room temperature utilizing a proton beam with an energy of 1.52 MeV to simulate neutron irradiation environment in a nuclear reactor. The microstructure evolution before and after irradiation was systematically investigated with XRD, SEM, and TEM techniques. The results demonstrated that proton irradiation induced free volume, crystallization and H bubbles evolution. The doping of WB diminished the proton implantation dose threshold for segregation in irradiation plateaus while enhancing the growth of precipitates around the damage zone by inducing the production of M23C6 carbides and, at the same time, increasing the probability of H bubble nucleation and growth. These findings provide insights for iterative updates in Fe-based amorphous materials, informing their further development and application.
铁基无定形涂层因其独特的拓扑无序结构而表现出卓越的耐辐照性能，使其在先进核能应用中具有极高的吸引力。加入 WB 二相掺杂可以显著改变涂层，从而提高其运行安全性。在这项研究中，通过高速富氧燃料（HVOF）喷涂技术制造了三种不同的铁基复合涂层，其 WB 掺杂水平分别为 5%、10% 和 15%。利用能量为 1.52 MeV 的质子束在室温下进行了辐照试验，以模拟核反应堆中的中子辐照环境。利用 XRD、SEM 和 TEM 技术对辐照前后的微观结构演变进行了系统研究。结果表明，质子辐照诱导了自由体积、结晶和 H 气泡的演化。WB 的掺杂降低了辐照高原偏析的质子植入剂量阈值，同时通过诱导 M23C6 碳化物的产生，促进了损伤区周围沉淀物的生长，同时增加了 H 气泡成核和生长的概率。这些发现为铁基非晶材料的迭代更新提供了启示，为其进一步开发和应用提供了参考。
{"title":"Microstructure evolution mechanism of WB-doped Fe-based amorphous composite coating under proton beam irradiation","authors":"Ran Bi , Jing Li , Decheng Wang , Zhou Zhou , Jingxian Ma , Tielong Shen , Shanchao Zuo , Minghuan Cui , Lilong Pang , Peng Jin","doi":"10.1016/j.matchar.2024.114414","DOIUrl":"10.1016/j.matchar.2024.114414","url":null,"abstract":"<div><div>Fe-based amorphous coatings exhibit exceptional irradiation resistance attributed to their distinct topologically disordered structure, rendering them highly attractive for advanced nuclear energy applications. The incorporation of WB secondary phase doping can notably alter the coating to enhance its operational safety. In this investigation, three different Fe-based composite coatings, with varying WB doping levels of 5 %, 10 %, and 15 % were fabricated through the High-Velocity Oxy-Fuel (HVOF) spraying technique. Irradiation tests were conducted at room temperature utilizing a proton beam with an energy of 1.52 MeV to simulate neutron irradiation environment in a nuclear reactor. The microstructure evolution before and after irradiation was systematically investigated with XRD, SEM, and TEM techniques. The results demonstrated that proton irradiation induced free volume, crystallization and H bubbles evolution. The doping of WB diminished the proton implantation dose threshold for segregation in irradiation plateaus while enhancing the growth of precipitates around the damage zone by inducing the production of M<sub>23</sub>C<sub>6</sub> carbides and, at the same time, increasing the probability of H bubble nucleation and growth. These findings provide insights for iterative updates in Fe-based amorphous materials, informing their further development and application.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114414"},"PeriodicalIF":4.8,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418167","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 : 2024-09-27DOI: 10.1016/j.matchar.2024.114400
Wang An , Zhi-he Dou , Ting-an Zhang , Jin-ru Han
To address the problems of low performance and density in CuCr50 alloys prepared by aluminum thermal reduction-electromagnetic casting, a synergistic process involving hot forging deformation to eliminate micropores in the alloy and heat treatment to modify the alloy was proposed. The effect of hot forging temperature on the microstructure evolution and performance strengthening of CuCr50 alloys during heat treatment was studied. The results show that the properties of CuCr50 alloys forged at different temperatures after heat treatment are better than those after direct heat treatment. After heat treatment, the conductivity of CuCr50 alloys forged at 800 °C reaches 22.41 MS/m, the density reaches 7.94 g/cm3, and the hardness reaches 112 HB, which are 73.59 %, 4.75 % and 37.59 % greater than those of the as-cast alloy, respectively. The microstructure analysis showed that the nano-Cr phase precipitated during the aging process of CuCr50 alloys after hot forging at 750 °C–850 °C had a semi-coherent relationship with the Cu matrix, which played a role in coherent strengthening. After hot forging at 900 °C, the precipitated Cr phase has an incoherent relationship with the Cu matrix, which played a role of dispersion strengthening. The performance test of 40.5 kV simulated vacuum interrupter shows that the breaking and chopping performance of the prepared CuCr50 contact material is obviously better than that of commercial products, which is expected to become a new process for the preparation of high performance CuCr contact materials.
{"title":"Microstructure and property evolution of CuCr50 alloy prepared by aluminum thermal reduction-electromagnetic casting during hot forging process","authors":"Wang An , Zhi-he Dou , Ting-an Zhang , Jin-ru Han","doi":"10.1016/j.matchar.2024.114400","DOIUrl":"10.1016/j.matchar.2024.114400","url":null,"abstract":"<div><div>To address the problems of low performance and density in CuCr50 alloys prepared by aluminum thermal reduction-electromagnetic casting, a synergistic process involving hot forging deformation to eliminate micropores in the alloy and heat treatment to modify the alloy was proposed. The effect of hot forging temperature on the microstructure evolution and performance strengthening of CuCr50 alloys during heat treatment was studied. The results show that the properties of CuCr50 alloys forged at different temperatures after heat treatment are better than those after direct heat treatment. After heat treatment, the conductivity of CuCr50 alloys forged at 800 °C reaches 22.41 MS/m, the density reaches 7.94 g/cm<sup>3</sup>, and the hardness reaches 112 HB, which are 73.59 %, 4.75 % and 37.59 % greater than those of the as-cast alloy, respectively. The microstructure analysis showed that the nano-Cr phase precipitated during the aging process of CuCr50 alloys after hot forging at 750 °C–850 °C had a semi-coherent relationship with the Cu matrix, which played a role in coherent strengthening. After hot forging at 900 °C, the precipitated Cr phase has an incoherent relationship with the Cu matrix, which played a role of dispersion strengthening. The performance test of 40.5 kV simulated vacuum interrupter shows that the breaking and chopping performance of the prepared CuCr50 contact material is obviously better than that of commercial products, which is expected to become a new process for the preparation of high performance CuCr contact materials.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114400"},"PeriodicalIF":4.8,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418175","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 : 2024-09-27DOI: 10.1016/j.matchar.2024.114415
Yuanhang Chen, Chunli Yang
Directed energy deposition-arc (DED-arc) additive manufacturing technology was used to repair the damaged 718Plus components. This work shows that TiC/Cr2C3 addition to 718Plus alloy is an effective way to suppress the formation of the unfavorable Laves phase. TiC additions to 718Plus alloy can alleviate the elemental segregation, refine the dendritic structure and promote the formation of blocky TiC-NbC core-shell carbides and NbC carbides, while Cr2C3 additions enable the precipitation of rod-like NbC carbides. During the deposition process, the TiC/Cr2C3 additions were dissolved into the molten pool and decomposed into Ti, Cr, and C. The introduction of additional carbon in the melt drastically consumed the Nb available for Laves phase. The tensile tests show that TiC addition to 718Plus alloy contributed to an increased tensile strength of about 120 MPa due to the reduced amount of Laves phase and the reinforced effect of carbides. The fracture behaviour of carbides was explained in detail. The critical shear stress for blocky carbides to crack is higher than that required for rod-like ones, suggesting that TiC additions were desirable for better ductility compared with Cr2C3 additions.
{"title":"Laves phase control and tensile properties optimization of DED-arc repaired 718Plus components through the addition of TiC and Cr2C3","authors":"Yuanhang Chen, Chunli Yang","doi":"10.1016/j.matchar.2024.114415","DOIUrl":"10.1016/j.matchar.2024.114415","url":null,"abstract":"<div><div>Directed energy deposition-arc (DED-arc) additive manufacturing technology was used to repair the damaged 718Plus components. This work shows that TiC/Cr<sub>2</sub>C<sub>3</sub> addition to 718Plus alloy is an effective way to suppress the formation of the unfavorable Laves phase. TiC additions to 718Plus alloy can alleviate the elemental segregation, refine the dendritic structure and promote the formation of blocky TiC-NbC core-shell carbides and NbC carbides, while Cr<sub>2</sub>C<sub>3</sub> additions enable the precipitation of rod-like NbC carbides. During the deposition process, the TiC/Cr<sub>2</sub>C<sub>3</sub> additions were dissolved into the molten pool and decomposed into Ti, Cr, and C. The introduction of additional carbon in the melt drastically consumed the Nb available for Laves phase. The tensile tests show that TiC addition to 718Plus alloy contributed to an increased tensile strength of about 120 MPa due to the reduced amount of Laves phase and the reinforced effect of carbides. The fracture behaviour of carbides was explained in detail. The critical shear stress for blocky carbides to crack is higher than that required for rod-like ones, suggesting that TiC additions were desirable for better ductility compared with Cr<sub>2</sub>C<sub>3</sub> additions.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114415"},"PeriodicalIF":4.8,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418169","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 : 2024-09-25DOI: 10.1016/j.matchar.2024.114413
Yong Hee Jo , Hyung-Jun Cho , Junha Yang , Sukjin Lee
Ensuring toughness in thick hot-rolled plates remains a challenge for lightweight steels in automotive, shipbuilding, military, and construction industries despite improved tensile properties. This study investigated the Charpy absorbed energy of thick hot-rolled Fe-0.4C-15Mn-6Al duplex lightweight steel plates exhibiting TRIP and TWIP mechanisms, aged at 450–500 °C to precipitate κ-carbides. Fracture initiation and propagation energies measured from instrumented Charpy impact testing were analyzed through microstructural and microfracture analyses. The 500 °C-aged (A500) specimen showed the highest Charpy absorbed energy, composed of the highest fracture initiation and propagation energies across all test temperatures, particularly due to active TWIP and TRIP mechanisms along with significant κ-carbide precipitation strengthening. Despite predominantly ductile fracture modes, regardless of aging temperature and test temperature, deformation mechanisms were influenced by stacking fault energy (SFE). Aging resulted in κ-carbide precipitation, reducing C and Mn contents in austenite and lowering SFE. At 25 °C, the superior energy absorption of the A500 specimen (296 J) was attributed to its high flow stress and extensive roughness in the fracture surface due to crack deflection in the fracture initiation region and zigzag crack propagation. The Charpy absorbed energy decreased significantly at lower temperatures due to limited development of slip line field and less zigzag crack propagation. Despite this, the A500 specimen maintained the highest energy absorption due to its optimized TWIP and TRIP mechanisms and κ-carbide precipitation strengthening.
{"title":"Enhancing charpy absorbed energy of aged duplex lightweight steel plates through TRIP and TWIP mechanisms","authors":"Yong Hee Jo , Hyung-Jun Cho , Junha Yang , Sukjin Lee","doi":"10.1016/j.matchar.2024.114413","DOIUrl":"10.1016/j.matchar.2024.114413","url":null,"abstract":"<div><div>Ensuring toughness in thick hot-rolled plates remains a challenge for lightweight steels in automotive, shipbuilding, military, and construction industries despite improved tensile properties. This study investigated the Charpy absorbed energy of thick hot-rolled Fe-0.4C-15Mn-6Al duplex lightweight steel plates exhibiting TRIP and TWIP mechanisms, aged at 450–500 °C to precipitate κ-carbides. Fracture initiation and propagation energies measured from instrumented Charpy impact testing were analyzed through microstructural and microfracture analyses. The 500 °C-aged (A500) specimen showed the highest Charpy absorbed energy, composed of the highest fracture initiation and propagation energies across all test temperatures, particularly due to active TWIP and TRIP mechanisms along with significant κ-carbide precipitation strengthening. Despite predominantly ductile fracture modes, regardless of aging temperature and test temperature, deformation mechanisms were influenced by stacking fault energy (SFE). Aging resulted in κ-carbide precipitation, reducing C and Mn contents in austenite and lowering SFE. At 25 °C, the superior energy absorption of the A500 specimen (296 J) was attributed to its high flow stress and extensive roughness in the fracture surface due to crack deflection in the fracture initiation region and zigzag crack propagation. The Charpy absorbed energy decreased significantly at lower temperatures due to limited development of slip line field and less zigzag crack propagation. Despite this, the A500 specimen maintained the highest energy absorption due to its optimized TWIP and TRIP mechanisms and κ-carbide precipitation strengthening.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114413"},"PeriodicalIF":4.8,"publicationDate":"2024-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328059","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 : 2024-09-24DOI: 10.1016/j.matchar.2024.114410
S. Xu , J. Pons , R. Santamarta
The paper reports on the functional properties and microstructure of polycrystalline Ni-Mn-Ga-Hf high temperature shape memory alloys, in which different amounts of Hf up to 4 at.% are added in substitution of Mn and Ga, while the nominal Ni content is kept constant. The increase in the amount of Hf promotes a decrease in the valence electron concentration (e/a), tetragonality (c/a) of the martensitic unit cell, and martensitic transformation temperatures, as well as a significant decrease of the transformation hysteresis. The non-modulated tetragonal martensite, typical of Ni-Mn-Ga high temperature shape memory alloys, is formed in all the alloys studied here, though the alloy with 4 at.% of Hf also contains a small fraction of modulated 14M martensite. Hf addition improves the thermomechanical response of the alloys under compressive stress up to 300 MPa and leads to nearly closed cycles with minimal irrecoverable strain and low hysteresis (8 K) for the alloys with 3 and 4 at.% of Hf. These alloys also demonstrate excellent stability under repetitive thermal cycling and little change upon aging at 870 K. A second phase rich in Hf and Ni starts to precipitate at 1 at.% of Hf addition and its volume fraction experiences an abrupt and progressive increase for higher Hf contents. The structure of the second phase looks like the usual f.c.c. γ phase reported in other Ni-Mn-Ga-based alloys, but it has a double lattice parameter. Two structural models based on the A6 face-centered tetragonal unit cell with space group I4/mmm (No. 139), equivalent to the double f.c.c. lattice, are proposed for this new phase.
{"title":"Impact of Hf alloying on the functional properties of Ni-Mn-Ga high temperature shape memory alloys","authors":"S. Xu , J. Pons , R. Santamarta","doi":"10.1016/j.matchar.2024.114410","DOIUrl":"10.1016/j.matchar.2024.114410","url":null,"abstract":"<div><div>The paper reports on the functional properties and microstructure of polycrystalline Ni-Mn-Ga-Hf high temperature shape memory alloys, in which different amounts of Hf up to 4 at.% are added in substitution of Mn and Ga, while the nominal Ni content is kept constant. The increase in the amount of Hf promotes a decrease in the valence electron concentration (<em>e</em>/<em>a</em>), tetragonality (<em>c</em>/<em>a</em>) of the martensitic unit cell, and martensitic transformation temperatures, as well as a significant decrease of the transformation hysteresis. The non-modulated tetragonal martensite, typical of Ni-Mn-Ga high temperature shape memory alloys, is formed in all the alloys studied here, though the alloy with 4 at.% of Hf also contains a small fraction of modulated 14M martensite. Hf addition improves the thermomechanical response of the alloys under compressive stress up to 300 MPa and leads to nearly closed cycles with minimal irrecoverable strain and low hysteresis (8 K) for the alloys with 3 and 4 at.% of Hf. These alloys also demonstrate excellent stability under repetitive thermal cycling and little change upon aging at 870 K. A second phase rich in Hf and Ni starts to precipitate at 1 at.% of Hf addition and its volume fraction experiences an abrupt and progressive increase for higher Hf contents. The structure of the second phase looks like the usual f.c.c. γ phase reported in other Ni-Mn-Ga-based alloys, but it has a double lattice parameter. Two structural models based on the A6 face-centered tetragonal unit cell with space group I4/mmm (No. 139), equivalent to the double f.c.c. lattice, are proposed for this new phase.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"217 ","pages":"Article 114410"},"PeriodicalIF":4.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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