Materials Characterization最新文献

Investigation of microstructure, mechanical performance, and corrosion resistance of thin-walled titanium welded pipe by annealing process 热处理薄壁钛焊管的组织、力学性能和耐蚀性研究

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114579

Jibing Chen , Yanfeng Liu , Qi Chen , Zhixiong Xie

Thin-wall titanium welded pipe has important applications in the fields of new energy vehicles, aerospace, and heat exchangers, the mechanical properties and corrosion resistance after high-frequency induction welding are rarely studied. To improve the comprehensive performance of thin-walled titanium welded pipe, a heat process and the performance optimization mechanism were studied in this paper. In addition, we systematically explored the influence of heat treatment conditions on the microstructure, mechanical performance, and dissolution behavior of the welded pipe through various methods, including tensile tests, immersion tests, and electrochemical tests. The results indicated that heat treatment primarily regulates the quantity and distribution of martensitic phases, acicular structures, and serrated structures in the welded joints, thereby impacting the mechanical performance of the welded pipe. By following high-temperature annealing at 800 °C for 0.5 h, with a heating rate of 5 °C/min, the acicular and serrated structures in the welded joints completely disappeared, forming an annealed equiaxed structure consistent with the base material. Subsequent furnace cooling reduced internal thermal stresses within the grains, resulting in relatively smooth grain boundaries, reduced small-sized grains, and a more uniform distribution of grain sizes, ultimately eliminating the residual stresses. Consequently, the welded pipe exhibited outstanding comprehensive performance, including ultimate tensile strength, Vickers hardness, and fracture elongation of 439.2 MPa, 178.3 HV, and 18 %, respectively. Notably, under room temperature, after immersion in a 3.5 % sodium chloride solution for 28 days, there was no significant change in the sample's mass. Therefore, the properties of thin-walled titanium welded pipe can be improved by annealing process, and it provides strong support and reliable evidence for its application in related fields.

薄壁钛焊管在新能源汽车、航空航天、换热器等领域有重要应用，高频感应焊接后的力学性能和耐腐蚀性能研究较少。为提高薄壁钛焊管的综合性能，研究了薄壁钛焊管的加热工艺及其性能优化机理。此外，通过拉伸试验、浸没试验、电化学试验等多种方法，系统探讨了热处理条件对焊管组织、力学性能和溶解行为的影响。结果表明：热处理主要调节焊接接头中马氏体相、针状组织和锯齿状组织的数量和分布，从而影响焊管的力学性能；在800℃高温退火0.5 h，升温速度5℃/min后，焊接接头中的针状和锯齿状组织完全消失，形成与母材一致的退火等轴组织。随后的炉内冷却降低了晶粒内部的热应力，使得晶界相对光滑，小晶粒减少，晶粒尺寸分布更加均匀，最终消除了残余应力。结果表明，焊管的抗拉强度、维氏硬度和断裂伸长率分别达到439.2 MPa、178.3 HV和18%，综合性能优异。值得注意的是，在室温下，在3.5%氯化钠溶液中浸泡28天后，样品的质量没有明显变化。因此，通过退火工艺可以改善薄壁钛焊管的性能，为其在相关领域的应用提供了强有力的支持和可靠的证据。

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引用次数: 0

Simultaneous enhancement of the strength and plasticity of Fe12Mn steel through modulating grain morphology 通过调节晶粒形貌来同时提高Fe12Mn钢的强度和塑性

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114566

Tao Li , Zhiqiang Wu , Wei Liu , Hui Liu , Nan Tang , Haijun Pan , Zhihui Cai , Jun Hu

The relationship between grain morphology and tensile properties of Fe-12Mn steel thermo-mechanically processed by rolling annealing and re-cold rolling processes was investigated. The results indicated that the re-cold rolling deformed the mostly austenite grain morphology from equiaxed to lamellar, and the steel exhibited a yield strength of 1295 MPa, tensile strength of 1518 MPa, and elongation of 18 %. Compared to the experimental steel without re-cold rolling processes, more than 300 MPa tensile strength was improved and elongation increased from 14 % to 18 %. The steel demonstrated remarkable enhancement in mechanical properties owing to the “multistage TRIP effect”, which referred to the sequential martensitic phase transformation of austenite with varying stability as the strain increased. The change in grain morphology reduced the rate of twin formation and increased the nucleation point of the martensitic phase transition, this also stabilized the retained austenite by increasing the hard phases surrounding the retained austenite, which had multistage stability. These factors contributed to the “multistage TRIP effect”, which could be sustained to higher strains and presented regular fluctuations in work-hardening rates

研究了Fe-12Mn钢经轧制退火和再冷轧热处理后晶粒形貌与拉伸性能的关系。结果表明：经再冷轧后，钢的屈服强度为1295 MPa，抗拉强度为1518 MPa，伸长率为18%；与未进行再冷轧的试验钢相比，抗拉强度提高了300mpa以上，伸长率从14%提高到18%。由于“多级TRIP效应”，该钢的力学性能得到了显著提高，这是指随着应变的增加，奥氏体的顺序马氏体相变具有不同的稳定性。晶粒形貌的改变降低了孪晶的形成速度，增加了马氏体相变的形核点，也通过增加残余奥氏体周围的硬相来稳定残余奥氏体，具有多阶段稳定性。这些因素导致了“多级TRIP效应”，这种效应可以持续到更高的应变，并呈现出加工硬化速率的规律波动

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引用次数: 0

Liquation cracking facilitated by stray-grain chains in a high-γ'-content nickel-based alloy K4002 produced via electron beam powder bed fusion 电子束粉末床熔合制备的高γ′含量镍基合金K4002中杂散晶链的溶解开裂

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114589

Yunting Li , Maodong Kang , Yang Zhou , Yuantao Xu , Huipeng Yu , Yufei Pan , Jun Wang , Chengqi Zhang

Cracking significantly hinders the development of additive manufactured high-γ’-content nickel-based alloys. This study investigates the microstructure and cracking behavior of a high-γ'-content nickel-based alloy K4002 produced via electron beam powder bed fusion (EBPBF). The results suggest that liquation cracking is the predominant cracking mechanism observed. Stray-grain chains were found to promote liquation cracking due to several factors: i) The presence of high angle grain boundaries (HAGBs) between the stray grains and adjacent columnar grains; ii) the higher density of geometrically necessary dislocations (GND) within stray grains; iii) Cr₂₃C₆ carbides, at the stray grain boundaries, hinder dislocation motion and promote strain accumulation; and iv) the formation of low-melting-point regions around the Cr₂₃C₆ within the stray grain chains. Furthermore, the origin of stray-grain chains was analyzed using the Rayleigh number and the columnar-to-equiaxed transition (CET) criterion, revealing that the stray-grain chains originate from the CET. As a result, through optimizing the solidification rate to inhibit CET, stray-grain chains were effectively eliminated, leading to a 55 % reduction in crack incidence. The findings in this work provide guidance for mitigating liquation cracking induced by stray-grain chains during additive manufacturing.

裂纹严重阻碍了增材制造高γ′含量镍基合金的发展。研究了采用电子束粉末床熔合法制备的高γ′含量镍基合金K4002的显微组织和开裂行为。结果表明，液化开裂是主要的开裂机制。发现散失晶粒链促进液化开裂的原因有以下几个：1)散失晶粒与相邻柱状晶粒之间存在高角晶界（HAGBs）；ii)杂散颗粒中几何必要位错（GND）的密度更高；iii) Cr23C6碳化物在杂散晶界处阻碍位错运动，促进应变积累；杂散晶粒链中Cr23C6周围形成低熔点区域。此外，利用瑞利数和柱向等轴转变（CET）准则分析了散粒链的起源，揭示了散粒链起源于CET。结果表明，通过优化凝固速率抑制固相损伤，有效地消除了散晶链，使裂纹发生率降低了55%。本工作的发现为减轻增材制造过程中由散粒链引起的液化开裂提供了指导。

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引用次数: 0

On the dislocation storage capacity of additively manufactured Hastelloy X: In situ synchrotron diffraction study 增材制造哈氏合金X的位错储存能力：原位同步加速器衍射研究

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114573

Kartik Prasad , Atsushi Ito , Shiro Torizuka

Considering the results obtained from different types of synchrotron diffraction experiments, this research investigation presents deeper insights about the effects of heat treatment on characterization of microstructure and mechanical properties of laser powder bed fusion (L-PBF) processed Hastelloy X (HX). HX is a candidate material for variety of applications ranging from petroleum and chemical industries, high temperature gas cooled reactors and gas turbine engines. L-PBF processed samples of HX were subjected to three aging treatments at 650 °C, 760 °C and 870 °C after solutionizing them at 1175 °C. Examination of Debye-Scherrer rings and orientation imaging maps (OIM) of electron back scattered diffraction (EBSD) experiments revealed the randomization of grains in heat treated microstructures of HX. Synchrotron diffraction patterns and transmission electron microscopy observations confirmed the presence of laves phase and carbides (M₆C and M₂₃C₆) in as-built HX (AB-HX). Increase in precipitation of M₂₃C₆ carbides with increase in aging treatment from 650 °C to 870 °C was revealed by line profiles of synchrotron diffraction patterns and EBSD phase maps. Tensile deformation behavior in four different metallurgical conditions of HX viz. AB-HX, solution treated (ST), solution treated and aged conditions was characterized by evaluating the evolving dislocation density carrying out in situ synchrotron diffraction experiments. The diffraction data corresponding to the first six {hkl} reflections were considered for evaluating the dislocation density using modified Warren-Averback methodology. Analysis of work hardening behavior, as probed by dislocation density measurements, indicated increase in dislocation storage capacity with increase in aging treatment from 650 °C to 870 °C. Variations in tensile properties were analyzed in light of the dislocation density measurements and EBSD results to gain more insight into the deformation mechanisms operating in different heat-treated conditions.

结合不同类型同步加速器衍射实验的结果，本研究深入探讨了热处理对激光粉末床熔合（L-PBF）加工哈氏合金X （HX）的显微组织和力学性能的影响。HX是石油和化学工业、高温气冷反应堆和燃气涡轮发动机等各种应用的候选材料。L-PBF处理的HX样品在1175℃固溶后，分别在650℃、760℃和870℃进行三次时效处理。Debye-Scherrer环和电子背散射衍射（EBSD）实验的取向成像图（OIM）揭示了HX热处理显微组织中晶粒的随机性。同步加速器衍射图和透射电镜观察证实，在构建的HX （AB-HX）中存在叶片相和碳化物（M6C和M23C6）。同步加速器衍射图和EBSD相图显示，在650 ~ 870℃时效处理期间，M23C6碳化物析出量随时效时间的增加而增加。通过原位同步衍射实验评价位错密度的变化，表征了HX在AB-HX、固溶处理（ST）、固溶处理和时效4种不同冶金条件下的拉伸变形行为。采用改进的Warren-Averback方法计算位错密度时，考虑了前六个{hkl}反射对应的衍射数据。通过位错密度测量对加工硬化行为的分析表明，从650°C到870°C，随着时效处理的增加，位错存储容量增加。根据位错密度测量和EBSD结果分析拉伸性能的变化，以更深入地了解不同热处理条件下的变形机制。

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引用次数: 0

Twin-twin interaction behavior in tensile-deformed austenitic manganese steel 拉伸变形奥氏体锰钢的孪晶相互作用行为

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114582

Linnan Dong , Zhimin Ding , Bo Liang , Qiaomei Huang , Rujin Tian

Electron back scatter diffraction instrument and high-resolution transmission electron microscope were used to observe and characterize the twin-twin interaction behavior in tensile-deformed 120Mn13 steel at the atomic scale. Here the whole twin-twin interaction behavior was divided into three processes and the deformation mechanisms of each process were revealed, including the interaction between the incident twin and the coherent twin boundary of the barrier twin, which can lead to a twinning or detwinning process of the barrier twin, the trigger formation of secondary twins and the formation of second order twins in the intersection region. Based on the Thomson tetrahedron, the dislocation movements in different twin-twin interaction processes were systematically described, and the possibility of dislocation reactions were discussed in energy. The interaction mechanism of the microscopic zero-stain twin (MZST) was proposed for the first time, and its differences from the classical twin-twin interaction mechanism were expounded. Present work further enriches the twin-twin interaction behavior in face centered cubic metallic materials. It can also guide the in-depth understanding of the classical twin-twin interaction behaviors and be used to explain the formation of classical secondary and second order twins.

采用电子背散射衍射仪和高分辨率透射电镜在原子尺度上观察和表征了拉伸变形120Mn13钢的孪晶相互作用行为。本文将整个孪晶相互作用行为分为三个过程，并揭示了每个过程的变形机制，包括入射孪晶与势垒孪晶的相干孪晶边界之间的相互作用，这种相互作用可导致势垒孪晶的孪生或脱孪生过程，触发二级孪晶的形成以及在相交区域形成二级孪晶。基于汤姆逊四面体，系统地描述了不同孪晶相互作用过程中的位错运动，并从能量上讨论了位错反应的可能性。首次提出了微观零污点孪晶（MZST）的相互作用机理，并阐述了其与经典孪晶相互作用机理的区别。本工作进一步丰富了面心立方金属材料的孪晶相互作用行为。它还可以指导对经典双胞胎相互作用行为的深入理解，并用于解释经典二级和二级双胞胎的形成。

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引用次数: 0

Ex-situ observation of ferrite grain growth behavior in a welded 9Cr-1Mo-V-Nb steel during aging at 740 °C 焊接9Cr-1Mo-V-Nb钢740℃时效过程中铁素体晶粒生长行为的原位观察

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114584

Katsuhiro Sato , Masatoshi Mitsuhara , Akihiro Shin , Yoshiki Shioda , Kyohei Nomura , Keiji Kubushiro , Noriko Saito , Hideharu Nakashima

It has recently been reported that ferrite grains coarsened to several hundred micrometers were occasionally observed in long-term serviced 9Cr-1Mo-V-Nb steel welds. To clarify the factors that cause ferrite grain growth in martensite during high-temperature exposure, alternating aging heat treatment and observation of the same field of view was performed using a welded 9Cr-1Mo-V-Nb steel. Such ex-situ observations revealed that the rapid grain growth of ferrite by consuming martensite occurred in the weld metal during aging at 740 °C. In the test material used in this study, some δ-ferrite grains were observed in the weld metal near the fusion line. In the region where δ-ferrite grains were observed, the concentrations of austenite-forming elements such as Mn and Ni were locally decreased in the matrix due to dilution by the base metal, promoting δ-ferrite retention after welding. Ex-situ observation indicated that no significant grain growth of δ-ferrite occurred during aging. Therefore, it was suggested that a new ferrite grain formation followed by rapid grain growth consuming martensite occurred during aging. The elastic strain energy density of the dislocations P^M_dis and the interfacial energy density P^M_surf in martensite can affect the driving force for ferrite grain growth by consuming martensite. Based on the evaluation results for P^M_dis and P^M_surf after 500 h of aging, P^M_surf was considered to be the main driving force for ferrite grain growth. Although the ferrite-formation process could not be directly observed, it is possible that ferrite was formed by the recrystallization of martensite through the bulging mechanism.

最近有报道称，在长期服务的9Cr-1Mo-V-Nb钢焊缝中偶尔会观察到粗化到几百微米的铁素体晶粒。为了弄清高温暴露导致马氏体中铁素体晶粒生长的因素，采用9Cr-1Mo-V-Nb焊接钢进行了交替时效热处理和相同视场观察。这种非原位观察表明，在740℃时效过程中，焊缝金属中铁素体通过消耗马氏体而快速长大。在本研究使用的试验材料中，在熔合线附近的焊缝金属中观察到一些δ-铁素体晶粒。在观察到δ铁素体晶粒的区域，由于母材的稀释，基体中形成奥氏体的元素Mn和Ni的浓度在局部降低，促进了焊接后δ铁素体的保留。原位观察表明，时效过程中δ-铁素体晶粒未发生明显长大。因此，时效过程中出现了新的铁素体晶粒形成，随后晶粒快速长大，消耗马氏体。位错pmdi的弹性应变能密度和马氏体中的界面能密度可以通过消耗马氏体来影响铁素体晶粒长大的驱动力。时效500 h后对pmdi和PMsurf的评价结果表明，PMsurf是铁素体晶粒生长的主要驱动力。虽然不能直接观察到铁素体的形成过程，但有可能是马氏体通过胀形机制再结晶形成的铁素体。

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引用次数: 0

Microstructure and ablation resistance of C/C-HfC-SiC composites prepared by RMI with different powder particle sizes 不同粉末粒度RMI制备的C/C- hfc - sic复合材料的微观结构和抗烧蚀性能

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114577

Zhiqiang Liu, Yifan Sun, Shubo Zhang, Yawen Wang, Luncheng Tang, Tian Li, Qiangang Fu, Yujun Jia

To improve the ablation and scouring resistance of C/C composites, powder with particle sizes of 0.5–1 μm, 1–3 μm and 10–20 μm were used as infiltration powder to prepare C/C-HfC-SiC composites, named HSV-0.5-1, HSV-1-3 and HSV-10-20, respectively. Results show that the agglomeration of the powder makes it difficult to form a uniform and dense ceramic layer on the sample surface. The content of HfC ceramics increases with the particle size of the initial powder. In addition, the grain size of HfC first increases and then becomes irregularly spherical as the initial powder particle size increases. After ablation for 40s, HSV-1-3 shows the best resistance to ablation due to the mixed crystal form of flakes and spheres that form a denser oxide film in the center of the ablation. In three subsequent room-temperature airflow scour tests, the oxide film of HSV-1-3 and HSV-10-20 were damaged in the sample surface. After following ablation for 40 s, HSV-10-20 showed good ablation resistance with the linear ablation of −0.75 μm/s. The reason is the high HfC content and dense ceramic layer contribute to the formation of a continuous and complete oxide layer that prevents oxygen diffusion during ablation. This work provides guidance on the use of particle size in the RMI.

为提高C/C复合材料的抗烧蚀和耐冲刷性能，采用粒径为0.5-1 μm、1-3 μm和10-20 μm的粉末作为渗滤粉制备C/C- hfc - sic复合材料，分别命名为HSV-0.5-1、HSV-1-3和HSV-10-20。结果表明，粉末的团聚使样品表面难以形成均匀致密的陶瓷层。HfC陶瓷的含量随着初始粉体粒度的增大而增大。此外，随着初始粉体粒度的增大，HfC的晶粒尺寸先增大后呈不规则球形。烧蚀40s后，HSV-1-3的抗烧蚀性能最好，这是由于在烧蚀中心形成了更致密的氧化膜的片状和球形混合晶体形式。在随后的三次室温气流冲刷试验中，HSV-1-3和HSV-10-20的氧化膜在样品表面被破坏。烧蚀40 s后，HSV-10-20表现出良好的抗烧蚀性能，线性烧蚀速度为−0.75 μm/s。原因是高HfC含量和致密的陶瓷层有助于形成连续完整的氧化层，防止了烧蚀过程中氧气的扩散。这项工作为RMI中粒径的使用提供了指导。

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引用次数: 0

Effect of ball milling on densification and alloying in SiCp/Al powder metallurgy processes 球磨对SiCp/Al粉末冶金致密化和合金化的影响

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114583

X.M. Feng , J.F. Zhang , D. Wang , B. Deng , J. Wang , B.L. Xiao , Z.Y. Ma

In this study, unprocessed raw Al, Cu, Mg powders, and SiC particles were mixed and subjected to high-energy ball milling (HEBM) to mitigate the negative effects of the oxide film on the quality of the pressureless sintering billets. Comparative experiments including pores and intermetallics examination were performed on both the mixed and HEBM powders across various preparation stages, including cold isostatic pressing, sintering, and hot extrusion of the 15vol.%SiC/Al-Cu-Mg. The pore structure and degree of alloying were analyzed using X-ray synchrotron radiation tomography. The results indicate that the brief HEBM process led to excellent mechanical properties in aluminum matrix composites after pressureless sintering and hot extrusion. The composites using ball-milled powder was relatively denser and complete alloying after sintering and extrusion, resulting in a density of up to 0.995 and a uniform distribution of Cu elements. The HEBM SiCp/Al had a tensile strength of 573 MPa and a fracture strain of 5.1 % which were higher than that of the mixed SiCp/Al. The results indicate that diffusion of alloy elements such as Cu was hindered by the interfaces between powders, led to Cu segregation and lower density of only 0.982 even after extrusion. Therefore, the composites using mixed powder had a lower tensile strength of 483 MPa and a fracture strain of 3.5 %. The study concluded that reducing the number and types of inter-particle interfaces could enhance the alloying and pore bridging processes.

在本研究中，将未加工的Al， Cu， Mg粉末和SiC颗粒混合并进行高能球磨（HEBM），以减轻氧化膜对无压烧结坯料质量的负面影响。在15vol.%SiC/Al-Cu-Mg的不同制备阶段，包括冷等静压、烧结和热挤压，对混合粉末和HEBM粉末进行了孔隙和金属间化合物的比较实验。采用x射线同步辐射层析成像技术分析了合金的孔隙结构和合金化程度。结果表明：经过短时间的热挤压成形和无压烧结，铝基复合材料获得了优异的力学性能。采用球磨粉制备的复合材料经烧结和挤压后合金化程度较高，合金密度可达0.995，Cu元素分布均匀。HEBM SiCp/Al的拉伸强度为573 MPa，断裂应变为5.1%，高于混合SiCp/Al。结果表明：粉末间的界面阻碍了Cu等合金元素的扩散，导致Cu偏析，挤压后密度仅为0.982；因此，复合材料的抗拉强度为483 MPa，断裂应变为3.5%。研究表明，减少颗粒间界面的数量和类型可以促进合金化和孔桥接过程。

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引用次数: 0

Enhanced ultra-high temperature creep resistance originating from preferred microstructures of W-Re-HfC alloys W-Re-HfC合金的择优组织增强了其抗超高温蠕变性能

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114585

Shuai Ma , Di Dong , Mengyao Zhang , Ye Gao , Zhuangzhi Wu , Dezhi Wang

W-Re-HfC alloys have been extensively applied in the field of high-temperature structural parts. To ensure high temperature reliability, it is essential to enhance creep resistance ability. In this study, the microstructures of forged W-Re-HfC alloys were adjusted using different heat treatment processes. The corresponding tensile creep properties were also measured at 2000 °C with 40 MPa. Furthermore, a possible creep fracture mechanism was also explored. The forged W-Re-HfC sample annealed for 2 h exhibited the best creep performances with a steady-state creep rate of 3.28 × 10⁻⁶ and a creep life of 5.6 h. Generally, a larger grain size indicates a lower steady-state creep rate; however, the precipitation of carbides at the grain boundaries (GBs) deteriorates the bonding strength of interfaces, thus reversing the former trend. The dominant creep mechanism is diffusion creep, in which the voids nucleate perpendicular to the GBs, grow and connect into cracks, ultimately leading to fractures.

W-Re-HfC合金在高温结构件领域得到了广泛应用。为了保证高温可靠性，必须提高抗蠕变能力。在本研究中，采用不同的热处理工艺对锻造W-Re-HfC合金的组织进行了调整。在2000℃、40 MPa条件下，测定了相应的拉伸蠕变性能。此外，还探讨了可能的蠕变断裂机制。锻造后的W-Re-HfC试样退火2 h后蠕变性能最佳，稳态蠕变速率为3.28 × 10−6，蠕变寿命为5.6 h。然而，晶界处碳化物的析出使界面的结合强度下降，从而逆转了先前的趋势。蠕变的主要机制是扩散蠕变，在扩散蠕变中，空洞垂直于GBs形核，扩展并连接成裂纹，最终导致断裂。

引用次数: 0

In-situ TEM study on the precipitation behavior of an Al-Mn-Mg-Sc-Zr alloy formed by SLM SLM成形Al-Mn-Mg-Sc-Zr合金析出行为的原位TEM研究

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization

Pub Date : 2024-12-01 DOI: 10.1016/j.matchar.2024.114578

Wenhao Li , Pucun Bai , Xiaoming Cui , Xueping Zhao , Shaobo Liang , Jianlin An , Yinjun Tian

In this study, an Al-Mn-Mg-Sc-Zr alloy was prepared using the selective laser melting (SLM) technique, and the precipitation behavior during heating was characterized by In-situ transmission electronic microscopy (TEM). The results show that the microstructure of the deposited alloy is mainly composed of columnar crystals in the molten pool and equiaxed crystals at the bottom edge of the molten pool. Al₆Mn was identified as the major phase within the deposited alloy, in which Al₆Mn showed rod-shaped and particulate behavior distributed along the grain boundary of columnar crystal and equiaxed crystal. A detailed characterization of the precipitation behavior was conducted using in-situ TEM at various temperatures. At 250 °C, it was observed that the dislocation density decreased with heating time, showing no precipitation behavior, indicating good thermal stability of the alloy at this temperature. After the temperature was raised from 250 °C to 425 °C, a large number of fine and dispersed needle-rod secondary Al₆Mn phases were precipitated in the inner and bottom of the molten pool. With the increase in heating time, the size of the needle-rod secondary Al₆Mn phase increased, and no Al₃Sc precipitates were observed. However, the precipitation of Al₃Sc was found by ex-situ TEM. Thermodynamic properties of Al₃Sc and Al₆Mn were calculated by first principles. It is found that the free energy of Al₆Mn is lower than that of Al₃Sc in the temperature range of 85 to 800 K, which indicates that Al₃Sc has better thermodynamic stability than Al₆Mn.

本研究采用选择性激光熔化（SLM）技术制备了Al-Mn-Mg-Sc-Zr合金，并利用原位透射电镜（TEM）对其加热过程中的析出行为进行了表征。结果表明：沉积合金的显微组织主要由熔池内的柱状晶和熔池底边缘的等轴晶组成；沉积合金的主要相为Al6Mn， Al6Mn沿柱状晶和等轴晶晶界呈棒状和颗粒状分布。利用原位透射电镜对不同温度下的析出行为进行了详细表征。在250℃时，观察到位错密度随加热时间的延长而减小，没有析出行为，表明合金在该温度下具有良好的热稳定性。当温度从250℃升高到425℃时，熔池内部和底部析出大量细小分散的针状二次Al6Mn相。随着加热时间的延长，针杆次生Al6Mn相尺寸增大，没有Al3Sc析出。然而，通过非原位透射电镜发现了Al3Sc的析出。用第一性原理计算了Al3Sc和Al6Mn的热力学性质。在85 ~ 800 K的温度范围内，Al6Mn的自由能低于Al3Sc，表明Al3Sc比Al6Mn具有更好的热力学稳定性。

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引用次数: 0