Evolution of microstructure and strength of a high entropy alloy undergoing the strain-induced martensitic transformation
Evolution of microstructure and strength of a high entropy alloy undergoing the strain-induced martensitic transformation
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DOI：
10.1016/j.msea.2023.145754
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发表时间：
2023-11
期刊：
影响因子：
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通讯作者：
Jacob Weiss;D. J. Savage;Sven C. Vogel;Brandon A. McWilliams;R. Mishra;Marko Knezevic
中科院分区：
文献类型：
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作者：
Jacob Weiss;D. J. Savage;Sven C. Vogel;Brandon A. McWilliams;R. Mishra;Marko Knezevic
在最近的工作中，我们报道了一种亚稳态高熵合金（HEA）Fe 42 Mn 28 Co 10 Cr 15 Si 5（in at. %），经历了从亚稳γ奥氏体（γ）到稳定γ马氏体（ε）的应变诱发马氏体相变。然而，该合金表现出较差的延展性，这归因于其显微组织中脆性σ（σ）相的存在。本工作报告的演变的显微组织，强度和延性的类似HEA，Fe38.5Mn20Co20Cr15Si5Cu1.5（在at. %），旨在抑制σ相的形成。通过在1100 °C下退火10和30分钟并通过在150和400转/分钟（RPM）的工具旋转速率下的摩擦搅拌处理（FSP）将合金的铸造然后乳制的板处理成四种条件，以便于详细检查可变的初始晶粒结构。利用中子衍射和电子显微镜对样品的微观结构和织构进行了表征。初始材料具有不同的晶粒尺寸，但几乎100%的γ结构。在压缩变形条件下，发生无扩散应变诱发γ→ε相变，变形初期速率较高，后期速率较低，与初始晶粒尺寸无关。由于相变引起的动态Hall-Petch型势垒效应、位错密度的增加和织构，相变促进了部分塑性应变调节和快速应变硬化。在压缩下使用通过双通道FSP（150 RPM，随后150 RPM）产生的结构实现了接近2GPa的峰值强度。值得注意的是，该合金表现出的拉伸伸长率接近20%，断裂表面具有韧性韧窝和解理的组合。
In a recent work, we have reported outstanding strength and work hardening exhibited by a metastable high entropy alloy (HEA), Fe42Mn28Co10Cr15Si5(in at. %), undergoing the strain-induced martensitic transformation from metastable gamma austenite (γ) to stable epsilon martensite (ε). However, the alloy exhibited poor ductility, which was attributed to the presence of the brittle sigma (σ) phase in its microstructure. The present work reports the evolution of microstructure, strength, and ductility of a similar HEA, Fe38.5Mn20Co20Cr15Si5Cu1.5(in at. %), designed to suppress the formation ofσphase. A cast and then rolled plate of the alloy was processed into four conditions by annealing for 10 and 30 min at 1100 °C and by friction stir processing (FSP) at tool rotation rates of 150 and 400 revolutions per minute (RPM) to facilitate detailed examinations of variable initial grain structures. Neutron diffraction and electron microscopy were employed to characterize the microstructure and texture evolution. The initial materials had variable grain size but nearly 100%γstructure. Diffusionless strain inducedγ→εphase transformation took place under compression with higher rate initially and slower rate at the later stages of deformation, independent on the initial grain size. The transformation facilitated part of plastic strain accommodation and rapid strain hardening owing to a transformation-induced dynamic Hall-Petch-type barrier effect, increase in dislocation density, and texture. The peak strength of nearly 2 GPa was achieved under compression using the structure created by double pass FSP (150 RPM followed by 150 RPM). Remarkably, the tensile elongation exhibited by the alloy was nearly 20% with fracture surfaces featuring a combination of ductile dimples and cleavage.