单晶 B2-CuZr 球晶中摩擦剪切应力诱导的不完全马氏体转变,Acta Materialia

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单晶 B2-CuZr 球晶中摩擦剪切应力诱导的不完全马氏体转变
Acta Materialia ( IF 8.3 ) Pub Date : 2024-01-23 , DOI: 10.1016/j.actamat.2024.119705
Yan Huang , Jie Dong , Ming Yang , Yibo Zhang , Zhichao Lu , Xuerui Wei , Jinkui Zhao , Wenli Song , Xiongjun Liu , Hui Wang , Xiaobin Zhang , Zhaoping Lu , Xun-Li Wang , Dong Ma

奥氏体 B2-CuZr 相在变形时会发生马氏体相变 (MT)，产生马氏体 B19'-CuZr 相，从而在 B2 结构合金中产生显着的相变诱导塑性 (TRIP) 和形状记忆效应。然而，作为 MT 以及 TRIP 和形状记忆效应基础的剪切机制和晶体学特征仍然不清楚，并且有些争议。在这里，我们报告说，{110}<001> 上的单个剪切以及作为习性平面的 {1 1 5.5} 负责 B2-CuZr 中的 MT，其中 {110} 和 <001> 是剪切面，分别为剪切方向。这些是通过明确确定 B2 和 B19' 之间的取向关系来揭示的，B2 和 B19' 共存于含 B2-CuZr 的块体金属玻璃基复合材料 (BMGC) 中所含的单个球晶中。这种奇特的微观结构是由原始单晶 B2 中的不完整 MT 制成的，其特征是每个球晶中都呈核壳状分布，其中所有 12 种可能的马氏体 (B19') 变体构成核，母体 B2 形成壳。机械研磨时受到适度摩擦剪切应力时铸态 BMGC 的球晶。有限元分析表明，B2 球晶内由较硬的玻璃基体的限制引起的核壳式剪切应力分布可能是其原因。这些结果为阐明B2→B19' MT及其在不同应力状态下的变体选择提供了直接的实验证据，并为开发延性B2结构合金铺平了道路，包括但不限于形状记忆金属间化合物、高熵合金和B2含复合材料。

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Frictional shear stress-induced incomplete martensitic transformation in mono-crystalline B2-CuZr spherulites

An austenitic B2-CuZr phase, when deformed, can undergo a martensitic transformation (MT) that produces a martensitic B19′-CuZr phase, resulting in remarkable transformation-induced plasticity (TRIP) and shape memory effects in B2-structured alloys. However, the shear mechanism as well as the crystallographic characteristics, which underlie the MT and, in turn, the TRIP and shape memory effects, remain unclear and somewhat controversial. Here we report that a single shear on {110}<001>, along with {1 1 5.5} being the habit plane, are responsible for the MT in B2-CuZr, where {110} and <001> are the shear plane and the shear direction, respectively. These were revealed by determining unambiguously the orientation relationship between B2 and B19′, co-existing in individual spherulites contained in a B2-CuZr-containing bulk metal glass-matrix composite (BMGC). This exotic microstructure, featuring a core-shell like distribution in each single spherulite in which all the 12 possible martensite (B19′) variants constitute the core and the parent B2 forms the shell, was made from an incomplete MT in originally mono-crystalline B2 spherulites of the as-cast BMGC when subjected to moderately applied frictional shear stresses upon mechanical grinding. Finite element analysis suggests that a core-shell like shear stress distribution inside a B2 spherulite, caused by the confinement of the stiffer glass matrix, may account for it. These results provide direct experimental evidence to elucidate the B2→B19′ MT and its variant selections under various stress states, and pave the way for developing ductile B2-structured alloys, including but not limited to, shape memory intermetallics, high entropy alloys and B2-containing composite materials.

更新日期：2024-01-23

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