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Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys
Advanced Materials ( IF 29.4 ) Pub Date : 2018-09-14 , DOI: 10.1002/adma.201804727
Wenjun Lu 1 , Christian H. Liebscher 1 , Gerhard Dehm 1 , Dierk Raabe 1 , Zhiming Li 1
Affiliation  

Microstructural length‐scale refinement is among the most efficient approaches to strengthen metallic materials. Conventional methods for refining microstructures generally involve grain size reduction via heavy cold working, compromising the material's ductility. Here, a fundamentally new approach that allows load‐driven formation and permanent refinement of a hierarchical nanolaminate structure in a novel high‐entropy alloy containing multiple principal elements is reported. This is achieved by triggering both, dynamic forward transformation from a faced‐centered‐cubic γ matrix into a hexagonal‐close‐packed ε nanolaminate structure and the dynamic reverse transformation from ε into γ. This new mechanism is referred to as the “bidirectional transformation induced plasticity” (B‐TRIP) effect, which is enabled through a near‐zero yet positive stacking fault energy of γ. Modulation of directionality in the transformation is triggered by local dissipative heating and local micromechanical fields. The simple thermodynamic and kinetic foundations for the B‐TRIP effect render this approach generally suited for designing metastable strong and ductile bulk materials with hierarchical nanolaminate substructures.

中文翻译:

双向转变可实现分层纳米层压双相高熵合金

微观结构的长度尺度细化是增强金属材料的最有效方法之一。用于细化微结构的常规方法通常包括通过大量的冷加工来减小晶粒尺寸,从而损害了材料的延展性。在这里,报道了一种根本上新的方法,该方法允许在包含多个主要元素的新型高熵合金中进行载荷驱动的形成和永久细化分层纳米层压结构。这可以通过触发从面心对立的γ矩阵到六方密堆积的ε纳米层状结构的动态正向转换以及从ε到γ的动态反向转换来实现。这种新机制被称为“双向转化诱导可塑性”(B‐TRIP)效应,这是通过接近零但正的堆叠故障能量γ启用的。局部耗散加热和局部微机械场触发了转变中方向性的调节。B‐TRIP效应的简单热力学和动力学基础使得该方法通常适用于设计具有分层纳米层状亚结构的亚稳强韧且易延展的块状材料。
更新日期:2018-09-14
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