Modifying transformation pathways in high entropy alloys or complex concentrated alloys via thermo-mechanical processing
Modifying transformation pathways in high entropy alloys or complex concentrated alloys via thermo-mechanical processing
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DOI：
10.1016/j.actamat.2018.05.009
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发表时间：
2018-07-01
期刊：
影响因子：
9.4
通讯作者：
Banerjee, Rajarshi
中科院分区：
文献类型：
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作者：
Gwalani, Bharat;Gorsse, Stephane;Banerjee, Rajarshi
通常，实验观察到的单相高熵合金（HEA）是由热力学和动力学因素约束的第二相沉淀的结果。使用Al0.3CoCrFeNi作为候选HEA，本文证明了强烈的影响，热机械加工的转变途径，通过等温第二相沉淀。传统的热机械加工路线包括在单一fcc相区域中的均匀化冷轧固溶处理，随后在较低温度下的沉淀退火，导致纳米尺度有序的L1（2）（类γ素数）沉淀物在fcc基体内均匀分布。相比之下，如果冷轧后直接在沉淀温度下退火，则所得的显微组织演化路径完全改变，同时发生基体fcc晶粒的再结晶和B2和σ相的沉淀，主要在晶界处。这些实验观察到的转变途径的变化已经合理化，通过在该合金中的第二相成核的热力学驱动力和激活势垒之间的竞争，再加上动力学的过程。从这些显着不同的相变途径导致的微观结构的变化，可以导致一些相当特殊的机械性能，可以在很大的范围内变化，即使是一个单一的Al0.3CoCrFeNi HEA组合物。由Elsevier Ltd代表Acta Materialia Inc.发布
Often the experimentally-observed, single-phase high entropy alloy (HEA) is the result of second-phase precipitation constrained by thermodynamic and kinetic factors. Using Al0.3CoCrFeNi as a candidate HEA, this paper demonstrates the strong influence of thermo-mechanical processing on the transformation pathway adopted for isothermal second-phase precipitation. A traditional thermo-mechanical processing route comprised of homogenization cold-rolling solution treatment in the single fcc phase region, followed by a precipitation anneal at a lower temperature, results in a homogeneous distribution of nanometer scale-ordered L1(2) (gamma prime-like) precipitates within the fcc matrix. In contrast, if cold-rolling is followed directly by annealing at the precipitation temperature, then the resulting microstructural evolution pathway changes completely, with concurrent recrystallization of the matrix fcc grains and precipitation of B2 and sigma phases, largely at the grain boundaries. These experimentally observed variations in transformation pathway have been rationalized via the competition between the thermodynamic driving force and activation barrier for second-phase nucleation in this alloy, coupled with the kinetics of the process. The microstructural variations that result from these dramatically different phase transformation pathways can lead to some rather exceptional mechanical properties that can be varied over a large range even for a single Al0.3CoCrFeNi HEA composition. Published by Elsevier Ltd on behalf of Acta Materialia Inc.