Achieving high strength and ductility in a heterogeneous-grain-structured CrCoNi alloy processed by cryorolling and subsequent short-annealing
Achieving high strength and ductility in a heterogeneous-grain-structured CrCoNi alloy processed by cryorolling and subsequent short-annealing
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DOI：
10.1016/j.msea.2021.141610
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
Xiaoyang Zheng;W. Xie;L. Zeng;Haigen Wei;Xuihui Zhang;Hang Wang
中科院分区：
文献类型：
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作者：
Xiaoyang Zheng;W. Xie;L. Zeng;Haigen Wei;Xuihui Zhang;Hang Wang
尽管具有其他理想的性能，但具有粗晶结构的单相 CrCoNi 中熵合金 (MEA) 通常强度低得令人失望，这严重限制了其实际应用。晶粒细化可以使这种材料的强度提高数倍，但这种好处通常会导致延展性的急剧损失。在这项工作中，提出了一种由冷冻轧制和随后的短时退火组成的热机械加工方法，用于设计具有异质晶粒结构 (HGS) 的 CrCoNi MEA，以实现出色的机械性能。首先，通过冷冻轧制形成包含纳米孪晶束、纳米尺寸晶粒和位错结构区域的高度不均匀的预变形纳米结构。随后在 700°C/10 分钟下对冷冻轧制的 CrCoNi MEA 进行短暂退火，产生了晶粒尺寸从几纳米到几十微米的三级 HGS。所制备的异质 CrCoNi MEA 具有分别为 1123 ± 14 MPa 和 1453 ± 21 MPa 的超高屈服强度和拉伸强度，以及均匀伸长率为 31.2% 的大拉伸延展性，相对于通过传统轧制和后续退火制备的材料，实现了增强的强度-延展性组合。强度和延展性的非凡结合来自于异质晶粒和残余的低温变形结构效应。
Despite possessing otherwise desirable properties, the single-phase CrCoNi medium entropy alloy (MEA) with coarse grain structure generally suffer from disappointingly low strength, which severely limits its practical utility. Grain refinement can make this material several times stronger, but this benefit typically comes at a drastic loss of ductility. In this work, a thermo-mechanical processing method comprised of cryorolling and subsequent short-annealing is proposed for design of CrCoNi MEA with heterogeneous grain structure (HGS) to achieve outstanding mechanical properties. Firstly, a highly non-uniform pre-deformed nanostructure containing nanotwin bundles, nanometer-sized grains and dislocation structures regions was formed by cryorolling. Subsequent short-annealing of the as-cryorolled CrCoNi MEA at 700 °C/10 min yielded a three-level HGS with grain sizes spanning from a few nanometers up to several tens of micrometers. The as-prepared heterogeneous CrCoNi MEA exhibits ultra-high yield and tensile strengths of 1123 ± 14 MPa and 1453 ± 21 MPa, respectively, together with a large tensile ductility with a uniform elongation of 31.2%, achieving an enhanced strength–ductility combination relative to those fabricated by conventional rolling and subsequent annealing. The extraordinary combination of strength and ductility came from heterogeneous grain and residual cryo-deformation structural effect.