新合金：强度是不锈钢的4倍

诸平

Thermodynamic phase predictions for metastable DP-HEA design using Thermo-Calc software. (a) Estimated equilibrium γ phase fractions and temperature onset (To) for Fe47−xMn28Co10Cr15Yx (Y: Si or Al or Ni and x: at.% contribution of selected alloying element) system in comparison with Fe50Mn30Co10Cr10 and Fe49.5Mn30Co10Cr10C0.5 alloys; (b) Effect of Si content on equilibrium γ phase fraction using Thermo-Calc and; (c) Fe47−xMn28Co10Cr15Six phase diagram obtained from Thermo-Calc showing increase in the To temperature with Si content. (Thermo-Calc simulations are based on high entropy alloy database TCHEA2).

据《达拉斯晨报》（The Dallas Morning News）的萨曼莎·格罗斯（Samantha J. Gross））2018年7月17日提供的消息，美国北德克萨斯大学（University of North Texas，UNT）的研究人员已经研制出没有泛合金（vibranium）或原-艾德曼合金 （proto-adamantium）的新合金材料。其强度是不锈钢的4倍，是一种独特的铬、钴、铁、锰和硅的混合合金。但并非Black Panther式的泛合金（Black Panther's vibranium）或Captain America式的原-艾德曼合金盾牌（Captain America's proto-adamantium shield）,而是一种由北德克萨斯大学的研究人员设计的已经相当接近其的新合金材料。

研究人员Saurabh Nene一直在与北德克萨斯大学工程学院材料科学与工程系的科研人员合作，研究混合和流动材料的同时,得到了特强合金新材料。Saurabh Nene指出，这种合金和它的虚构对手一样，没有朗朗上口的名字，它是通过熔化和铸造材料，然后用薄而平的模具开始“摩擦搅拌” 而制成的。一直致力于这方面的研究有8个月之久的Saurabh Nene说，强行将一种旋转工具插入到冰冷的金属当中，此过程会导致金属强烈变形。当将此工具插入到金属之中时,因为旋转而产生摩擦热，导致金属熔化开始混合。在取出旋转工具之前,金属的混合和流动已经形成了一种强烈变形的混合体材料。

商业化使用Saurabh Nene他们研制的合金材料唯一问题就是成本。虽然他说他无法准确估计,他试图改变合金的化学成分取代钴元素。因为钴的成本78500美元/t，而铁成本只有65美元/t。Saurabh Nene说，“我们仍在努力寻找一种廉价好的替代品,而且可以使新合金的性能不会受到影响。”

Saurabh Nene与实验室的同事迈克尔·弗兰克（Michael Frank）、刘凯淼（Kaimiao Liu音译）、布兰登·麦克威廉斯（Brandon McWilliams）以及美国马里兰州美国陆军研究实验室（U.S. Army Research Laboratory in Maryland）丘玖（Kyu Cho）合作,2018年7月2日已经在《科学报告》（Scientific Reports）在线杂志的网站发表了相关研究结果——S. S. Nene et al. Extremely high strength and work hardening ability in a metastable high entropy alloy, Scientific Reports (2018). DOI: 10.1038/s41598-018-28383-0.

Abstract

Design of multi-phase high entropy alloys uses metastability of phases to tune the strain accommodation by favoring transformation and/or twinning during deformation. Inspired by this, here we present Si containing dual phase Fe42Mn28Co10Cr15Si5 high entropy alloy (DP-5Si-HEA) exhibiting very high strength (1.15 GPa) and work hardening (WH) ability. The addition of Si in DP-5Si-HEA decreased the stability of f.c.c. (γ) matrix thereby promoting pronounced transformation induced plastic deformation in both as-cast and grain refined DP-5Si-HEAs. Higher yet sustained WH ability in fine grained DP-5Si-HEA is associated with the uniform strain partitioning among the metastable γ phase and resultant h.c.p. (ε) phase thereby resulting in total elongation of 12%. Hence, design of dual phase HEAs for improved strength and work hardenability can be attained by tuning the metastability of γ matrix through proper choice of alloy chemistry from the abundant compositional space of HEAs.

有一篇与此相关主题的论文2017年11月也在该杂志发表——S. S. Nene, K. Liu, M. Frank, R. S. Mishra, R. E. Brennan, K. C. Cho, Z. Li & D. Raabe. Enhanced strength and ductility in a friction stir processing engineered dual phase high entropy alloy. Scientific Reports, 2017, Volume 7, Article number: 16167.

Abstract

The potential of high-entropy alloys (HEAs) to exhibit an extraordinary combination of properties by shifting the compositional regime from the corners towards the centers of phase diagrams has led to worldwide attention by material scientists. Here we present a strong and ductile non-equiatomic HEA obtained after friction stir processing (FSP). A transformation-induced plasticity (TRIP) assisted HEA with composition Fe50Mn30Co10Cr10 (at.%) was severely deformed by FSP and evaluated for its microstructure-mechanical property relationship. The FSP-engineered microstructure of the TRIP HEA exhibited a substantially smaller grain size, and optimized fractions of face-centered cubic (f.c.c., γ) and hexagonal close-packed (h.c.p., ε) phases, as compared to the as-homogenized reference material. This results in synergistic strengthening via TRIP, grain boundary strengthening, and effective strain partitioning between the γ and ε phases during deformation, thus leading to enhanced strength and ductility of the TRIP-assisted dual-phase HEA engineered via FSP.

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