Laser-directed energy deposition of a high performance additively manufactured (CoCrNi)94(TiAl)6 medium-entropy alloy with a novel core-shell structured strengthening phase
Laser-directed energy deposition of a high performance additively manufactured (CoCrNi)94(TiAl)6 medium-entropy alloy with a novel core-shell structured strengthening phase
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DOI：
10.1016/j.addma.2024.103971
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发表时间：
2024-01
影响因子：
11
通讯作者：
Xiaolin Bi;Ruifeng Li;Zijian Yuan;Jiangbo Cheng;Dikai Guan;Peilei Zhang
中科院分区：
文献类型：
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作者：
Xiaolin Bi;Ruifeng Li;Zijian Yuan;Jiangbo Cheng;Dikai Guan;Peilei Zhang
采用激光定向能沉积法制备了(CoCrNi)94(TiAl)6中熵合金(MEAs)。用电子背散射和透射电子显微镜研究了(CoCrNi)94(TiAl)6MEAs的强化诱导机制。结果表明，TiAl粉末的加入使合金在298K时的极限拉伸强度(UTS)和屈服强度(YS)分别提高了29.6%和43.5%，延伸率降低了17.1%。在77K下加入TiAl粉末后，抗拉强度和延伸率分别提高了26.6%和28.0%，延伸率提高了26.3%。显微组织观察结果表明，基体组织由生长方向均匀的原始柱状晶转变为细小的枝晶组织。在添加制备的(CoCrNi)94(TiAl)6MEAs中发现了大量具有新型核壳结构的纳米TiO3TiO3TiO4强化相，两者都具有面心立方结构。未观察到纳米析出物与基质之间的结晶取向。在298℃时，位错线绕过纳米析出物，在纳米析出物附近出现Lmer-Cottrell锁定，从而强化了(CoCrNi)94(TiAl)6MEAs。在77℃下，塑性变形导致纳米析出相和基体的协同变形，大量位错的形成，孪晶诱发塑性效应，进一步提高了添加制备的(CoCrNi)94(TiAl)6MEAs的强度和塑性。
Additively manufactured (CoCrNi)94(TiAl)6medium-entropy alloys (MEAs) were fabricated by laser-directed energy deposition. The strengthening induction mechanism in the additively manufactured (CoCrNi)94(TiAl)6MEAs was investigated using electron backscatter diffraction and transmission electron microscopy. The results showed that the addition of TiAl powder led to increases of 29.6% and 43.5% in the ultimate tensile strength (UTS) and yield strength (YS), respectively, at 298 K, and a decrease of 17.1% in the elongation. For the samples tested at 77 k after the addition of the TiAl powder, the UTS and YS improved by 26.6% and 28.0%, respectively, and the elongation increased by 26.3%. The microstructural observation results indicated that the matrix grains changed from initial columnar grains with a uniform growth direction to fine dendrites. Numerous TiO clad Al2O3strengthening nano-precipitates with a novel core–shell structure were found in the additively manufactured (CoCrNi)94(TiAl)6MEAs, and both featured a face-centered cubic structure. No crystallographic orientation was observed between the nano-precipitates and the matrix. At 298 K, the dislocation line bypassed the nano-precipitates during the plastic deformation period and Lomer–Cottrell locks appeared near the nano-precipitates, thereby strengthening the additively manufactured (CoCrNi)94(TiAl)6MEAs. At 77 K, plastic deformation resulted in the synergistic deformation of the nano-precipitates and matrix, the formation of a large number of dislocations, and a twinning induced plasticity effect, which further increased the strength and plasticity of the additively manufactured (CoCrNi)94(TiAl)6MEAs.