Achieving strength-ductility synergy of spark plasma sintered (CoCrNi)94Al3Ti3 medium-entropy alloy via post-sintering in-situ precipitation treatment

IF 6.2 2区 材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY
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Abstract

The single-phase face-centered cubic medium-entropy alloys (MEAs) normally have coarse grains in as-cast state, which exhibit insufficient strength for engineering applications. Here, a superior tensile strength-ductility synergy in a fine grained (CoCrNi)94Al3Ti3 MEA hardened by nanoscale L12 precipitates was fabricated by spark plasma sintering (SPS) and post-sintering in-situ precipitation treatment. The SPSed MEAs have a fine grain size of ⁓ 5 μm, and a high number density of L12 precipitates form after in-situ annealing within the SPS machine. A high tensile yield strength of 1141 MPa with an adequate elongation to fracture of 25.8% was achieved in (CoCrNi)94Al3Ti3 MEA after annealing at 700 °C for 4 h. Electron backscattered diffraction and transmission electron microscopy characterizations indicate that the superior mechanical properties mainly originate from fine grains and the coherent spherical L12 precipitates. The dislocation slips and stacking faults prevail in all SPSed MEAs during tensile deformation, while extra Lomer-Cottrell locks are observed in annealed MEAs. The deformation twinning is absent in these precipitation-hardened MEAs with a low stacking fault energy, which may be attributed to the fine grains and numerous nanoscale L12 precipitates. This study not only confirms the effectiveness of powder metallurgy when sintering and precipitation are combined in-situ during the SPS cycle, but also provide guidance for the microstructure regulation process and practical applications of SPSed HEAs/MEAs.

通过烧结后原位沉淀处理实现火花等离子烧结 (CoCrNi)94Al3Ti3 中熵合金的强度-韧性协同效应
单相面心立方中熵合金(MEA)在铸造状态下通常晶粒较粗,在工程应用中强度不足。在这里,通过火花等离子烧结(SPS)和烧结后原位沉淀处理,制造出了由纳米级 L12 沉淀硬化的细晶粒 (CoCrNi)94Al3Ti3 MEA,并在其中实现了卓越的拉伸强度和电导率协同作用。经 SPS 处理的 MEA 晶粒大小为 ⁓ 5 μm,在 SPS 设备内原位退火后形成了高密度的 L12 沉淀。电子反向散射衍射和透射电子显微镜表征表明,优异的机械性能主要源于细晶粒和相干球形 L12 沉淀。所有 SPSed MEA 在拉伸变形过程中都普遍存在位错滑移和堆积断层,而在退火的 MEA 中则观察到额外的 Lomer-Cottrell 锁。这些堆叠断层能量较低的沉淀硬化 MEA 中不存在变形孪晶,这可能是由于晶粒较细和存在大量纳米级 L12 沉淀所致。这项研究不仅证实了粉末冶金在 SPS 循环中烧结与沉淀原位结合的有效性,还为 SPSed HEAs/MEEA 的微观结构调节过程和实际应用提供了指导。
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来源期刊
Journal of Materials Research and Technology-Jmr&t
Journal of Materials Research and Technology-Jmr&t Materials Science-Metals and Alloys
CiteScore
8.80
自引率
9.40%
发文量
1877
审稿时长
35 days
期刊介绍: The Journal of Materials Research and Technology is a publication of ABM - Brazilian Metallurgical, Materials and Mining Association - and publishes four issues per year also with a free version online (www.jmrt.com.br). The journal provides an international medium for the publication of theoretical and experimental studies related to Metallurgy, Materials and Minerals research and technology. Appropriate submissions to the Journal of Materials Research and Technology should include scientific and/or engineering factors which affect processes and products in the Metallurgy, Materials and Mining areas.
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