Abstract

Al_xCoCrFeNi high entropy alloy (HEA) system has received extensive attention of researchers as it shows a dynamic change in phase fraction and properties in response to variation in the Al content. In this study, Al_xCoCrFeNi HEAs were welded using a laser beam welding and microstructural evolution and mechanical properties were studied using X-ray diffraction, electron backscatter diffraction, scanning electron microscopy, hardness and tensile tests. Results revealed that, the laser-welded Al_0.3 alloy exhibited an increased tensile strength but a minor decrease in ductility as compared to that of the base metal (BM) Conversely, the laser-welded Al_0.5 and Al_0.7 alloys, characterized by a dual-phase structure, demonstrated a simultaneous decrease in both strength and ductility. The hardness of Al_0.3 increased from 156 HV for base metal (BM) to 197 HV for weld zone (WZ). A drastic drop in the hardness in the fusion zone was observed for Al_0.5 (from 242 HV for BM to 212 HV for WZ) and Al_0.7 (from 387 HV for BM to 260 HV for WZ). The decrease in hardness for welded Al_0.5 and Al_0.7 alloy may be attributed to reduced fraction of secondary BCC/B2 phase in the microstructure. Texture analysis of the welded samples reveals columnar grains with a \(<100>\parallel {\text{ND}}\) texture fibre in the welded Al_0.3 and Al_0.5 alloys. However, the welded Al_0.7 alloy has a dendritic structure with random texture due to the enhanced rate of constitutional supercooling arising from the higher fraction of secondary phases. The combined effect of changes in phase distribution, texture, and grain size might be the reasons for the variation in mechanical properties of the welded alloy.

Graphical abstract

中文翻译：

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激光束焊接AlxCoCrFeNi高熵合金的显微组织演变和力学性能

摘要

Al _x CoCrFeNi高熵合金（HEA）体系受到了研究人员的广泛关注，因为它表现出相分数和性能随Al含量变化的动态变化。在本研究中，使用激光束焊接Al _x CoCrFeNi HEA，并使用 X 射线衍射、电子背散射衍射、扫描电子显微镜、硬度和拉伸测试研究微观结构演变和机械性能。结果表明，与母材 (BM) 相比，激光焊接的 Al _{0.3合金的拉伸强度有所提高，但延展性略有下降；相反，激光焊接的 Al 0.5}和 Al _0.7合金的特点是双-相结构，表明强度和延展性同时下降。 Al _0.3的硬度从母材 (BM) 的 156 HV 增加到焊缝区 (WZ) 的 197 HV。观察到 Al _0.5（从 BM 的 242 HV 到 WZ 的 212 HV）和 Al _0.7（从 BM 的 387 HV 到 WZ 的 260 HV）熔合区硬度急剧下降。焊接 Al _0.5和 Al _0.7合金的硬度降低可能是由于显微组织中二次 BCC/B2 相比例的降低。焊接样品的织构分析揭示了焊接 Al _0.3和 Al _{0.5合金中具有}\(<100>\parallel {\text{ND}}\)织构纤维的柱状晶粒。然而，焊接的Al _0.7合金由于第二相含量较高而提高了组织过冷速率，因此具有随机织构的枝晶结构。相分布、织构和晶粒尺寸变化的综合影响可能是焊接合金机械性能变化的原因。

图形概要