退火处理对Al3CoCrCu1/2FeMoNiTi高熵合金激光涂层组织和性能的影响

目的研究Al_3CoCrCu_(1/2)FeMoNiTi高熵合金涂层的退火时效硬化及其强化机理。方法使用激光熔覆设备,在40Cr钢上制备了Al_3CoCrCu_(1/2)FeMoNiTi高熵合金涂层,对涂层进行了退火处理。使用X射线衍射仪、扫描电子显微镜和显微硬度计对涂层进行了分析。结果涂覆态涂层为BCC单相结构,经300℃和500℃退火,涂层仍然为BCC单相;700℃退火后,涂层析出了NiTi金属间化合物相;900℃退火后,涂层由FCC相及NiTi金属间化合物组成。涂覆态和经300~700℃退火的涂层为胞粒状,经900℃退火后,涂层为板条状。经300℃退火,涂层硬度下降,但超过300℃退火,硬度比涂覆态的高。700℃退火合金硬度达到最大值924HV。退火温度升到900℃后,硬度比700℃退火的低。NiTi析出相促进了硬度提高,位错强化机制能较好解释该高熵合金的固溶强化现象。结论Al_3CoCrCu_(1/2)FeMoNiTi合金涂层具有明显的时效硬化效应,700℃退火可获得最佳的时效硬化效果。

Effect of Annealing on the Microstructure and Property of Al3CoCrCu1/2FeMoNiTi High-entropy Alloy Laser Coating

ABSTRACT:Objective To investigate the annealing age hardening of Al3CoCrCu1/2FeMoNiTi high-entropy alloy coating and strengthening mechanism.Methods Al3CoCrCu1/2FeMoNiTi high-entropy alloy coating was deposited on 40Cr steel with laser cladding equipment, and then was annealed. X-ray diffractometer, scanning electron microscope and microhardness tester were employed to analyze microstructure and hardness.Results The original coating was of BCC single-phase structure. After annealing at 300℃ and 500℃, the coating was still of BCC structure. The coating annealed at 700℃ precipitated NiTi inter-metallic compound phase. When the annealing temperature was 900℃, the coating was composed of FCC phase and NiTi. The coating SEM morphology that was annealed at 0~700℃ was granular. After annealing at 900℃, the morphology was like lath. The coating annealed at 300℃ had a lower hardness than that of non-annealed. The hardness increased when the annealing temperature was more than 300℃. It reached the highest about 924HV at 700℃. It then became lower at 900℃. NiTi phase precipitating improved the alloy hardness. Solid solution strengthening of high-entropy alloys could be explained by dislocation strengthening mechanism.ConclusionAl3CoCrCu1/2FeMoNiTi high-entropy alloy coating obviously shows age hardening ef-fect. The alloy coating has the best hardness after annealing at 700℃.