Effect of ultrasonic field on microstructure and mechanical properties of as-cast 7085 aluminum alloy
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The effect of an ultrasonic field on the microstructure and mechanical properties of 7085 aluminum alloy during solidification was investigated by optical microscopy, Vickers hardness test, tensile test, scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry, and electron probe micro-analysis (EPMA). The results showed that the grains of aluminum alloy were significantly refined and secondary phases were dispersed and distributed uniformly at the grain boundaries, due to ultrasonic treatment (UST). By EPMA, it was observed that the distribution of the main elements Al, Zn, Mg and Cu was more homogeneous in alloys with UST, than in alloys without UST. The mechanical properties of the aluminum alloy also significantly improved. As demonstrated by the SEM fractography of the fractured faces of several castings, fracture of the unrefined specimens occurred in a brittle manner, whereas the cracks of the refined specimens showed quasi-cleavage fracture.
Key wordsultrasonic treatment grain refinement microstructure secondary phases
本文采用金相显微分析(OM)、维氏硬度测试、扫描电子显微分析(SEM)、拉伸性能测试和电子 探针分析(EMAP)等方法研究熔铸过程中导入超声场对7085 铝合金铸锭的微观组织、力学性能的影 响。结果表明,在超声处理(UST)的作用下,铝合金的晶粒显著细化,同时第二相也更加分散。从 EPMA 的结果中观察到,经过超声处理合金中的Al、Zn、Mg 和Cu 元素分布更加均匀。铝合金的力 学性能也极大增强。从拉伸断口图中得出,常规铸锭试样的断裂方式是脆性断裂,而超声铸锭试样是 以准解理的方式断裂的。
关键词超声处理 晶粒细化 微观组织 第二相
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