自然时效和Cu含量对AlMgSi(Cu)合金时效硬化行为的影响

The influences of natural ageing and Cu addition on the age hardening behavior of AlMgSi(Cu) alloys

利用硬度测试和透射电子显微镜观察,对Cu含量分别为0.0%、0.15%、0.8%(wt.%)的AlMgSi合金进行了较系统地显微组织结构和时效硬化行为研究。热处理状态为固溶淬火后直接180℃人工时效及固溶淬火后自然时效两周再180℃人工时效。结果表明:添加Cu可以抑制自然时效对180℃人工时效硬度峰值的负面作用;与固溶淬火后先自然时效两周再180℃人工时效峰值样品比较,固溶淬火后直接180℃人工时效峰值样品中针状析出相的数量密度较大;含0.15%Cu的合金峰值时效样品中只观察到β″析出相,而含0.8%Cu的合金峰值时效样品中观察到β″和Q″析出相;与不含Cu和含0.15%Cu的合金比较,含0.8%Cu的合金时效峰值出现时间延迟。这种现象与Q″相的析出有关,因为析出Q″相需要额外的时效时间。

The microstructures and age-hardening behaviors of AlMgSi alloys,whose Cu contents were 0.0%,0.15% and 0.8%（wt.%）respectively,were investigated using hardness test and transmission electron microscopy.The heat treatments of artificial ageing were performed with and without natural ageing after solution heat treatment and quenched.The results show that the Cu addition can depress the negative effect of natural aging on subsequent artificial aging,which is attributed to the increase of the quantity of needle-shaped precipitates in the samples without natural ageing.Only β″ precipitates are observed in the alloy with 0.15% Cu.Both the β″ and Q″ precipitates are observed in the alloy with 0.80% Cu alloy.Compared with the alloy without Cu and the alloy with 0.15% Cu,the occurrence time of the peak hardness for the alloy with 0.80% Cu is delayed due to the formation of Q″ precipitates.This phenomenon is related to the Q″ precipitates,because the Q″phase requires additional time to precipitate.