Al-Mg-Si-Cu合金中晶界和晶内析出相粗化规律的研究

An electron microscopy study of precipitate coarsening in Al-Mg-Si-Cu alloys

采用显微硬度测试仪、扫描电镜和透射电镜观察及能谱分析,研究了Al-0.5Mg-1.0Si-0.8Cu(wt.%)合金的晶界析出规律和晶内析出相的粗化机制。结果表明:180℃时效处理的Al-0.5Mg-1.0Si-0.8Cu(wt.%)合金晶界处存在富Si相和Q相两类不连续分布的析出相,它们的尺寸分别约为1 mm和几十纳米;时效0.5 h时晶界处有少量富Si相,时效5 h时晶界富Si相明显增多,时效36 h时富Si相开始粗化且间距变大,再进一步时效其形貌和分布变化不大;晶界Q相与相邻晶粒铝基体的界面取向关系是:[510]Al//[1120]Q;时效36 h晶内开始出现粗化析出相,且随时效继续进行合金晶内析出大量粗化相,存在明显的晶界无析出带现象。晶内粗化析出相主要含有Si元素,呈片状、球状和棒状3种形貌。其中,棒状Si析出相是沿〈001〉Al方向生长的,且〈112〉Si//〈001〉Al,{111}Si//{010}Al。

The phenomenon of grain boundary precipitation and intragranular precipitate coarsening in an Al-0.5Mg-1.0Si-0.8Cu（wt.%） alloy were investigated by micro-hardness tester,scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and energy dispersive X-ray spectroscopy（EDS）.The experimental results show that two types of discontinuous grain boundary precipitates exist during artificial aging：（1） Si-rich particles of about 1 μm and（2） Q-phase particles of 10~30 nm.For the samples aged for 0.5 h,very few Si-rich precipitates were observed.After aging for 5 h,the number of Si-rich particles obviously increased.The size of Si-rich particles increases with the aging time until 36 h,and stays unchanged afterwards.The grain boundary Q phase has also the specific orientation with one of the two grains： 〈510〉Al//〈1120〉Q.Although the grain boundary precipitates stop coursing after 36 h of aging,the intragranular precipitates continue growing and eventually form an observable precipitate free zone along the grain boundaries.TEM and EDS analyses indicate that the intragranular precipitates are Si precipitates,possessing platelet,globule or rod morphologies.The rod-like Si precipitates grow along 〈001〉Al,and have a orientation relationship with Al matrix： 〈112〉Si//〈001〉Al,{111}Si//{010}Al.