采用旋转摩擦挤压法(RFE)加工T6态7075铝合金,对挤压后的7075铝合金进行热处理,观察了7075铝合金的显微组织和第二相变化,测试了加工后材料的显微硬度.结果表明,RFE态的7075铝合金为未完全再结晶的细小等轴晶,平均晶粒尺寸约为15μm.经热处理后,铝合金中未发生再结晶的晶粒继续完成再结晶,晶粒尺寸进一步细化均匀,约为8μm.RFE加工使7075铝合金中保留的初生金属间化合物尺寸变小,原沉淀析出的第二相(MgZn2相)在RFE加工过程中大部分发生重溶,未重溶的MgZn2相发生粗化,经热处理后7075铝合金中析出的MgZn2相尺寸细小,呈弥散分布.RFE态7075铝合金显微硬度低于基材,但经T6热处理后,其硬度为177.5HV,高于基材,7075铝合金中第二相对基体的强化效果较细晶强化作用更显著.%7075-T6 Al alloy with T6 state was processed by Rotational friction extrusion (RFE), and then they were heat treated. The microstructure and second phase of 7075 Al alloy were observed, the hardness was tested. The results show that, 7075 Al alloy after RFE is composed of fine equiaxed grains while they are recrystallized uncompletely, average grain size is about 15 μm. After heat treatment, the recrystallization behavior is finished in those unrecrystallized grains and grain becomes finer, about 8 μm. The primary intermetallic reserved in 7075 Al alloy becomes smaller after RFE. Most of aging precipitated phase (MgZn2) is re-dissolved, however, some un-dissolved precipitated phase particles become coarser. Many new second phase particles are re-precipitated in the extruded 7075 Al alloy after heat treatment, and they are distributed uniformly. The hardness of the as-RFE 7075 Al alloy is lower than that of the as-recieved material, but after T6 heat treatment, the hardness is 177.5HV, higher than that of the as-received material. The strengthening effect of second phase is greater than that of fine-grain in 7075 Al alloy.
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