旋轉(zhuǎn)摩擦擠壓7075鋁合金組織及第二相形貌

旋轉(zhuǎn)摩擦擠壓7075鋁合金組織及第二相形貌Microstructure and second phase morphology of rotational friction extruding 7075 Al alloy

采用旋轉(zhuǎn)摩擦擠壓法(RFE)加工T6態(tài)7075鋁合金，對擠壓后的7075鋁合金進(jìn)行熱處理，觀察了7075鋁合金的顯微組織和第二相變化，測試了加工后材料的顯微硬度。結(jié)果表明，RFE態(tài)的7075鋁合金為未完全再結(jié)晶的細(xì)小等軸晶，平均晶粒尺寸約為15 μm。經(jīng)熱處理后，鋁合金中未發(fā)生再結(jié)晶的晶粒繼續(xù)完成再結(jié)晶，晶粒尺寸進(jìn)一步細(xì)化均勻，約為8 μm。RFE加工使7075鋁合金中保留的初生金屬間化合物尺寸變小，原沉淀析出的第二相(MgZn2相)在RFE加工過程中大部分發(fā)生重溶，未重溶的MgZn2相發(fā)生粗化，經(jīng)熱處理后7075鋁合金中析出的MgZn2相尺寸細(xì)小，呈彌散分布。RFE態(tài)7075鋁合金顯微硬度低于基材，但經(jīng)T6熱處理后，其硬度為177.5HV，高于基材，7075鋁合金中第二相對基體的強(qiáng)化效果較細(xì)晶強(qiáng)化作用更顯著。

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.

全文下載：http://pan.baidu.com/s/1c26HZUC