The extrusion process parameters were optimized based on Deform 2D finite element simulation,aluminum magnesium bimetal composite extrusion experiment was conducted under the extrusion rate of 2mm/s and extrusion temperature of 470℃.The microstructure of interface bonding layer was observed and analyzed by using scanning electron microscopy(SEM),microhardness test and electron backscattering diffraction(EBSD).The results show that interface layer generates in the contact region of aluminum and magnesium alloys,new phases in the layer are Al12Mg17 which is close to the AZ31 magnesium substrate and Al3Mg2 which is close to the aluminum substrate.The average microhardness value of Al3Mg2 phase is the highest,the average value is about 210HV,and that of Al12Mg17 is 170HV,the interface area forms a typical brittle layer as the hardness is higher than the parent metal on both substrate sides,the EBSD test shows that the average grain size of Al12Mg17 phase is 30μm,the average grain size of Al3 Mg2 phase is about 20μm,different grain orientation can be observed in composite interface bonding layer regional and the grain size is not uniform,the outer pure aluminum matrix composite orientation area is uniform,some recrystallization of new generation phase occurs on the grain boundary.%基于Deform 2D有限元模拟优化挤压工艺参数,在挤压速率2mm/s,挤压温度470℃下对铝镁双金属进行复合挤压实验,并采用扫描电镜(SEM)、显微硬度测试以及电子背散射衍射(EBSD)对复合挤压件界面结合层进行微观组织观察与分析.结果表明:在铝镁合金接触区反应生成了界面层,层内新的物相为靠近AZ31镁基体一侧的Al12Mg17以及靠近铝基体一侧的Al3Mg2.Al3Mg2相显微硬度值最高,平均值约为210HV,Al12Mg17相平均硬度约为170HV,因而界面区硬度高于两侧基体母材,形成典型的脆硬结合层,电子背散射衍射(EBSD)结果显示,Al12Mg17相的平均晶粒尺寸为30μm,Al3Mg2相的平均晶粒尺寸约为20μm,复合界面结合层区域晶粒取向各异,晶粒尺寸大小也不均匀,而复合外层纯铝基体取向区域均匀,新生成相在晶界上有部分再结晶发生.
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