Research On Processing Technology Of Pre-deformation And Forward Extrusion Twist Deformation Of Magnesium Alloy For Aerospace

As competitive structure materials to aluminum alloys,magnesium alloys have great potential application on aviation,due to their high specific strength,low density.As the magnesium alloy is Hexagonal Close-Packed structure,it is difficult to carry out the further plastic deformation at room temperature.However,the microstructure of the processed alloys is still not uniform with strong basal texture,especially in those alloys after conventional extrusion,resulting in poor mechanical properties.The AQ80 magnesium alloy is extruded by the new process of pre-deformation and forward extrusion twist deformation?composite process?to improve its mechanical properties.The constitutive equation and processing map of pre-deformed AQ80 magnesium alloy were established by experiment of hot compression under different deformation conditions(deformation temperature:250⁴00?,strain rate:0.001⁵s^-1).The finite element analysis of the compound forming process was carried out,taking constitutive equation of pre-deformed AQ80 magnesium alloy as the material base.The effects of different forward extrusion twist deformation?FETD?structure parameters on the equivalent strain,metal flow velocity and extrusion force of pre-deformed AQ80 magnesium alloy were analyzed.Experimental study on composite process based on the results of finite element analysis.The conclusions can be summarized as follows:?1?The flow stress of pre-deformed AQ80 magnesium alloy decreases with the decrease of strain rate and the increase of temperature.Combining analysis of hot processing map and the corresponding microstructure at each domain,stability regions were identified to be at the temperature range of 300⁴00?and strain rate of 0.001⁰.01s^-1.?2?According to finite element analysis of composite process of extrusion process,when the twist angle?=30°and the torsion length L=15mm,it helps to improve the FETD die extrusion capacity.?3?The grain size of AQ80 magnesium alloy after the composite process is obviously refined,and the grain size increases with the extrusion temperature increasing?310?,340?,370?,400??.Low temperature?310??and high temperature?400??have different effects on the microstructure evolution.The microstructure and the second phase are very uniform at310?,and the pre-deformation process plays a good role in regulating the microstructure.And the effect of the pre-deformation process at 400?is not obvious,the microstructure and the second phase are coarse and unevenly distributed.?4?Basal texture strength of AQ80 magnesium alloy by composite process compared to the traditional extrusion process significantly weakened,but the texture strength of the AQ80magnesium alloy at high temperature?400??was higher than that of the low temperature?310??.?5?With extrusion temperature of composite process increasing,the compression rate???of AQ80 magnesium alloy gradually increased,and?is 16.3%,18.1%,21.5%and 22.8%,respectively.While the yield strength?YS?tends to decrease on the whole,as follows:192Mpa?195Mpa?130Mpa?119Mpa,ultimate compression strength?UCS?is 462Mpa?469Mpa?481Mpa?457Mpa,respectively.When the extrusion temperature is 370?,the strength-toughness properties of AQ80 magnesium alloy are better.