高塑性Mg-Gd-Zn镁合金管材的组织和力学性能研究

Microstructure and mechanical properties of extruded Mg-3%Gd-1%Zn seamless tubes with high-ductility

为了制备高塑性镁合金无缝管材,将具有不同初始组织的Mg-3%Gd-1%Zn(质量分数/%,以下简称GZ31)合金空心锭在420～480℃挤压成无缝管材,采用金相显微镜、扫描电镜、X射线衍射分析和拉伸试验等表征了管材的组织和力学性能.结果表明:GZ31镁合金无缝管材较AZ31具有更弱的基面纤维织构;420℃一次挤压成形的GZ31管材由于组织中还存在粗大的原始晶粒,导致室温伸长率较低;440℃及以上挤压时得到完全再结晶组织,且随挤压温度升高,再结晶晶粒和第二相尺寸逐渐增大;经过一次挤压开坯后再在440℃二次挤压的无缝管材具有更细小的平均晶粒尺寸(约12μm),其室温伸长率高达35%,明显优于传统AZ31以及一次挤压成形的GZ31镁合金无缝管材.

To manufacture high ductile magnesium alloy seamless tubes,Mg-3%Gd-1%Zn（wt%,called GZ31 bellow） alloy hollow billets with different initial microstructures were extruded as tubes at 420~480 ℃,and methods of optical microcopy（OM）,scanning electron microscopy（SEM）,X-ray diffraction and tensile tests were used to measure their microstructures and tensile room-temperature mechanical properties.Results show that the GZ31 tubes have a weaker basal plane fiber texture than AZ31.For one-step extrusion with casting billets,grains of tube extruded at 420 ℃ is finer,but a few coarse unrecrystallized grains still exist in microstructure,so that the tube has an inferior room temperature tensile elongation.The tubes extruded at 440 ℃ or higher temperatures have completely recrystallized microstructure,and as extrusion temperature increases,the sizes of recrystallized grains and second phases increase roughly.However,the tubes being secondarily extruded at 440 ℃ with first-extrusion billets have a finer grain size of 12 μm and the maximum room-temperature tensile elongation is of 35%,which is much better than that of conventional AZ31 alloy tubes and the one-step extruded GZ31 tubes.