挤压-室温轧制对尺寸不对称喷射沉积含Gd镁合金组织及织构影响

Microstructure and Texture of Dimensional Asymmetric Spray Deposited Magnesium Alloy Containing Gd by Extruding-Rolling

摘要：采用喷射沉积技术制备Mg-8Zn-2Ca-2Gd-1Zr-1Nd合金沉积坯，对其进行挤压预变形后再进行室温轧制变形（ε=5％，10％，15％）。利用蔡司金相显微镜（OM），扫描电子显微镜（SEM）和x射线衍射仪（XRD）分析挤压-轧制变形对镁合金显微组织及微观织构演变的影响。结果表明：尺寸不对称喷射沉积镁合金挤压坯在室温轧制变形时，随压下率（8.5％，10％，15％）增加，硬度值升高且存在硬度值分布不均匀现象，团聚第二相粒子逐渐呈弥散分布，其中尺寸小于1μm的第二相粒子弥散分布于基体上，而部分富稀土元素第二相碎化后偏聚在基体晶粒晶界处，大量弥散分布于基体和晶界处的第二相粒子阻止位错滑移是镁合金轧制后硬度提高的重要原因。尺寸不对称喷射沉积镁合金在挤压-轧制变形过程中，当F=10％时，（0002）基面织构强度降低、非基面织构形成且极密度增强，实现了形变织构随机化。晶粒细化、挤压坯初始织构遗传性、尺寸不对称变形三者综合作用是实现形变织构随机化的主要原因。

The billets of Mg-8Zn-2Ca-2Gd-lZr-lNd alloy were prepared by spray-deposition （the Osprey process）. And room temperature rolling deformation （ε=5%, 10%, 15% ） following the hot extrusion was carried out. The effects of extruding-rolling deformation on the microstructure and texture evolution of magnesium alloy were investigated by Zeiss metallographic microscope （ OM）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Results showed that for the size asymmetric extruded billet of magnesium alloy during the room temperature rolling deformation, as pass reduction increased （ε= 5% , 10% , 15% ） , hardness values increased and its distribution showed non-uniformity. Agglomeration secondary phases dispersed gradually, wherein the second phase particles with a size less than 1 ~zm dispersed in the matrix, while shredded secondary phases enriched rare earth elements segregated at the matrix grain boundary. A large number of secondary phase were dispersed in the matrix and grain boundaries which could prevent dislocation slip, and that was an important reason for the increase of hardness of magnesium alloy after rolling deformation. During the extruded-rolling deformation of dimensional asymmetric Mg alloy, at ε = 10% , the basal texture strength of （0002） was reduced, prismatic texture and pyramidal texture appeared and enhanced, namely, deformation texture realized randomization. It was noted that the combined effect of grain refinement, initial texture heredity of extruded billet and size asymmetric deformation were the main reasons to realize texture randomization.