Cu元素对挤压剪切ZK60合金组织性能及织构演变的影响

采用金属型铸造方法制备ZK60及ZK60+1.0Cu(质量分数，%)合金，并对两种合金进行均匀化热处理与两步复合挤压剪切成形。利用OM、SEM、EDS、XRD、EBSD、TEM及室温拉伸-压缩实验研究了挤压剪切合金的显微组织、相组成及力学性能。结果表明：向ZK60合金中加入1.0Cu后，合金α-Mg基体中出现三元MgZnCu相。ZK60+1.0Cu合金成形区平均晶粒尺寸为1.56 μm，其远小于ZK60合金(4.68 μm)，且MgZnCu相附近存在着尺寸为300±45 nm的亚晶粒。相比于ZK60合金，ZK60+1.0Cu合金成形区拥有着较弱的{0001}基面织构，且织构基极和挤压方向(ED)夹角发生转变，造成ZK60+1.0Cu合金成形区中存在着更多易于{0001}<11\bar{\mathrm{2}}0>基面滑移启动的动态再结晶(DRX)晶粒。ZK60+1.0Cu合金成形区的拉伸及压缩强度明显高于ZK60合金，其主要归因于晶界强化，而拉伸伸长率的降低和硬质MgZnCu相带来的微孔聚集有关。

Effect of Cu Addition on Microstructure,Mechanical Property and Texture Evolution of Extrusion-shearing ZK60 Mg-alloy

The as-cast Mg-alloys ZK60 and ZK60+1.0Cu (mass fraction, %) were fabricated by permanent mold casting, then, the homogenization heat treatment and two-step extrusion-shearing process were performed for the alloys. The microstructure, phase constitution and mechanical properties of the extrusion-shearing alloys were characterized by means of OM, SEM, EDS, XRD, EBSD, TEM and tensile-compression test at ambient temperature. Results indicated that the ternary MgZnCu phase could be observed in the interiors of α-Mg matrix of the alloy with addition of 1.0Cu. The quantitatively measured average grain size of α-Mg matrix of ZK60+1.0Cu alloy in the forming area was 1.56 μm, which was much less than that of ZK60 alloy (4.68 μm). Furthermore, the sub-grains of 300±45 nm in size were observed around the MgZnCu phase. The ZK60+1.0Cu alloy in the forming area possessed weaker {0001} basal texture while the angle between basal pole and extrusion direction (ED) was changed as compared with ZK60 alloy, resulted in the existence of more dynamic recrystallization (DRX) grains, which was beneficial to {0001}<11\bar{\mathrm{2}}0> basal slip. The tensile and compressive strength of ZK60+1.0Cu alloy in the forming area was obviously higher than that of ZK60 alloy owing to the grain boundary strengthening, and the occurrence of micro-voids near or within the fractured MgZnCu phase mainly accounted for the decrease of tensile elongation.