预压缩变形Mg-Zn-Y-Zr合金的微观组织及时效硬化效应  

Effect of Pre-compression Mg-Zn-Y-Zr Alloy's Microstructure and Strain Aging Property

作　　者：林小娉 唐琴 叶杰 刘宁宁 孙衡 徐丹 Lin Xiaoping;Tang Qin;Ye Jie;Liu Ningning;Sun Heng;Xu Dan(School of MaterialsScience and Engineering,Northeastern University,Shenyang 110819,China;Key Laboratoryof Advanced Metal Materials and Forming Technology,Qinhuangdao 066004 ,China)

机构地区：[1]东北大学材料科学与工程学院,辽宁沈阳110819 [2]秦皇岛市先进金属材料及成型技术重点实验室,河北秦皇岛066004

出　　处：《中国稀土学报》2019年第2期217-223,I0003,共8页Journal of the Chinese Society of Rare Earths

基　　金：国家自然科学基金项目(51675092;51775099);河北省自然科学基金项目(E2018501033;E201851032;E2018501030)资助

摘　　要：对铸造Mg-8.14Zn-1.44Y-0.47Zr (%,质量分数)合金进行了0%～5%预压缩变形后,再经160℃进行等温时效处理。利用电子背散射衍射、高分辨率的透射电镜等分析手段研究了预变形镁合金的形变组织特征及其对后续时效组织、时效硬化效应的影响。结果表明:经预变形在镁合金基体中预置■拉伸孪晶和小角度晶界(位错),其小角度晶界所占百分比由1%预变形的2.6%增加到5%预变形的■拉伸孪晶变体数量随预变形量增加呈先增大后减少的趋势。160℃时效进程中,孪晶界成为准晶I-Mg_3Zn_6Y择优析出的有效衬底;而基体中存在的位错,提高了杆状或盘状β_1′-MgZn_2相析出密度,进而提高了镁合金时效初期析出速率及近峰值时效硬度; 5%预变形下达到近峰值时效硬度所需时间由未预变形的12 h缩短到6 h,近峰值时效硬度由未预变形的HV 81.5提高到HV 104.8。The as-cast Mg-8.14 Zn-1.44 Y-0.47 Zr alloy was deformed by 0%~5% pre-compression and then isothermal aged at 160 ℃. The deformed microstructure and its influence on the subsequent aging microstructure and aging hardening effect were investigated by EBSD, TEM and et al. The results showed that the pre-deformed Mg alloy introduces ■ tensile twin and low-angle grain boundaries(dislocation), the percentage of low-angle grain boundary increases from 2.6% at the pre-deformation of 1% to 15.3% at the pre-deformation of 5%. With increasing the amount of pre-deformation, the number of ■ tensile twin firstly increases and then shows a decrease trend. During the 160 ℃ aging process, the twin boundary become an effective substrate for the preferential precipitation of quasicrystal I-Mg3Zn6Y. The presence of dislocations in the matrix promotes the precipitation of rod shaped or disc shaped β1′-MgZn2 phases, which improves the precipitation rate and the near-peak aging hardness at the initial period of aging. The time for reaching the near-peak age-hardening hardness at 5% pre-deformation is shortened from 12 h(without pre-deformation) to 6 h, and the near-peak hardness increases from HV 81.5(without pre-deformation) to HV 104.8.

关 键 词：预变形 MG-ZN-Y-ZR合金 孪晶界 小角度晶界 析出相 

分 类 号：TG146.2[一般工业技术—材料科学与工程]