深冷处理对双峰分离非基面织构AZ31镁合金板材室温力学性能的影响  

Effect of Cryogenic Treatment on Mechanical Behavior of AZ31 Mg Alloy Sheet with Bimodal Non-basal Texture at Room Temperature

作　　者：汪丽佳 许君怡 胡励 苗天虎 詹莎 WANG Lijia;XU Junyi;HU Li;MIAO Tianhu;ZHAN Sha(College of Materials Science and Engineering,Chongqing University of Technology,Chongqing 400054,China)

机构地区：[1]重庆理工大学材料科学与工程学院,重庆400054

出　　处：《材料研究学报》2024年第7期499-507,共9页Chinese Journal of Materials Research

基　　金：重庆市博士后研究项目(2021XM1022);重庆市教育委员会科学技术研究项目(KJQN202101141);重庆理工大学科研创新团队培育计划(2023TDZ010);重庆理工大学校级研究生创新项目(gzlcx20222004);重庆理工大学大学生创新创业训练计划项目(202311660005)。

摘　　要：将经520℃/5 h热处理的双峰分离非基面织构AZ31镁合金板材分别进行水冷处理和在液氮中深冷处理12 h,然后进行室温单轴拉伸实验并使用电子背散射衍射(EBSD)和透射电子显微(TEM)等手段表征,研究其室温力学行为和微观组织的演化。结果表明:在深冷处理和水冷处理的双峰分离非基面织构镁合金板材中,都析出了纳米相(Mg_(17)Al_(12)和Al_(8)Mn_(5))。与水冷处理的板材相比,深冷处理板材中析出相的体积分数提高了65.5%,尺寸增大了78.7%。6%和12%的室温拉伸结果表明,变形后{101ˉ2}拉伸孪晶的体积分数分别提高了38.0%和36.7%。与水冷处理板材相比,深冷处理板材的初始屈服强度和最大抗拉强度分别提高43.8%和5.2%,但是断裂延伸率降低了20.4%。强度提高的主要原因是,在深冷处理过程中生成的高密度位错、Mg_(17)Al_(12)和Al_(8)Mn_(5)纳米析出相产生了沉淀强化;断裂延伸率降低的主要原因是,在{101ˉ2}拉伸孪晶界积累的高密度位错阻碍了基面滑移,使微裂纹倾向于向高位错密度处扩展。In the present study,AZ31 Mg-alloy sheets with bimodal non-basal texture were subjected to heating treatment(520oC/5 h),and then immediately water-quenched and quenched into liquid nitrogen for 12 h.Then,their ambient temperature mechanical performance and microstructure evolution were studied by means of uniaxial tension testing,electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM).The results show that nano-precipitates Mg_(17)Al_(12)and Al_(8)Mn_(5)all exist in AZ31 Mg-alloy sheets.However,compared to the Mg-alloy sheet subjected to water-cooling treatment,the volume fraction and size of precipitates increase about 65.5%and 78.7%respectively for the sheet subjected to cryogenic treatment.Meanwhile,the volume fraction of{101¯2}extension twin(ET)increases by 38.0%and 36.7%for the sheet being subjected to 6%and 12%deformation,respectively.The yield strength(YS)and ultimate tensile strength(UTS)of the cryogenic treated sheets are increased by 43.8%and 5.2%,respectively,compared with the water-cooling treated ones,however,the fracture elongation(FE)decreases by 20.4%.The increase in YS and UTS may mainly be due to the generation of high-density dislocations and precipitation strengthening by Mg_(17)Al_(12)and Al_(8)Mn_(5)precipitates during cryogenic treatment.The decrease in FE is mainly due to the accumulation of high-density dislocations near{101¯2}ET boundaries during tensile deformation at room temperature,which would hinder the movement of basal slip and benefit in propagation of microcracks to expand to this region.

关 键 词：金属材料 非基面织构AZ31镁合金 深冷处理 微观组织演化 塑性变形机制 

分 类 号：TG146.22[一般工业技术—材料科学与工程]