搅拌摩擦加工增强LA103Z镁锂合金超塑性  

Enhancing superplasticity of LA103Z magnesium-lithium alloy by friction stir processing

作　　者：宋文杰 辛彬彬 贺帅 吴宗育 杨光 李誉之 SONG Wenjie;XIN Binbin;HE Shuai;WU Zongyu;YANG Guang;LI Yuzhi(College of Mechanical&Electrical Engineering,Shaanxi University of Science&Technology,Xi’an 710021,China;Department of Materials Science,Fudan University,Shanghai 200438,China)

机构地区：[1]陕西科技大学机电工程学院,西安710021 [2]复旦大学材料科学系,上海200438

出　　处：《中国有色金属学报》2024年第3期763-776,共14页The Chinese Journal of Nonferrous Metals

基　　金：国家自然科学基金资助项目(52201265);陕西省重点研发计划资助项目(2023-YBGY-294,2023KXJ-060);陕西科技大学博士科研启动基金资助项目(2016GBJ-02)。

摘　　要：利用搅拌摩擦加工(FSP)对热轧态LA103Z镁锂合金板材进行改性,研究了FSP-LA103Z合金在温度为200~350℃、应变速率为5×10^(−4)~1×10^(−2)s^(−1)时的超塑性变形行为,揭示了FSP-LA103Z合金的超塑性变形机制。结果表明:当在温度为300℃、应变速率为1×10^(−3)s^(−1)时,FSP-LA103Z合金的伸长率约为430%,曲线为流变应力稳定型,该条件下的应变速率敏感系数m为0.55。在FSP-LA103Z合金的超塑性变形过程中,β-Li晶粒长大并重新排列,其晶界扭曲畸变;α-Mg相经析出、断裂、长大,呈等轴状或球状在晶界均匀分布,部分重新聚合;AlLi相的固溶析出促进位错滑移从而协调晶内变形。在变形前期,β-Li主导变形,细小α-Mg抑制β-Li生长。在变形后期,α-Mg主导变形,β-Li晶粒沿着拉伸方向规律排布,使得β/β界面阻力增大不利于变形。此时,FSP-LA103Z合金主要由α/β界面滑移及α-Mg晶粒转动协调变形,随着空洞的形核、长大、合并,最终导致板材断裂。Hot rolled LA103Z magnesium-lithium alloy sheets were modified by friction stir processing(FSP).The superplastic deformation behavior of FSP-LA103Z Mg-Li alloy at the temperatures of 200−350℃and strain rates of 5×10^(−4)−1×10^(−2)s^(−1)was studied,and the superplastic deformation mechanism was revealed.The results show that,when the deformation temperature is 300℃and the strain rate is 1×10^(−3)s^(−1),the elongation of FSP-LA103Z Mg-Li alloy is about 430%,the stress−strain curve is flow stress stable,the strain rate sensitivity coefficient m under this condition is 0.55.During superplastic deformation of FSP-LA103Z Mg-Li alloy,β-Li grains grow and rearrange,and their grain boundaries are distorted.Theα-Mg phases precipitate,fracture and grow up,as equiaxed or spherical grains,uniformly distribute in grain boundaries,and partially repolymerize.Solid solution precipitation of AlLi promotes dislocation slip and coordinates intracrystalline deformation.At the early stage of deformation,β-Li dominated deformation,and fineα-Mg phases inhibiteβ-Li growth.In the later stage of deformation,α-Mg phases dominate the deformation,andβ-Li grains are arranged regularly along the tensile direction,which makes the increase ofβ/βinterface resistance unfavorable to deformation.At this time,α/βinterface slip andα-Mg grain rotation coordinate deformation,with the cavity nucleation,growth and merger,eventually lead to fracture.

关 键 词：搅拌摩擦加工 超塑性 变形行为 应变速率敏感系数 变形机制 晶界滑动 

分 类 号：TG115[金属学及工艺—物理冶金]