摘要
用搅拌摩擦加工(FSP)技术制备3种不同Cu含量的Mg-8Zn-xCu合金(x=0,0.5,1,质量分数,%)并使用差热分析法和背散射电子成像等手段对其表征,研究了Cu含量对其性能的影响。结果表明,随着Cu含量的提高Mg-8Zn合金的凝固共晶相由346℃低熔点二元共晶向434℃高熔点三元共晶转变,主要共晶化合物由Mg_(7)Zn_(3)相转变为MgZnCu相,共晶温度的提高抑制了FSP过程中的共晶熔化开裂。Cu含量为0.5%的合金,搅拌摩擦热-力耦合作用使加工区中大部分粗大第二相固溶于镁基体,使Zn元素的固溶量高达6.62%(质量分数),约为室温平衡固溶度的4倍。与FSP Mg-8Zn合金相比,FSP Mg-8Zn-0.5Cu合金的抗拉强度(提高50 MPa)达到了300 MPa,断裂伸长率从13.4%显著提高到30.2%。产生这一优异的强韧化效果的原因是组织均匀性的提高、高含量Zn的固溶强化、晶粒细化以及MgZn_(2)动态沉淀相的协同作用。Cu含量提高到1%使未固溶的第二相在加工区呈带状偏聚,导致合金的拉伸性能显著降低。
Three Mg-8Zn-xCu(x=0,0.5 and 1,mass fraction,%)alloys were prepared by friction stir processing(FSP).Meanwhile,the influence of Cu content on the formability and mechanical proper-ties of FSP Mg-8Zn alloys at high rotation rate was investigated by differential thermal analysis(DTA)and backscattered electron(BSE)etc.It was found that with the increasing Cu content,the eutectic in the Mg-8Zn-xCu alloys was transformed from a low-melting-point binary eutectic(346℃)to a high-melting-point ternary eutectic(434℃)during solidification process.The predominant eutectic phase was evolved from the Mg_(7)Zn_(3) to the MgZnCu phase.The elevated eutectic temperature effectively suppressed the li-quation(i.e.,liquid formation)and liquation-induced cracking during FSP.By a Cu content of 0.5%,most of the secondary phases were dissolved into the Mg matrix via the thermo-mechanical coupling effect of FSP.This resulted in a super high Zn solid solution content of 6.62%(mass fraction)in Mg matrix,approx-imately 4 times of the room-temperature equilibrium solubility.Compared with the FSP Mg-8Zn alloy,the FSP Mg-8Zn-0.5Cu alloy exhibits a 50 MPa increase in tensile strength,achieving 300 MPa,and the elon-gation to fracture significantly increases from 13.4%to 30.2%.It is the improvement of microstructural uni-formity that leads to a simultaneous enhancement of strength and ductility,supplemented by the synergis-tic action of high-content Zn solid solution strengthening,grain refinement,and MgZn_(2) dynamic precipita-tion strengthening.As the Cu content was increased to 1%,stripe-like particle clusters formed within the processing zone due to the undissolved secondary phases,leading to a significant degradation in tensile properties.
作者
戴衡霞
董旭光
薛鹏
倪丁瑞
马宗义
DAI Hengxia;DONG Xuguang;XUE Peng;NI Dingrui;Ma Zongyi(School of Materials Science and Engineering,Shenyang Ligong University,Shenyang 110159,China;Shi-changxu Innovation Center for Advanced Materials,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China)
出处
《材料研究学报》
北大核心
2025年第11期813-823,共11页
Chinese Journal of Materials Research
基金
国家自然科学基金(52071317)
沈阳市U40杰出青年基金(RC230864)。
关键词
金属材料
高锌镁合金
搅拌摩擦加工
热裂
共晶
固溶
metallic materials
high-zinc magnesium alloy
friction stir processing
liquation-induced cracking
eutectic
solid solution
