Effects of Li content on microstructure and mechanical properties of as-cast Mg-xLi-3Al-2Zn-0.5Y alloys  

Li含量对铸态Mg-xLi-3Al-2Zn-0.5Y合金微观组织与力学性能的影响

作　　者：Xiang PENG Wen-cai LIU Guo-hua WU 彭翔;刘文才;吴国华(上海交通大学材料科学与工程学院轻合金精密成型国家工程中心和金属基复合材料国家重点实验室,上海200240)

机构地区：[1]National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composite,School of Materials Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China

出　　处：《Transactions of Nonferrous Metals Society of China》2022年第3期838-849,共12页中国有色金属学报（英文版）

基　　金：financially supported by the National Natural Science Foundation of China (Nos.51821001, U2037601);Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment (No. SKL2020005)。

摘　　要：The effects of Li content on the microstructure and mechanical properties of the as-cast Mg−xLi−3Al−2Zn−0.5Y(LAZx32-0.5Y)alloys were investigated by XRD,SEM,TEM,hardness tester and universal testing machine.The results show that the matrix of the alloy transforms fromα-Mg toα-Mg+β-Li and then toβ-Li when the Li content increases from 4%to 14%(mass fraction).All LAZx32-0.5Y alloys contain AlLi and Al_(2)Y,while MgLi_(2)Al appears only in the alloy containing theβ-Li matrix.As the Li content increases,the content of AlLi and MgLi_(2)Al gradually increases,while the content of Al_(2)Y does not change much.As the Li content increases from 4%to 10%,the ultimate tensile strength and hardness of the as-cast LAZx32-0.5Y alloys gradually decrease while the elongation gradually increases.The corresponding fracture mechanism changes from cleavage fracture to quasi-cleavage fracture and then to microporous aggregation fracture.This is mainly attributed to the decrease ofα-Mg and the increase ofβ-Li in the alloy.When the Li content continues to increase to 10%and 14%,the yield strength,ultimate tensile strength and hardness of the as-cast LAZx32-0.5Y alloys gradually increase,while the elongation decreases sharply,which is mainly attributed to the nano-scale MgLi_(2)Al uniformly distributed in theβ-Li matrix.通过XRD、SEM、TEM等微观表征和力学性能测试,研究Li含量对铸态Mg−xLi−3Al−2Zn−0.5Y(LAZx32-0.5Y)合金微观组织与力学性能的影响。结果表明:当Li含量从4%增加14%(质量分数)时,合金的基体相由α-Mg单相转变为α-Mg+β-Li双相再转变为β-Li单相。所有合金中都含有AlLi相和Al_(2)Y相,而MgLi_(2)Al相只出现在含有β-Li基体的合金中。随着Li含量的增加,AlLi相和MgLi_(2)Al相的含量逐渐增多,而Al_(2)Y相的含量变化不大。当Li含量从4%增加至10%时,铸态LAZx32-0.5Y合金的抗拉强度和硬度逐渐降低而伸长率逐渐增加,对应的断裂机理由解理断裂转变为准解理断裂再到微孔聚集型断裂,这主要归因于合金中α-Mg基体逐渐减少而β-Li基体逐渐增多。当Li含量继续增加至10%和14%时,铸态LAZx32-0.5Y合金的屈服强度、抗拉强度和硬度逐渐增加而伸长率则急剧下降,这主要归因于β-Li基体中弥散分布的纳米级MgLi_(2)Al相。

关 键 词：Mg-Li alloy li content ALLOYING microstructure mechanical properties 

分 类 号：TG146.22[一般工业技术—材料科学与工程]