固溶温度对Mg-2Gd-2Zn轧制板材显微组织和力学性能的影响

摘要

采用OM、SEM、EDS、XRD、显微硬度计和力学试验机研究了400℃、430℃、460℃、490℃和520℃不同固溶温度对轧制态Mg-2Gd-2Zn舍金板材组织结构和力学性能的影响.结果表明,当温度不高于490℃时,晶粒尺寸随固溶温度升高几乎呈线性增长趋势.第二相颗粒也随固溶温度升高总体呈减少趋势.但在490℃固溶温度下,第二相反而增加,且呈细小弥散分布.此时显微硬度达最大值,为77.88HV,固溶时效强化效果显著.XRD分析结果表明,当固溶温度从430℃升高到490℃时,第二相主要由MgZn2和GdZn5的初生相转变为MgZn2和GdZn的沉淀相.490℃固溶处理下合金板材沿RD、TD和45°方向的抗拉强度均达到最大值,分别为262 MPa、244MPa和254MPa;断裂伸长率略有降低,分别为34％、31％和39％,但塑性各向异性降低.%Different solution treatments at 400 ℃,430 ℃,460 ℃,490 ℃ and 520 ℃ were carried out on the rolled Mg-2Gd-2Zn alloy sheets under the same solution time of 0.5 h and aging treatment of 225 ℃ × 12 h.The effects of solution temperature on the microstructure,phases composition and mechanical properties of the alloy sheets were investigated by OM,SEM,EDS,XRD,micro-hardness and mechanical tester.Below 490 ℃,the grain size increased linearly and the number of the second phase particles decreased with the increasing solution temperature.Whereas the second phase particles suddenly increased and presented dispersed distribution at 490 ℃,which resulted in the highest micro-hardness of 77.88HV.XRD results show that the compositions of second phases have transformed from the primary phase of MgZn2 and GdZn5 at 430 ℃ to the precipitated phase of MgZn2 and GdZn at 490 ℃.Therefore,under 490 ℃,the Mg-2Gd-2Zn alloy sheets present good mechanical properties with the highest tensile strength of 262 MPa,244 MPa and 254 MPa along the direction of RD,TD and 45°,and elongation of 34％,31％ and 39％ with low ductility anisotropy,respectively.