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为了研究Mg-Gd-Zn-Zr合金中的长周期堆垛有序(LPSO)结构的形成及其演化,对铸态、固溶态和时效态Mg_(96.32)Gd_(2.50)Zn_(1.00)Zr_(0.18)合金的显微组织进行了观察.OM,SEM和TEM观察表明,合金铸态组织由α-Mg固溶体、晶内层片状14H-LPSO结构和晶界处树枝状α-Mg+β-(Mg,Zn)_3Gd共晶相组成;500℃/35 h固溶处理后,晶界处发生β→X的固态相变,层片状X相也具有14H-LPSO结构;再经200℃/128 h峰时效处理后,晶内析出椭球状β′相和片状β_1相与14H-LPSO结构共存.室温拉伸实验和Vickers硬度测试表明,500℃/35 h+200℃/128 h处理改善了合金的力学性能,抗拉强度为290.7 MPa,屈服强度为162.5 MPa,Vickers硬度为108.0 HV,延伸率为10.4%.力学性能的改善与晶界、晶内的14H-LPSO结构及时效相等复合强韧化作用有关.
In order to study the formation and evolution of long period stacking ordered (LPSO) structures in Mg-Gd-Zn-Zr alloys, the microstructures of as-cast, solid solution and aged Mg_ (96.32) Gd_ (2.50) Zn_ (1.00) The microstructure of Zr_ (0.18) alloy was observed by OM, SEM and TEM.The results show that the as-cast microstructure of the alloy consists of α-Mg solid solution, 14H-LPSO lamellar structure and dendritic α-Mg + After solid solution treatment at 500 ℃ for 35 h, the solid state transformation of β → X occurs in the grain boundary, and the lamellar X phase also has a 14H-LPSO structure. After 200 After the aging treatment at ℃ / 128 h, the precipitated ellipsoidal β ’phase and the β_1 phase coexist with the 14H-LPSO structure.The results of tensile test at room temperature and Vickers hardness show that at 500 ℃ / 35 h + 200 ℃ / 128 h The mechanical properties of the alloy were improved with the tensile strength of 290.7 MPa, the yield strength of 162.5 MPa, the Vickers hardness of 108.0 HV and the elongation of 10.4% .The mechanical properties were improved with the grain boundary and intragranular 14H-LPSO structure and aging Equivalent composite toughening effect.