The Microstructure And Properties Of Mg-Sn Based Alloys Were Controlled By The Second Phase

Magnesium and its alloys have broad application prospects in the fields of automobile,aerospace,electronic communication and national defense,and are honored as"the most developed green engineering materials in the 21st century".Mg-Sn series alloys have great potential in developing high-strength and tough-deformation magnesium alloys due to their good deformation properties and excellent precipitation strengthening effect due to the presence of Mg₂Sn phase?1043 K?,which leads to the comprehensive performance better than that of the traditional Mg-Al and Mg-Zn alloy systems.In addition,on the basis of Mg-Sn base alloy,the addition of appropriate proportion of Zn and Al elements will induce the formation of Mg-Zn-Al quasicrystalline phase and refine Mg₂Sn phase.At the same time,Al element will also play a solid solution strengthening role,thus greatly improving the comprehensive tensile properties and thermal stability of Mg-Sn series alloy and providing a feasibility for the development of heat-resistant magnesium alloy without rare earth.In addition,in order to develop sustainable materials and alleviate the resource dependence of material development,the development of low-alloying magnesium alloys has attracted more and more attention.In order to explore the high strength and toughness mg-sn-based low-alloying magnesium alloy,Ca and Mn were used to regulate the microstructure of low-alloying mg-sn-based magnesium alloy in this paper.It is expected that the addition of Mn and Ca elements can change the texture,refine the microstructure,and improve the plasticity and deformation capacity of the alloy.Therefore,the aging strengthening behavior of Mg-8Sn-6Zn-2Al?TZA862?alloy containing quasicrystalline phase was studied.Meanwhile,in order to develop low-alloying Mg-Sn base alloys,the effects of different extrusion ratios and Sn contents on the microstructure and properties of Mg-Sn-Mn-Ca low-alloying alloys were studied.The research results show that:?1?The study found that the double aging after 168 h,Mg-8Sn-6Zn-2Al alloy's hardness increased to a peak of 87 HV,double aging treatment on the alloy grain size,precipitation phase orientation and precipitated phase volume fraction and the properties of texture has a great influence,which resulted in increased grain size,precipitation phase volume fraction increased?grain boundary nucleation?,texture orientation and intensity change.?2?The peak-aged Mg-8Sn-6Zn-2Al alloy has a high strength?257 MPa?and a reasonable elongation rate?13.6%?,which is mainly related to the nano-sized precipitated phase and a reasonable machining hardening index.?3?The extruded low alloying Mg-Sn-Mn-Ca alloy series?with extrusion ratio of 36?exhibited complete dynamic recrystallization and ED-tilted texture.With the increase of Sn content from 0.5 to 1.0 wt.%,the average grain size decreased from 13.6 to 12.25?m,and the texture strength increased from 5.82 to9.23.In addition,some nano-meter and/or sub-micron sized precipitated phases of Mg₂Sn and Mg₂Ca can be detected in some micro-regions,and the morphology shows that Mg₂Sn is adjacent to Mg₂Ca.?4?The Meyer index n of the extruded Mg-Sn-Mn-Ca alloy?with extrusion ratio of 36?series are less than 2,indicating a strong indentation size effect.The extruded TMX-1.0 alloy exhibited good comprehensive mechanical properties,which were mainly attributed to smaller grain size,higher ED-tilted texture intensity and reasonable machining hardening index.?5?When the extrusion ratio decreases from 36 to 16,the Mg-Sn-Mn-Ca alloy system exhibits uniformly refined dynamic recrystallized grains and coarser non-dynamic recrystallized grains coexisting along the extrusion direction.The average grain size decreases from 13.60?m?0.5Sn?and 12.25?m?1.0Sn?to 7.8?m?0.5Sn?and 7.1?m?1.0Sn?,and the tensile strength and elongation decreases year on year.The mechanical properties of weak alloys are mainly related to the appearance of coarse non-dynamic recrystallized grains in the structure.?6?When the extrusion ratio decreases from 36 to 16,the Meyer index n of as-extruded alloys increases from 1.74?0.5Sn?and 1.84?1.0Sn?to 1.86?0.5Sn?and 1.89?1.0Sn?,respectively.It is shown that the large extrusion ratio can enhance the indentation size effect of the alloy system.