均匀化工艺对高速列车用Al-Mg-Si合金组织与力学性能的影响OA

The effects of different homogenization processes on the microstructure and mechanical properties of high-strength Al-Mg-Si alloys for high-speed trains were investigated using scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results indicate that homogenization effectively eliminates dendritic segregation in the as-cast microstructure,improves compositional uniformity,and promotes dissolution of non-equilibrium phases at grain boundaries.One-step homogenization at 550℃/10 h reduces the area fraction of α-Al(FeMn)Si crystalline phases from 1.86%in the as-cast state to 0.93%.Compared with one-step homogenization,three-step homogenization at 300℃/4 h+420℃/6 h+550℃/8 h significantly promotes precipitation of nanoscale α-Al(FeMn)Si dispersoids,increasing their area fraction from 0.90%to 2.08%.However,homogenization reduces the number of particles stimulating recrystallization nucleation,and Al3Zr dispersoids fail to precipitate effectively,resulting in severe grain coarsening in the T6 state,the one-step homogenized sample exhibits the largest grain size of 307.0 μm.Furthermore,homogenization adversely affects the strength of the T6-treated alloy.The tensile strength of homogenized alloys decreases by 39.0-46.8 MPa compared with the non-homogenized specimen,which achieves 393.3 MPa and an elongation of 13.5%in the T6 temper,demonstrating a good strength-ductility balance.Ductility improves with increasing homogenization steps,and the elongation reaches 15.3%after three-step homogenization.