Effect of trace Sm elements on microstructure and mechanical properties of TiCp/Al-Cu- Mg-Mn composite materials

Taking TiCp/Al-5Cu-1.9Mg-0.9Mn composite materials reinforced with 0.27%（volume fraction）TiC particles as the matrix， the effects of different Sm element contents on the microstructure and mechanical properties of the composite material were investigated. The results show that the addition of the Sm element significantly refines the dendritic microstructure and facilitates the dissolution of the second phase during the solid solution treatment. Consequently， an increase in the density of precipitated phases， including T-Al20Cu2Mn3 and S'-Al2CuMg， was observed in the aged microstructure. When the Sm element content is high （0.3%， mass fraction， the same below）， the microstructure exhibits blocky insoluble rare earth-containing compounds. With the addition of the Sm， the composite materials show a gradual increase in yield strength at both room temperature and 250 ℃. However， it will cause a decrease in plasticity. When the Sm element content is 0.3%， the yield strength at room temperature increases from 246 MPa to 310 MPa， and the yield strength at 250 ℃ increases from 191 MPa to 220 MPa. The analysis suggests that the increase in strength is attributed to the microstructural refinement and the increased density of precipitated phases induced by Sm. Conversely， the reduction in plasticity is attributed to the presence of coarse blocky insoluble rare earth compounds cutting through the matrix， leading to the easy generation of crack sources.