Fang Daqing

Microstructure and Mechanical Properties of Extruded Mg-Sm-Ca Alloys

Abstract Microstructure, age hardening response and mechanical properties of Mg-4.0Sm-xCa (x=0.5, 1.0, 1.5, wt%) alloys extruded followed by isothermal aging at 200 oC were investigated. The results indicate that with the addition of Ca, the bulk and particle-like Mg41Sm5 phase containing Ca and the needle/rod-like Mg2Ca phase are formed in the Mg matrix, grains of the alloy are refined and tensile mechanical properties are improved remarkably. Under T5 (peak-aging) condition, the Mg-4.0Sm-1.0Ca alloy shows the smallest grain size of 5.1 μm. With the increase of Ca content the amount of Mg2Ca phase increases gradually, but that of the bulk Ca-containing Mg41Sm5 phase, which is mainly distributed at the grain boundaries, decreases obviously when Ca content reaches 1.5 wt%. The peak-aged Mg-4.0Sm-1.0Ca alloy exhibits the highest hardness HV (820 MPa) and the optimal ultimate tensile strength, yield tensile strength and elongation of 267 MPa, 189 MPa and 24%, respectively. The improved mechanical properties of the alloy are attributed to the grain refinement, the solution strengthening and the precipitation strengthening of Mg2Ca phase and Mg41Sm5 phase.

Effects of Heat Treatment on Microstructure and Mechanical Properties of as-Extruded Mg-9Sn-1.5Y-0.4Zr Magnesium Alloy

Abstract The effects of heat treatment on microstructure and mechanical properties of the as-extruded Mg-9Sn-1.5Y-0.4Zr (wt%) alloy were investigated experimentally. The results show that the heat treatment plays an important role on the microstructure and mechanical properties of the as-extruded Mg-9Sn-1.5Y-0.4Zr alloy. The as-extruded alloy is mainly composed of non-uniform Mg 2 Sn phase. After the solution treatment at 495 °C for 10 h, a majority of Mg 2 Sn phases in the alloy dissolve into the matrix. Aging treatment can highly improve the mechanical properties of the Mg-9Sn-1.5Y-0.4Zr alloy. The optimized experimental condition is aging at 250 °C for 60 h after solution treatment at 495 °C for 10 h. The corresponding mechanical property parameters are: hardness HV of 890 MPa, ultimate tensile strength of 262 MPa, yield strength of 218 MPa, and elongation of 10.4%. Based on the experimental analysis, we find that the precipitation strengthening is the main contributor (∼51.76%) to the total yield strength in the aged experimental alloy.