Ren Yinglei

Effects of Ca on Microstructure and Mechanical Properties of ZA62 Alloys

Effects of Ca element on microstructure and mechanical properties of ZA62 alloys were investigated by using zeiss microscope, scanning electron microscope equipped with an energy dispersive spectrometer, X-ray diffractometer, and electronic universal testing machine. The results show that Ca can significantly refine microstructure and cause the precipitation of Mg2Ca and Al2Ca phases on grain boundary of ZA62 alloys. The addition of Ca can improve the tensile properties of alloys at room temperature. When the content of Ca is 2%, good properties are obtained, the tensile strength and yield strength of Mg-6Zn-2Al-2Ca alloy reaches 240.79MPa and 82.78MPa respectively.

Study on the Hot Tearing Susceptibility of Mg‐7Al‐xCa‐2Si‐0.8Zn‐0.5Sr‐0.4Mn Heat‐resistant Magnesium Alloys

The Mg-7Al-xCa-2Si-0.8Zn-0.5Sr-0.4Mn(x=1,2,3,4wt%) alloys cylindrical specimens were fabricated using the same length metal mold. The hot tearing susceptibility of alloy is evaluated by the Crack-rod critical diameter and hot tearing sensitive coefficient. The optical microscopy, scanning electron microscopy (SEM) and the detector of energy dispersive (EDX) were used to investigate the hot tearing behavior of magnesium alloys. The results indicate that the microstructures of alloys are refined with Ca addition When the Ca content is 3.0%, the crack-rod critical diameter and hot tearing sensitive coefficient are both the lowest, at the same time, the fracture area of α-Mg dendrite is zero and that of eutectic phase is 100%. In the crack formation process, the eutectic phase have the trend of enrichment to crack and the ability to fill in cracks, so the hot tearing susceptibility of alloy is reduced.

Effects of Si on microstructure and mechanical properties of Mg-5Sn-2Sr alloy

Phase constitution and microstructure of the Mg-5Sn-xSi-2Sr (x=0, 1, 2) alloys were analyzed by X-ray diffractometer, optical microscope and scanning electron microscope with an energy dispersive spectrometer. The tensile properties of the alloys were tested by electronic universal testing machine, and the fracture surfaces of the alloys were observed with scanning electron microscope. The results show that the microstructure of the Mg-5Sn-2Sr alloy consists of α-Mg, MgSnSr and Mg2Sn phases. The addition of Si element can promote the formation of Mg2Si phase on the grain boundary, and the content of Mg2Si phase increases with increasing the Si element. Mg2Si is a strengthening phase, which can effectively prevent grain boundary sliding and dislocation motion, and thus, the mechanical properties of the alloys were obviously enhanced. The mechanical properties of Mg-5Sn-2Si-2Sr alloy are better than other alloys, the tensile strength, yield strength, elongation and hardness are 147MPa, 110MPa, 5.0% and 47HB respectively.