Effect of Ca and Sm Combined Addition on the Microstructure and Elevated-Temperature Mechanical Properties of Mg-6Al Alloys

Abstract

In the present study, the microstructure and elevated-temperature mechanical properties of Mg-6Al, Mg-6Al-4Ca, Mg-6Al-4Sm and Mg-6Al-2Ca-2Sm alloys were investigated. The experimental results showed that the microstructure and elevated-temperature mechanical property of Mg-6Al alloy changed obviously with the different elements addition. By analyzing the results of optical microscope, x-ray diffraction analysis, scanning electron microscope, and transmission electron microscope, it could be determined that there was only Mg17Al12 phase in Mg-6Al alloy, there were Al2Ca and (Mg, Al)2Ca phases in Mg-6Al-4Ca alloy, there were Al2Sm and Mg17Al12 phases in Mg-6Al-4Sm alloy, and there were (Mg, Al)2Ca, Al2Ca and Al2Sm phases in Mg-6Al-2Ca-2Sm alloy. In addition, the addition of alloying elements including Ca and Sm, especially the composite addition, could significantly improve the tensile properties of Mg-6Al alloy. Compared to Mg-6Al alloy, the tensile strengths of Mg-6Al-2Ca-2Sm alloy at 448, 473 and 498 K were enhanced by 50.32, 87.92, and 94.99%, respectively. Furthermore, when the stretching temperatures were 448 and 473 K, the fracture pattern of Mg-6Al-2Ca-2Sm alloy was the mixture of intergranular fracture and trans-crystalline fracture. However, when the stretching temperature was 498 K, the fracture pattern of Mg-6Al-2Ca-2Sm alloy was the intergranular fracture.