The microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys

Abstract

Optical microscopy, scanning electron microscopy, X-ray diffraction and tensile testing were performed to investigate the microstructure and mechanical properties of as-cast Mg–4Y/Nd–2Zn alloys. The results show that the secondary dendritic arm spacing for the Mg–4Y–2Zn alloy is smaller than that for the Mg–4Nd–2Zn alloy, and that X-Mg12YZn or W-Mg3Zn3Nd2 form in Mg–4Y/Nd–2Zn alloys. The lamellar X phase distributes at the grain boundary, pointing into the grains, whereas the rod-like W phase preferentially segregates at the triangle junction of the grain boundary. The greater grain boundary strengthening effect and the smaller fragmentation effect of the brittle eutectic phases leads to the as-cast Mg–4Y–2Zn alloy having better comprehensive mechanical properties. The fracture mechanism for as-cast Mg–4Y/Nd–2Zn alloys is quasi-cleavage fracture.