As-cast Microstructures and Mechanical Properties of Mg-5Y-2Nd-xSm-0.5Zr (x= 0, 1, 3, 5) Magnesium Alloys

Abstract

The microstructures and mechanical properties of the as-cast Mg-5Y-2Nd-xSm-0.5Zr (x= 0, 1, 3, 5) alloys have been investigated by optical microscope (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) analysis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and mechanical tensile test. The results show that all the as-cast alloys are mainly composed of α-Mg, Mg24Y5 and Mg41Nd5. After adding Sm, the alloy has a new phase of Mg41Sm5. Furthermore, grain gets refinement, the second phases gradually increase and the morphology of second phases transforms to continuous network distribution. In addition, the mechanical properties of the as-cast alloys vary with Sm content. With the increase of Sm, the ultimate tensile strength, yield strength and hardness of the alloy increase firstly and then decrease, and the elongation decreases. When the amount of Sm is 3%, the alloy has the best mechanical properties, and the ultimate tensile strength, yield strength, hardness and elongation are 245.9 MPa, 207.6 MPa, HV85.9 and 5.88%, respectively. The Mg-5Y-2Nd-0.5Zr alloy to which Sm is not added has a mixed fracture characteristic of ductile fracture and local cleavage fracture. In comparison, when the Sm is 3%, the tear surface of the fracture surface is fine and uniform, and there is no obvious secondary crack and a large dissociation surface, indicating that the fracture energy absorbs more energy, so it shows a high fracture. Strength and high elongation.