Effect Of Trace Sb Addition On Microstructure And Mechanical Properties Of Mg-2.7Nd-0.4Zn-0.5Zr Alloy

Heat resistant magnesium alloys are generally rare earth magnesium alloyswith high amounts of rare earth, which have wide applications in the automotiveindustry, defense industry, aviation, aerospace and other fields. Mg-Nd-Zn-Zrmagnesium alloy is a kind of cast magnesium alloy, usually termed as"Mg-RE-Zr alloys". As a kind of high-strength heat-resistant magnesium alloys,with the main alloying element being neodymium, it has good casting properties,low sectional sensitivity and micro porosity. At the same time, it has good roomtemperature and high temperature performance. So far, the researchon Mg-Nd-Zn-Zr magnesium alloy is mainly concentrated on the effect of rareearth elements (such as Nd, Y, Ce, La), Zn and extrusion process on themicrostructure and properties of the alloy. Based on high-strength heat-resistantmagnesium alloy, such as Mg-2.7Nd-0.4Zn-0.5Zr, this paper adds trace Sb anduses new heat treatment process to improve the performance of this alloy. Theeffect of Sb elements on the microstructure and properties of the alloy is studiedand the content of element Sb is optimized.This paper systematically studied the effect of trace Sb addition onmicrostructure and mechanical properties of Mg-2.7Nd-0.4Zn-0.5Zr-xSb alloys.The strengthening mechanism of Sb elements on the the material is revealed bymeans of X-ray phase analysis (XRD), optical microscopy (OM), scanningelectron microscopy (SEM), EDS spectroscopy, transmission electronmicroscopy (TEM), hardness testing and room temperature tensile test et alanalysis methods. Due to the formation Mg3Sb2phase, the present experimentalresults showed that adding small amounts of Sb to Mg-2.7Nd-0.4Zn-0.5Zr-xSballoys with Zr can produce the following effects:(i) the refined grain size of as-casted alloys, and the grain growth of solutionized and aged alloys inhibited;the morphology, size and distribution of casting divorced eutectic alloy phaseMg12Nd modified.(ii) the addition of trace Sb could significantly improve thehardness, strength and plasticity of the microstructure at as-cast state, solidstate, aging state.(iii) under different heat treatment conditions, with increasingthe content of Sb element, the grains become finer; the hardness isbasically increasing continuously; the strength and the plasticity is increasedfirst and then decreased.(iv) basically, all properties reached the maximumvalue in the vicinity of the0.08wt%Sb. The minimum average grain size of thealloy under different heat treatment was13.9um (as-casted),35.7um (solidsolution state) and37.1um (aged), respectively. The maximum Brinell hardnesswas67.7(as-casted),65.1(solid state) and89.5(aged state), respectively. Themaximum tensile strength was184MPa (as-casted),198MPa (solid state) and275MPa (aged state), respectively. The maximum yield strength was117MPa(as-casted),112.7MPa (solid state) and205.5MPa (aged state), respectively.The maximum elongation rate was11.1%(as-casted),23.5%(solid state) and9.1%(aged state), respectively. The largest reduction percentage of area was11.2%(as-casted),20.1%(solid state) and9.5%(aged state), respectively.Strengthening effect of alloying elements Sb on the magnesium alloys ismainly through the grain refinement mechanism.Alloying element Sb has little effect on the fracture mode of the material.Under different heat treatment conditions, it mainly presents the intergranularfracture (as-casted), transgranular quasi-cleavage fracture (solid state) andtransgranular cleavage fracture, respectively.Based on the comprehensive analyses of the experiments, the optimizedaddition of Sb is0.08wt%to Mg-2.7Nd-0.4Zn-0.5Zr alloy.