Investigation of mechanical properties, microstructure and corrosion AZ31 alloy in cyclic closed-die forging (CCDF)
Abstract:
Today, for progress in industries such as automotive, aerospace and medicine, knowledge and development of materials is very necessary. Nanocomposites are one of the most important categories of metal-based composites, which have always received attention due to having some special properties. Magnesium-based composites are one of the metal-based composites whose applications have been developed in recent years. Magnesium and its alloys have desirable properties such as light weight, good strength and biocompatibility. Adding reinforcing particles to magnesium fields improves some mechanical properties such as hardness and strength. Graphene reinforcement nanoparticles, which are from the family of ceramic and carbon reinforcements, have received much attention. In order to use magnesium and its alloys more, their physical and mechanical properties should be improved. The use of severe plastic deformation (SPD) processes greatly changes the microstructure of the material and improves some mechanical properties in the material. The present research was conducted in order to improve the mechanical properties of AZ31 magnesium alloy, in which a composite reinforced with graphene nanoplates (GNPs) and reduced graphene oxide nanoplates (RGO) was made using traditional sintering and spark plasma sintering (SPS) methods and finally it was subjected to closed mold forging process at room temperature. In the following, the mechanical properties, including final strength and hardness, were investigated using tensile test and microhardness test. In addition, the microstructure of the material was investigated using field emission scanning electron microscope (FE-SEM) equipped with EDX, optical microscope (OM) and X-ray diffraction (XRD). By performing one pass of the process, the microstructure was modified and a more homogeneous structure was observed. The results showed a 31% increase in hardness from 400 Vickers to 524 Vickers in the samples reinforced with graphene nanoparticles compared to the pure sample. In addition, the final strength was associated with a 13% increase, so that it increased from 128 MPa in the pure sample to 144.5 MPa in the sample reinforced with graphene nanoparticles. Also, the grain size decreased from 114 µm to 31 µm.