Hot Deformation Behaviors And Microstructure Of GNPs/Mg Magnesium Matrix Composites

In this paper,0.05%GNPs/Mg?mass fraction?magnesium matrix composite was prepared by low temperature powder metallurgy and hot extrusion.The high temperature compression was tested on Gleeble-3500.The optical microscope?OM?,scanning electronic microscope?SEM?and transmission electronic microscope?TEM?were applied to characterize the microstructure of the GNPs/Mg composite after hot compression and hot rolling.The texture evolution during hot deformation were investigated by X-ray diffraction?XRD?.Instron-5982 was used to measure the tensile properties of the as-rolled GNPs/Mg composite at room temperature.The high temperature compression behaviors of GNPs/Mg composite at different temperatures and strain rates were tested.The results showed that the peak stress decreased with increasing temperature and increased with the increase of strain rate.In present study,it was found that the power law can be applied in this work.The analysis suggest that the deformation mechanism is grain boundary diffusion controls the dislocation climb.The thermal processing map of GNPs/Mg composite is constructed.The optimum hot working domain is the temperature range of 473K-573 K and the strain rate range of 0.001s^-1-0.01s^-1 by the thermal processing map.Microstructure of GNPs/Mg composite after high temperature compression was observed by EBSD.The results showed that the evolution of the microstructure was closely related to deformation temperature and strain rate.Recrystallization mainly occurs in GNPs/Mg composite and the texture type and texture strength were changed after high temperature compression.The effect of the GNPs on the microstructure of the composite is mainly to prevent the dislocations from climbing during the deformation process,which causes the dislocation density around GNPs to increase.Therefore led to increase the recrystallization nucleation rate and refine grains.The tensile strength and yield strength of the composites were 176 and 167 MPa,which 16 and 16 MPa higher than the extruded GNPs/Mg composite.The?0001?basal planes of rolled composite are almost vertical to the extrusion direction indicating that the plate texture is formed during the hot rolling of GNPs/Mg composite.