Study On Hot Deformation Behaviors And Microstructure Evolution Of C_sf/AZ91D Composites Fabricated By Vacuum Pressure Infiltration Method

Magnesium alloy has the advantages of low density, high specific strength, high specific stiffness, good damping capacity and electromagnetic shielding properties.However,as a structural material, its engineering application was limited by its low elastic modulus, hardness and wear resistance. The appearance of Magnesium matrix composites made up for the deficiency of magnesium alloys, and the high performance carbon fiber reinforced magnesium alloy composite material is gradually becoming a kind of magnesium composites in aerospace, automotive and electronic industries with the most promising because of its high strength, high modulus, high wear resistance and low thermal expansion coefficient, excellent performance.Especially the chopped carbon fibers reinforced magnesium composites with low preparation cost, mechanical properties of isotropic and can secondary processing and other advantages, have become an important research direction of the magnesium based composite material. In order to obtain the magnesium matrix composite structure, the structure of the magnesium matrix composite was generally required to be formed by two times, because of the poor ductility and plastic deformation ability of the carbon fiber reinforced magnesium matrix composites, it has brought great difficulties to the production and application of the parts.. Therefore, in order to improve the chopped carbon fiber reinforced magnesium matrix composite plastic forming ability, it is necessary to carry out the research on the high temperature plastic deformation behavior and its deformation mechanism.This article has carried on the research in the following several aspects:Chopped carbon fiber perform with excellent performance was prepared by wet process. Taking into account the magnesium alloy under the liquid flammable, easy evaporation characteristics, the magnesium alloy melting protection device was designed and developed., Chopped carbon fiber reinforced magnesium matrix composites i.e. C_sf/AZ91 D composite with a volume fraction of 15% were prepared by vacuum pressure infiltration method, it not only provide the basis for subsequent compression test, but also provide the experiment reference for the further optimization of the preparation process parameters of C_sf/AZ91 D composites.The high temperature plastic deformation behavior of C_sf/AZ91 D composite atthe initial melting point temperature was studied by means of isothermal compression tests. According to the experiment results, the dependence of flow stress on deformation temperature, deformation degree and strain rate was quantificationally analyzed. Based on the comparison of plastic deformation behavior of magnesium alloy, the strain softening mechanism of C_sf/AZ91 D composite was analyzed. By calculating the strain rate sensitivity exponent and apparent deformation activation energy of C_sf/AZ91 D composites, the difference of the plastic deformation mechanism of the composite and the magnesium alloy was analyzed. According to the compression deformation behavior of C_sf/AZ91 D composites under high temperature,high temperature stress mechanical constitutive equation was established; the flow behaviors of C_sf/AZ91 D composites under different deformation conditions can be predicted accurately by the test. It provided the theoretical model for further research on C_sf/AZ91 D composites in high temperature plastic deformation plastic flow rule.Through the organization structure before and after deformation of C_sf/AZ91 D composite material analysis, this study found that chopped carbon fiber in high temperature compression process has obvious deflection and partial broken phenomenon, the effect of short carbon fiber on the dynamic recrystallization behavior of the matrix is analyzed.. The average size of the grain size of matrix alloy under different deformation conditions is measured by Image-Pro Plus image processing software., this study found that the dynamic recrystallization grain size of matrix alloy decreases with the decrease of the deformation temperature and the strain rate increases. This study provides an experimental basis for the follow-up study and the establishment of the constitutive model for dynamic recrystallization of C_sf/AZ91 D composites.The research results provide a theoretical reference for understanding the mechanical behavior and microstructure evolution of C_sf/AZ91 D composites at high temperature plastic deformation, meanwhile, it probably has some common reference value for investigation on the hot plastic forming technology of the discontinuous reinforced metal matrix composites.