Effect Of Different Volume Fractions Of SiCp/2024Al Composite And Short Carbon Fiber Modification On Microstructure And Properties

In this paper,the structural material with mechanical properties as the main performance index is the application background.The research purpose is to prepare composite materials with high tensile strength,high hardness,low thermal expansion coefficient and good dimensional stability.SiCp/2024Al composites with different volume fractions?0%,10%,20%,30%,40%?of SiC particles were prepared by electrothermal powder semi-solid thixoforming method.At the same time,a short carbon fiber modified 20vol%SiCp/2024Al composite was successfully prepared by this method.The interfacial bonding state,fracture morphology,phase composition and distribution of the reinforcing phase in the 2024Al matrix were observed by means of scanning electron microscopy?SEM?and X-ray diffractometry?XRD?;The tensile strength,hardness and thermal expansion coefficient of the composite materials under different preparation parameters were measured by a versatile material testing machine,an electronic Brinell hardness tester,and an electronic thermal expansion instrument.According to the trend of the obtained performance data,the impact mechanism is deeply studied.The research situation and main gains are as follows:?1?The composite material prepared by the electrothermal powder semi-solid thixoforming method has a short preparation period.The semi-solid thixoforming temperature is selected to be 580?,the forming pressure is 40MPa,and the reinforcing phase can be relatively uniformly dispersed in the matrix alloy,and the interface is well bonded.The forming temperature is low,the extrusion time is short,and no impurity phases were detected in the composite material,indicating that the interface didn't appear bad reaction.The prepared composites were treated with T6heat treatment?Solid solution treatment at 505?for 2h,water quenching at room temperature and artificial aging treatment at 180?for 10h?,compared with the fully annealed state,the tensile strength and hardness are significantly improved,the elongation is decreased,the relative density is not affected obviously,and the thermal expansion coefficient is slightly smaller,which provides a feasible preparation method for ceramic particles or fiber reinforced metal matrix composites.?2?When the volume fraction of SiC particles is 20%without adding short carbon fiber,the tensile strength of SiCp/2024Al composite after T6 heat treatment reaches a maximum of 505MPa,compared with the 2024Al tensile strength value of325MPa of the same heat treatment process,increased by 55.4%,the hardness is196HB,the relative density is 97.55%,and the linear expansion coefficient?50¹50??is 11.860×10^-6K^-1,so the comprehensive performance is better;When the volume fraction of SiC particles is 0%,the maximum density and elongation of2024Al after complete annealing are 99.35%and 7.8%;When the volume fraction of SiC particles is 40%,the hardness of SiCp/2024Al composite after T6 heat treatment reaches a maximum value of 244HB,compared with the 2024Al hardness value of144HB of the same heat treatment process,increased by 69.4%,and the linear expansion coefficient?50¹50??reached a minimum value of 9.592×10^-6K^-1.?3?With the increase of the amount of SiC particles added,the silicon carbide particles in the SiCp/2024Al composite exhibit a degree of light to heavy accumulation,and the gap between the particles and the particles becomes more,resulting in a decrease in the density of the composite.At the beginning,the tensile strength increases and next reduces,the elongation reduces,the hardness gradually increases,and the coefficient of thermal expansion reduces.?4?After adding a copper-plated short carbon fiber with a volume fraction of1%,the tensile strength and hardness values of the composites with SiC particle hybrid reinforced 2024Al matrix after T6 heat treatment are 521MPa,210HB respectively,increased by 3.1%and 7.1%after the addition of short carbon fiber in sequence;increased by 2.2%and 10.5%compared with un-coppered short carbon fiber;increased by 60.3%and 45.8%compared with 2024Al,and the relative density and thermal expansion coefficient have reduced.