Research On Fabrication Of Nano-SICp/2024Al Composite Foam And The Compression Of T6 Treatment State

In order to reduce the legal costs of nano SiCp / 2024 Al composites foam fabricated by powder metallurgy and get uniform distribution of foam material porosity and aperture size, this paper uses calcium carbonate as foaming agent and SiC particles as reinforced body to prepare foam composite materials based on the principle of powder densification foaming method. The paper study the effect of foaming process and solution aging on the properties of foam composite material compression and energy absorption by improving preparation technology of foaming precast body. The microstructure of composite powder and foaming precast body were observed by SEM. The distribution uniformity of the SiC nanoparticles and CaCO₃ powder were analyzed by EDS. Foam precast body was prepared by cold pressing hot extrusion process. The thermal decomposition of foaming agent CaCO₃ and heat matching characteristics of foaming agent and foam precast body of matrix alloys were studied by using differential thermal analysis（DTA）. Foaming precast body density and analysis the feasibility of cold hot extrusion process were measured by the drainage method and the optimum process parameters were obtained by research the effect of foaming temperature, time, content of SiC nanoparticles on the foam porosity, average pore diameter and porosity distribution. The nona-peak aging time of SiCp/2024 Al is determined via XRD phase analysis, vickers hardness measurement after processing solid solution and aging treatment to foaming precursor. Using gleeble 1500 thermal simulation testing machine to study the effect of solid solution aging treatment, porosity, SiC content on the foam composite quasi static compression energy absorption performance.High energy ball milling process parameters: milling speed of 180 rpm, milling time of 6h, ball-to-powder weight ratio of 10:1. Mechanical milling process parameters: milling time of 6h, ball-to-powder weight ratio of 5:1. Through the above two ways, relatively uniformly composite powder of SiC enhancers and foaming agent CaCO₃ can be obtained. Cold pressure of 260 MPa, holding time 20 min.After cold pressing and hot extrusion, extrusion temperature of 500 ℃, holding time of 45 min, extrusion ratio of 16:1. Hot extrusion promotes the flowing of reinforcement SiC and foaming agent in the matrix 2024 Al, making more uniform distribution in the matrix. If the foaming time is constant, the higher of foaming temperature, the larger of pore size and porosity. If the foaming temperature is constant, the longer of foaming time, the greater of the pore size. The porosity is increased first and then decreased. Nano SiC particles not only can greatly improve the strength of the matrix, but also significantly increased the viscosity of molten aluminum, making the passage of the gas-liquid interface resistance increasing. At the same foaming temperature and time, as the volume fraction of SiC particles increases, the porosity of the foam and the average pore size is reduced.In the process of quasi static compression, the deformation of foam composite material has obvious three stages: elastic deformation stage, yield platform stage and densification stage. Solid solution aging treatment can improve the strength, stress and energy absorption per unit volume of foam composite material yield. But the influence on the peak value of energy absorption efficiency is little. As the porosity increases, foam compression yield strength decrease, the length of the compression yield increase, the absorption of unit volume reduce, absorption ability drop and the peak of energy absorption efficiency increase. The volume fraction of SiC increase. As the volume fraction of SiC increases, the compress yield strength of foam composites improve, the length of the yielding platform change little,the unit volume of absorption energy become higher and the energy absorption capacity increase. But the influence on the peak energy absorption efficiency is little.In the experiment of damping performance, damping strain spectrum of foam composites show typical dislocation damping characteristics. After solid solution aging treatment,damping value is smaller and change little when strain amplitude is small. When strain amplitude is more than the critical strain amplitude, three aging state damping value increased rapidly with the increase of strain amplitude. The damping values of short aging state is fastest-growing, peak aging is little slower and underaged is slowest.With the increase of porosity, damping performance of foam composite at room temperature become lower.