Study On Preparation And Welding Of Particle Reinforced Al-Mg Alloy

Aluminum alloy is a common lightweight material due to its low density,which plays a key role in military and civil construction.At present,the high requirements for environment and energy lead to the many new challenges of aluminum alloy.Normal aluminum alloy cannot fully meet the requirements.To solve the problem,many researches turn to aluminum matrix composites,where reinforcements are added into the aluminum matrix.The addition improves the stiffness,specific strength,wear,creep and fatigue properties compared to the conventional engineering materials.In this paper,ceramic particles reinforced Al-5Mg composites were successfully prepared by semi-solid stirring assisted ultrasonic casting.By means of metallographic microscope,scanning electron microscope,universal tensile testing machine,friction and wear testing machine,and further rolling and welding tests of materials,the mechanical properties of materials were studied.The main conclusions are as follows:?1?The reinforcing particles mainly distribute along the grain boundary.The particles effectively promote the nucleation rate of alpha-Al during cooling and solidification process,hinder the grain growth,and refine the grain size of the material.The average grain sizes of Al-5Mg alloy,3wt%SiC_p/Al-5Mg,3wt%WC_p/Al-5Mg and 3wt%Ti₁₀C₇N_3p/Al-5Mg composites are 230,114,62 and 60?m,respectively.The incorporation of different particles can improve the mechanical properties of the composites.The tensile strength of 3wt%SiC_p/Al-5Mg,3wt%WC_p/Al-5Mg and 3wt%Ti₁₀C₇N_3p/Al-5Mg composites was increased by75.87%,78.86%and 80.53%,respectively,compared with that of Al-5Mg matrix alloy??2?The electrochemical corrosion test showed that the composite materials favored to self-corrosion.However,Ti₁₀C₇N_3p/Al-5Mg has a low corrosion current density,indicating that the corrosion rate of the composite is lower.?3?The 3wt%SiCp/Al-5Mg composite welding wire was prepared and the welding parameters of 7075-T651 aluminum alloy were optimized.The optimum process parameters are as follows:I=180A??=60°?v=12L·min^-1 and f=M40Hz.With the optimized welding process parameters,a tungsten inert gas welding of aluminum alloy 7075 in the butt joint were performed.The 3wt%SiCp/Al-5Mg composite welding wire can increase the yield,tensile strength and elongation of welding joint by 13%,8%and 19%,respectively.However,for the 3wt%Ti₁₀C₇N₃ reinforced composite welding wire,the increment is 7%,8%and 6%,respectively.?4?The ultimate strength of 7075-T651 aluminum alloy welded with 2wt%and3wt%WC_p/Al-5Mg composites welding wire is 3.4%and 5.6%higher than that of Al-5Mg alloy,respectively.The slow stress corrosion tensile showed that the corrosion time was prolonged by 16.2%and 4.4%,respectively.?5?The friction and wear tests show that the friction coefficient of the composites varies between 0.6 and 0.8,which is basically consistent with that of the matrix materials.However,the linear wear rate is slightly lower than that of the matrix alloy.When 7075-T651aluminum alloy surface surfacing composite material,the friction coefficient of the surfacing layer is about 94.8%higher than that of the base metal,and the line wear rate is reduced by76%.