Effect of two-step aging on microstructure and properties of high-strength aluminum alloys for automobile

The application of high-strength aluminum alloy on the vehicle body will be the development trend of automobile lightweight in the future. The effects of two-step aging on the microstructure and properties of high-strength aluminum alloys for automobile were investigated by tensile tests, electrical conductivity, and transmission electron microscopy (high resolution). The effect of aging temperature on the overall performance is greater than the aging time. The effect of the second-stage aging temperature in the two-step aging parameters is the greatest. As the aging temperature and aging time of the second-stage increase, the size of the aging strengthening phase increases. The mechanical properties decrease and the conductivity increases. The optimized T76 aging system is 120 degrees C/6h+160 degrees C/12h. The precipitation phase is completely coherent with the matrix. The size of length is about 5-8nm, and the size of thickness is about 3-5nm. The optimized T73 aging system is 120 degrees C/6h+170 degrees C/12h, the precipitation phase is semi-coherent with the matrix. The size of length is about 8-15nm, and the size of thickness is about 4-8nm.