Investigation of the hardness improvement for Al-A380 alloy using the controlled atmosphere in the mechanical stirring casting method

Abstract

This work studied the semisolid (SSM) Al-A380 alloy formed by mechanical stirring under the circumstances of controlled atmosphere with argon gas. The A380 aluminium alloy produced due to this process can be used instead of the forging processes or die casting with better mechanical properties. In this paper, first, the effects of the solid fraction, the stirring speed and the mold temperature on the hardness and microstructure are studied using a mechanical stirrer. Then some tests such as XRD and ultrasonic test are done to investigate the effect of using the controlled atmosphere system. By optimizing the forming parameters and with the breaking of primary a phase dendrites, the microstructure will be changed to the spherical form, therefore the mechanical properties will be improved. The results showed that the hardness of the billets has increased significantly due to the uniform grains distribution at the condition of 580 ℃ stirring temperature, 300 r/min stirring speed and mold temperature of 100 ℃. Also, the process properly optimized with the controlled atmosphere. In this condition, the results illustrated that the mechanical properties of the alloy increased around 30%.