Surface hardness improvement of Al via inserting ceramic powders by ultrasonic mechanical coating and armoring with subsequent annealing

In this study, ultrasonic mechanical coating and armoring (UMCA) with subsequent annealing is applied to improve surface hardness of Al. The micro-scaled CuO powders are bombarded and inserted into Al by UMCA, leading to the increment in surface hardness by 6 times. The grain refinement, work hardening and dispersion hardening are contributed to surface hardening. Moreover, the reaction temperature between CuO and Al can be reduced by severe UMCA process. Thus, after UMCA and subsequent annealing at 500 °C, the surface hardness can be increased by 10 times, which can mainly refer to the dispersion strengthening caused by transformed nano-size Cu2O.