||Because of the excellent physical, chemical properties and light weight, aluminum is widely used in industry and engineering. However, aluminum surface display poor hardness so that the surface modification has been developed and wide studies to improve this situation. The most surface modifications have obstacles or limitation such as inconvenient preparation, respectively high operating temperature, and long operating time etc. In this study, the ultrasonic mechanical coating and armouring (UMCA) will be applied to improve the surface mechanical properties. The UMCA provides a simple and convenient method to obtain better properties of aluminum surface. It coats ceramic powders CuO on a substrate through high-energy ball impacts which form the aluminum metal matrix composite. The ceramic powders are harming into Al substrates leading to increasing the hardness. Although UMCA process can modify the surface properties, the combination is a big deal for UMCA process. Thus, the heat treatment will be proceeded to enhance the boding between coating layers and a substrate. During the heating, Al substrate reacted with powders to generate the intermetallic compounds which further increased the hardness of Al. |
After UMCA process, the surface hardness of the UMCA samples can increase 4 times higher than the untreated samples, from 47 Hv up to 279 Hv. On the contrary, On the contrary, the surface hardness decreased to the level of base 1050 Al after exorbitant (580oC) heat treatment due to the generation of pure copper, coarsening of Al2Cu and the elimination of UMCA induced work hardening. Therefore, the heating temperature was lowered and tried at different temperatures. The best resulting hardness is about 10 times of that of the bare Al when sample with 20 min UMCA and 500oC-60 min heat treatment, from 47 Hv up to 426 Hv.