Strategy for preventing excessive wear rate at high loads in bulk metallic glass composites

The effect of nickel additions to tune the wear performance of Cu45.5Zr51Al3.5 at.% alloy has been studied to present a new strategy for preventing excessive wear rate at high loads in metallic glass composites. This strategy consists of proper selection of a doping element in controlled concentrations with the ability to decrease the glass transition temperature (Tg) of the alloy so that the friction temperature during sliding is close to the Tg. This enables the formation of crystalline phases and their subsequent oxidation (lubricating layer) on the contact surface during sliding thus enhancing the wear resistance. Proper doping can also contribute towards the wear resistance when the content of the doping element promotes the martensitic transformation. The results show that the main wear mechanism for the three studied alloys (Cu45.5Zr51Al3.5, Cu44.5Zr51Al3.5Ni1 and Cu43.5Zr51Al3.5Ni2 at.%) is governed by delamination and the mass loss increases with increasing load from 1 to 10 N. However, for the maximum load of 15 N, the calculated friction temperature is close to Tg for the Ni-containing alloys and partial crystallization and oxidation take place resulting in a mass loss decrease from about 2.6 mg (at 10 N) to about 2.1 mg (at 15 N).