Size effect on friction and wear mechanisms of bulk metallic glass

- Friction and wear of BMG change with sample size.
- Fracture strength and plasticity play an important role in wear mechanism of BMG.
- Pre-existence of shear bands in the wear track accelerate the wear rate.
- Variation of wear rate is not an effect of cooling rate/geometric instability of sample.

This paper investigates the effect of sample size on the friction and wear of a bulk metallic glass (BMG), Ti40Zr25Ni3Cu12Be20. The sliding tests were conducted on a pin-on-disk tribometer and the microstructural analyses were carried out by SEM and TEM. It was found that friction and wear of BMG change with sample size. The fracture strength and plasticity of BMG play a central role in the mechanism variation of friction and wear. When the pin diameter is 5 mm, the wear track showed typical abrasive morphology (without noticeable ductile features) containing shear bands which resulted in maximum wear under this condition. With the decrease of sample size, ductility and fracture strength of BMG increased, resulting in higher wear resistance and friction for smaller samples. The paper also concluded that the observed variations in mechanical and tribological properties of BMG with sample size are not due to the cooling rate effect or geometric instability or tilting of the specimen.