Laser solid forming Zr-based bulk metallic glass

Abstract

The crystallization characteristics of Zr 55Al 10Ni 5Cu 30 bulk metallic glasses BMGs during pulsed laser surface melting (PLSM) were examined, and the crystallization behavior during Laser solid forming (LSF) of Zr 55Al 10Ni 5Cu 30 BMGs with the pre-laid powder method on the amorphous substrates was further investigated. It was found that the BMG could keep the amorphous state after PLSM with six pulses and crystallization began to occur in heat-affected zone (HAZ) after PLSM with twelve pulses. There was no crystallization occurred in the deposit with one and two layers during LSF, and the volume fraction of amorphous phase in the deposit with seven layers deposit was about 92.44%. The crystallization degree did not increase remarkably with the increasing of deposited layers. The crystallization mainly occurred in HAZ during PLSM and LSF. A physical model was proposed to describe laser solid forming of BMGs, which explained the formation mechanism of BMGs during laser solid forming. It is shown that the crystallization during the PLSM and LSF process was mainly caused by the accumulation of structural relaxation in the HAZ. The size of HAZ should be smaller than the thickness of single pulsed laser deposited layer during LSF of BMGs without crystallization. Based on the present model and experiment results, we can reckon that bulk metallic glasses could be achieved by LSF without size limitation.