Thermodynamics and kinetics of laser induced transformation in zirconium based bulk metallic glass

• Change in Tg, crystallization temperature, and enthalpies of Zr-based BMG occurred during isothermal laser treatment
• Volume fractions of amorphous and crystalline phases vary as function of laser processing parameters
• Maximum devitrification occurred in laser treated sub-surface regions
• Slight compositional change resulted in increase in crystallization temperature for partially laser devitrified BMG samples
• Tg decreased due to structural relaxation of amorphous phase during laser processing at the slowest scanning speed

Laser-material interaction for a Zirconium based bulk metallic glass was investigated. The change in glass transition, crystallization temperature and enthalpies along with microstructure of the amorphous alloy was explained by the non-isothermal history experienced during processing. Varying volume fractions of amorphous and crystalline phases were found through the cross-section. A finite element based multi-physics modeling approach was employed to predict the temperature history and associated cooling rates during laser processing. Maximum devitrification occurred in sub-surface regions that experienced suitable combination of thermodynamic and kinetic conditions during laser treatment. It was demonstrated that the location and length scale of crystallized zone can be controlled by tailoring the laser processing parameters.