Numerical Modeling and Optimization for the Laser-Resistance Hybrid Thermal Imprinting of Pd-based Metallic Glass for Better Formability

Abstract

Metallic glass is an advanced non-crystalline material which has great application potential in the biomedical field, whose manufacturing quality was related to the temperature history significantly. In the present research, the laser-resistance hybrid heating process of Pd_42.5Ni_7.5Cu₃₀P₂₀ bulk metallic glass (BMG) was analyzed numerically to improve its formability during thermal imprinting. The glass transition temperature and onset temperature of crystallization of BMG under different heating rates were measured to clarify the time-temperature-transformation diagram. The contact heat transfer coefficient in heating equipment was calibrated by experiment. The in-house finite element (FE) code JWRIAN-HYBRID was employed to predict the temperature distribution and thermal cycles on BMG. The optimization of heating process was discussed in detail. The result showed that the laser heating efficiency was about 4.4%. In the designed heating process, the maximum temperature of BMG reached about 400 ℃ and it can only stay in the expected temperature range for 35 s. With the optimized double pulse resistance heating, the duration time of BMG in supercooled liquid region extended to 720 s, which was enough to realize a 30-μm grid in thermal imprinting. In the hybrid heating method, resistance heating gave more contribution to preheating and insulation for the smooth heat input; laser heating was employed to supply energy and control temperature.