Characteristic behavior of Pt-based metallic glass under rapid heating and its application to microforming

In this paper, we studied characteristic behavior of Pt_48.75Pd_9.75Cu_19.5P₂₂ metallic glass during rapid heating. We first rapidly heated a cylindrical specimen of 2mm in diameter and 5mm in height by induction heating at a rate of up to 100K/s. During the heating, glass transition temperature T_g and the crystallization temperature T_x increase with increasing heating rate. The material exhibits a Newtonian viscous flow in the supercooled liquid temperature range, and the normal viscosity decreases with increasing heating rate. The normal viscosity is 2×10³Pas at a heating rate of 100K/s. We developed a new microforming system as an application of this phenomenon. The system consists of a rapid resistance-heating unit for foil specimens, a glass transition detector, a linear actuator for driving a tool, and the associated control circuits. With this apparatus, we transferred a three-dimensional micro-shape to the materials within 30s. A conventional superplastic forging system requires a long time to heat work specimens and to deform them. The developed system thus facilitates mass production of micro parts for micro electro mechanical systems (MEMS).