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

In this paper, we studied characteristic behavior of Pt48.75Pd9.75Cu19.5P22 metallic glass during rapid heating. We first rapidly heated a cylindrical specimen of 2 mm in diameter and 5 mm in height by induction heating at a rate of up to 100 K/s. During the heating, glass transition temperature Tg and the crystallization temperature Tx 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 2×103 Pa s at a heating rate of 100 K/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 30 s. 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).