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 turn in height by induction heating at a rate of up to 100 K/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 x 10(3) 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 electromechanical systems (MEMS). (C) 2003 Elsevier B.V. All rights reserved.