Thermophysical Properties of Solid and Liquid 90Ti–6Al–4V in the Temperature Range from 1400 to 2300 K Measured by Millisecond and Microsecond Pulse-Heating Techniques

Abstract

The heat capacity and electrical resistivity of 90Ti–6Al–4V were measured in the temperature range from 1400 to 2300 K by two pulse-heating systems, operating in the millisecond and microsecond time regimes. The millisecond-resolution technique is based on resistive self-heating of a tube-shaped specimen from room temperature to melting in less than 500 ms. In this technique, the current through the specimen, the voltage drop along a defined portion of the specimen, and the temperature of the specimen are measured every 0.5 ms. The microsecond-resolution technique is based on the same principle as the millisecond-resolution technique except for using a rod-shaped specimen, a faster heating rate (by a factor of 10,000), and faster data recording (every 0.5 μs). Due to the rapid heating with the microsecond system, the specimen keeps its shape even in the liquid phase while measurements are made up to approximately 300 K above the melting temperature. A comparison between the results obtained from the two systems with very different heating rates shows significant differences in phase transition and melting behavior. The very high heating rate of the microsecond system shifts the solid–solid phase transition from the (α+β) to the β phase to a higher temperature, and changes the behavior of melting from melting over a temperature range to melting at a constant temperature like an eutectic alloy or a pure metal.