However, current mechanical characterization of iridium alloys has been limited to relatively low strain rates (below 50В s в€’1), which are not sufficiently high for their potential applications. High-strain-rate and high-temperature stressвЂ“strain data are thus needed to develop strain-rate and temperature dependent material models for safety analysis. In some applications, the high-temperature impact response of the material must be fully understood in order to meet the safety requirements for the design of components. Iridium alloys possess unique property combinations of high melting temperature, high-temperature strength and ductility, and excellent oxidation and corrosion resistance, making them ideal for high-temperature applications. The iridium alloy exhibited high ductility in stressвЂ“strain response that strongly depended on strain-rate and temperature.

The effects of strain rate and temperature on the tensile stressвЂ“strain response of the iridium alloy were determined. The dynamic high-temperature tensile stressвЂ“strain curves of a DOP-26 iridium alloy were experimentally obtained at two different strain rates (~10В s в€’1) and temperatures (~7В вЊ). A pair of high-sensitivity semiconductor strain gages was used to measure the weak transmitted force due to the low flow stress in the thin specimen at elevated temperatures. A laser system was applied to directly measure the displacements at both ends of the tensile specimen in order to calculate the strain in the specimen. A preload system was developed to generate a small pretension load in the bar system during heating in order to compensate for the effect of thermal expansion generated in the high-temperature tensile specimen. The specimen was heated to elevated temperatures with an induction coil heater before dynamic loading whereas, a cooling system was applied to keep the bars at room temperature during heating. Conventional Kolsky tension bar techniques were modified to characterize an iridium alloy in tension at elevated strain rates and temperatures.

Iridium bar