Abstract
Several near-[alpha] and ([alpha] + [beta]) titanium alloys have been developed for high-temperature applications in jet engines. The important feature in these alloys is the addition of a small amount of silicon to enhance creep resistance at elevated temperatures up to about 873 K. The near-[alpha] alloy of nominal composition Ti-6Al-5Zr-0.5Mo-0.25Si (alloy 685) is a commercial titanium alloy developed for use up to 823 K with its [beta] transus at [approximately] 1293 K. It is mechanically processed in the [beta] range, while the commercial heat treatment consists of solution treatment at 1323 K followed by oil quenching and aging/stress relieving for 24 hours at 823 K. Several investigations have been carried out to study the effect of cooling rate from [beta]-solutionizing temperature and aging for 24 hours at different temperatures in the range of 823-1073 K on the microstructure and mechanical properties of the alloy. However, only limited studies have focused on investigating the effect of aging at 823 K, the temperature of the so-called stabilization treatment. It may be noted that while aging of the ternary alloy Ti-5Zr-1Si at 823 K leads to significant hardening due to precipitation of the silicides, only a small degree of hardening has beenmore » reported in the alloy 685 in aging for 24 hours. However, a noticeably increased aging response was observed with increasing cold work in the [beta]-solutionized and water-quenched alloy 685. The present communication aims to provide some evidence for a possible explanation to the aging response in alloy 685.« less
Published Version
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