AGING EFFECTS ON THE CREEP-BEHAVIOR OF THE NEAR-ALPHA TITANIUM-ALLOY TI-1100

During aging of the silicon-bearing, near-alpha titanium alloy Ti-1100 at the service temperature of 593 degrees C, the precipitation of Ti3Al and silicide particles has been observed, The objective of this article is to determine the influence of these precipitates on creep behavior, Stress relaxation tests, with the advantage of needing only a short time to produce a complete creep curve, were used to determine the creep behavior of Ti-1100, These accelerated creep tests reduce the chance of metallurgical changes that could occur in the long time required to perform conventional creep tests, The creep results obtained from the stress relaxation tests were verified with those obtained from conventional monotonic creep tests, Aging of the material for 500 h at 593 degrees C, where full precipitation of Ti3Al is assumed to be incomplete, resulted in a small decrease in creep resistance compared to the unaged condition, Specimens aged for 1000 h, which corresponds to the averaged condition in which the precipitation of Ti3Al is expected to be completed, were also examined, It was observed that these specimens yielded creep resistance similar to that of the unaged condition. Material aging for 1000 h followed by a special heat treatment, which results in the dissolution of Ti3Al particles, although not affecting the silicide precipitates, resulted in the poorest creep resistance of the aging conditions investigated, The major conclusion of this study is that the presence of Ti3Al has a beneficial influence on the creep resistance of Ti-1100 alloy.