Effect of microalloying in a near alpha titanium alloy

IMI 834 is a recently developed alloy, for aeroengine applications up to 86 3K. These alloys exhibited the best high temperature properties of all the near cr alloys. This paper presents exploratory research work conducted for further enhancement of high temperature capabilities of IMI 834 by microal loying. Pancakes of IMI 834 alloy with microadditions such as tantalum, bismuth, ir on, cobalt, nickel, boron and misch metal (Mm) were prepared by vacuum are melting. These alloys were evaluated for strength and creep at 873 K for va rieties of microstructures. The results indicate that alloys containing eutectoid formers (iron, cobalt , nickel, and bismuth) show the lower strength whereas alloys containing ta ntalum, boron, Mm exhibit higher strength than the base IMI 834. Eutectoid formers, in general, have adverse effect on the creep properties as well. A lloying additions that are isomorphous in titanium such as tantalum have no t resulted in the improvement of the creep properties. An assessment of cre ep properties of the alloys containing boron and Mm indicates that creep pr operties of these alloys are relatively insensititive to cooling rates. Thi s allows optimisation of other properties such as yield strength by choice of an appropriate heat treatment without deterioration of creep properties.