Separating the effects of Ti3Al and silicide precipitates on the tensile and crack growth behavior at room temperature and 593 °C in a near-alpha titanium alloy

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Aging of silicon-bearing, near-alpha titanium alloys produces two types of precipitate, Ti3Al and (TiZr6Si3 (silicide). A postaging heat treatment that relies on the phenomenon of the critical ordering temperature is used to remove the Ti3Al precipitate while leaving the silicide intact. Three materials—unaged (precipitate free), overaged (Ti3Al plus silicide), and post aging heat treated (silicide only)— are compared. The objective is to identify the separate effects of the Ti3Al and silicide precipitates on tensile and fatigue crack growth behavior at room temperature and 593 °C. The Ti3Al precipitate is largely responsible for the increase in yield stress and for the decrease in ductility at both test temperatures. In contrast, the increase in room temperature fatigue crack growth rate associated with aging is attributed to the silicide, with Ti3Al playing only a minor role. Aging produces a slight improvement in fatigue crack resistance at 593 °C, which also appears to be due to the presence of the silicide precipitate. © 1995, ASM International. All rights reserved.

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Journal of Materials Engineering and Performance