Effect of Strain Rate on Ductile-to-Brittle Transition Temperature of a Free-Standing Pt-Aluminide Bond Coat

Abstract

The ductile-to-brittle transition temperature (DBTT) of a free-standing Pt-aluminide (PtAl) bondcoat was determined using the microtensile testing method and the effect of strain rate variation, in the range 10 À5 to 10 À1 s À1 , on the DBTT studied. The DBTT increased appreciably with the increase in strain rate. The activation energy determined for brittle-to-ductile transition, suggested that such transition is most likely associated with vacancy diffusion. Climb of h100i dislocations observed in analysis of dislocation structure using a transmission electron microscope (TEM) supported the preceding mechanism.

Small-Scale Mechanical Testing

“…High-activity, aluminum-rich diffusion aluminides have been studied with respect to the effects of strain rate and platinum content on the ductile-brittle transition (237) (Figure 23), flow stress, the importance of grip design in minimizing stress concentrations, and changes in dislocation substructure evolution with temperature (237)(238)(239)(240)(241)(242). The brittle-ductile transitions of β-γ-γ were measured in a non-line of sight deposition process for MCrAlY (243).…”