Platinum alloys based on Pt–Pt3Al for ultra-high temperature use

Platinum–aluminium alloys based on the L12 compound Pt3Al have potential as high-strength alloys with superior environmental resistance at ultra-high temperatures. Two-phase microstructures, analogous to the nickel-base superalloys, and consisting of the intermetallic compound Pt3Al and the (Pt) solid solution, can be engineered to have the attributes of microstructural stability, environmental resistance, high-temperature strength and room-temperature ductility. Pt3Al exists as a tetragonal phase below 1290 °C, and ternary alloying is employed both to stabilise the L12 crystal form of Pt3Al and as a solid-solution strengthener of the (Pt) phase. In this investigation, the phase relations of the Pt-rich comers of eight Pt–Al–X ternary systems (X=Ru, Re, W, Mo, Ni, Ti, Ta and Cr) are characterised. The solubility of element X in (Pt) and Pt3Al, and the effect on the phase boundaries, was assessed using SEM-EDS. XRD was used to assess which crystal variant of Pt3Al was stabilised. Preliminary room-temperature mechanical testing was carried out on the alloys. This assessment has been used to select the most promising systems for further characterisation.