Optimization of composition and heat treatment of age-hardened Pt-Al-Cr-Ni alloys

The objective of this work was to produce an alloy showing a microstructure similar to Ni-base superalloys, but with Pt as base metal. The Pt-base alloys with various contents of Al, Cr, and Ni were arc melted. Solution heat treatments at 1450 degreesC followed by water quenching lead to single-phase alloys. Ageing at 1000 degreesC resulted in the precipitation of L 12 ordered particles. An alloy with 11 at. pct Al, 3 at. pct Cr, 6 at. pct Ni, and Pt balance shows cuboidal precipitates with edge lengths of 200 to 500 nm along with a volume fraction of 23 pct and a lattice misfit of -0.1 pct. Aging at 1100 degreesC leads to coarsening of precipitates. Volume fraction and morphology of the precipitates were investigated by scanning electron microscopy and optical microscopy. X-ray diffraction as well as transmission electron microscopy (TEM) were applied to verify the crystal structure.