Boron Segregation to Grain Boundaries and Improved Ductility in Pt + 30 Wt Pct Rh + 8WtPctW

Boron additions of up to 75 wt ppm have been observed to improve the room temperature strength and ductility of a Pt + 30 wt pct Rh + 8 wt pct W alloy. Alloys without boron fail intergranularly, and those with 75 wt ppm boron added fail in a mixed intergranular-transgranular mode. Auger electron spectroscopy on intergranular fracture surfaces indicated that boron segregates strongly to grain boundaries in the boron doped alloys. Transmission electron microscopy of alloys with and without boron indicated that both were free of internal precipitates. The observed improvements in strength and ductility appear to be related to boron enrichment within a few atomic distances of the grain boundary.