EFFECTS OF RE CONCENTRATION ON THE EXPANSIVITY OF NIRE ALLOYS TO 1200K

Measurements of the thermal expansion dl/l and hence the coefficient o f thermal expansion alpha are reported for Ni100-xRex alloys (x = 0, 5 , 8, 10, 12, 16 and 25%) in the temperature range of 300 to 1300 K usi ng a dilatometer. Room temperature x-ray diffraction studies show that for x greater than or equal to 12%, a small fraction of Re begins to precipitate out, in addition to the dominant face-centred cubic (fcc) phase whose lattice constant increases linearly with x. The variations of alpha with x plotted at selected temperatures of 503, 903 and 1203 K shows that for x less than or equal to 10%, alpha decreases with in creasing x at 503 and 903 K, whereas it remains practically constant w ith x at 1203 K. The latter result is in agreement with the prediction s of Mei et al (1994 Alloy Modeling and Design ed G M Stocks and P E A Turchi (Warrendale, PA: TMS Publishing)) using molecular dynamics sim ulations. The variation of alpha with x shows a minimum at x = 12% at all temperatures. The possible role of shear stresses in the dendritic grain structure of these alloys on measured alpha below 1000 K is dis cussed.