Microstructure of ordered Pd–8at.%Y alloys

The microstructure of palladium–yttrium alloys has been investigated in this paper, the two alloys were the Pd–7.52at.%Y alloy and Pd–8.22at.%Y alloy, respectively. The Pd–Y alloy ingots were prepared by melting the yttrium powder and palladium powder in a vacuum induction furnace. The resultant alloys were homogenized at 950°C for 6 h. Then cold rolled to produce foil. Some of them were quenched into water from 900, 920 and 940°C, respectively. Finally given a vacuum anneal at 750° C for 40 min and furnace cooled to produce the material in long-range-ordered (LRO) condition. There was an inflection on the curve of electrical resistance vs. temperature, which indicates that the anomaly electrical resistance variation is due to an order–disorder transition. The results of XRD show that Pd3Y typed LRO super-lattice existed in as-annealed samples. After annealing, the average grain size of Pd–8at.%Y alloys become smaller, the grains distribute unequally, and the grain scale for as-quenched and as-annealed samples was 750/mm2 and 760/mm2, respectively. Microstructure was studied by optical and transmission electron microscopy. Anti-phase domain boundary (APB) was found in the as-annealed alloys. The cell-like structures in the TEM photo were not complete.