Synthesis and characteristics of consolidated nanocrystalline two-phase Ag50Ni50 alloy by hot pressing

Silver and nickel are mutually only very slightly soluble and have a positi ve heat of mixing. Ag50Ni50 powder was prepared by mechanical alloying (MA) for 200 h and subsequent hot pressing (HP) at 620 degrees C under 60 MP3, XRD results indicated that ball milling produced a two-phase mixture of sup ersaturated, nanocrystalline Ag-rich (alpha-phase) and Ni-rich (beta-phase) solid solutions with grain sizes of 5 and 3 nm, respectively. The grain si zes increased to about 40 and 3-6 nm after hot pressing. The HP Ag50Ni50 ha d a density very close to the theoretical value. The HP alloy consisted of an interconnected network of the alpha-phase and islands of a two-nanophase mixture rich in the beta-phase. The tability of the microstructure of the alloy and the effects of mechanical alloying on the supersaturation of the two phases and on the formation of the Ag-rich network are also discussed. (C) 2000 Elsevier Science S.A. All rights reserved.