Spinodal Decomposition in Cu-32.Ni-0.75Si Alloy during Aging

An investigation on transformation of the early stage of aging in Cu-3.2Ni-0.75Si alloy has been conducted by means of transmission electron microscopy and X-ray diffraction. It concludes that a supersaturated Cu-Ni-Si solid solution decomposes firstly by short range ordering, then by spinodal decomposition forming solute rich and solute depleted zones, and lastly Ni-2Si appeared. This paper intrutively explains the coexistence of spinodal decomposition and ordering and phenomenologieally proves the probability of the concomitant reaction.