Phase Transformation Characteristic Of Cu-Ti Alloy During Early Aging And Effect On Properties

Copper-Titanium alloy have high strength, high elasticity and good electrical conductivity so that these alloys find wide applications in electrical and electronics industry. And Copper-Titanium alloy is a kind of aging strengthening alloy. At the beginning of aging, it will appear spinodal decomposition and ordering phenomenon.It has been found that the composition design, processing technology and aging treatment will change the phase transformation and property of Copper-Titanium alloy. In this paper, Cu-1.5% Ti and Ti alloy Cu-4.5% alloys have been fabricated and heat-treated under different working process and aging. The characteristics of phase transformation at the early aging stage and properties for the studied alloys were studied by using hardness, electrical conductivity and TEM. The results can be listed as follows:(1) The sequence of the decomposition in the studied Cu-1.5wt%Ti alloy can be summarized as follows: a modulated structure resulting from spinodal decomposition?formation of Ti-enriched zone and ordered fcc phase ?formation of metastable LRO ?'-Cu4 Ti precipitation. The ordered fcc phase shows a cube-on-cube orientation relationship(OR) with matrix, while the long-range ordered(LRO) ?'-Cu4 Ti shows an OR of [001]Cu//[001]?'and(310)Cu//(100)?'.(2) Compared to Cu-1.5wt%Ti, the more concentrated Cu-4.5wt% alloy has faster decomposition during the early aging. The decomposition sequence of Cu-4.5wt%Ti alloy during the aging can be summarized as follows: spinodal decomposition+ {1 1/2 0} long-range ordering +fcc ordering ?? '-Cu4 Tiwith long-range order? cellar Cu3 Ti.(3) The specimens were investigated using the hardness, electrical conductivity measuremrnts, and high resolution electron microscopy. Modulated structure, ordered fcc phase and ?'-Cu4 Ti precipitation can enhance the strengthen of the studied alloys.Compared to the conductivity and hardness of solution treated alloy, the maximum conductivity of cold-rolled and aged Cu-1.5%Ti alloy is about 28%IACS and the maximum hardness of cold-rolled and aged Cu-4.5%Ti alloy is about 410 HV. Itindicates that the pre-deformation before aging treatment can effectively increase the alloy properties.