Effects Of Cold Drawing And Heat Treatments On Microstructure And Properties Of Cu-12%Fe Alloy

Cu-12%Fe filamentary composites were prepared by casting,prior heat treating and cold drawing.The microstructure evolution of the alloys during cold drawing and the relationship between microstructure and properties were investigated.The effects of prior heat treatments,intermediate heat treatments,final heat treatments and rare-earth elements on the microstructure and properties of Cu-12%Fe composites during drawing deformation were discussed.Coarse primary Fe dendrites and secondary Fe particles exist in the Cu matrix in the as-cast Cu-12%Fe alloy.Quenching and aging treatment or homogenizing treatment prior to drawing deformation refine the primary dendrites,remove the solute segregation along Cu grain boundaries and promote the precipitation of secondary Fe particles.During cold drawing,a filamentary structure dispersed in Cu matrix is formed from the primary Fe phase.The filaments align parallel to the wire axis on the longitudinal section and the Fe phase has a curled and folded morphology on the transverse section.There are different preferred orientations formed in drawing strain in the axial and radial directions in Cu and Fe filaments.The microstructure scales of Fe filaments exponentially decrease with the increase in draw ratio.The density of the interface between Cu and Fe phases exponentially increases with the increase in aspect ratio of Fe filaments.With the increase in draw ratio,the strain of Fe grains linearly increases at the draw ratios lower than 6.0 and deviates from the linear relation at those higher than 6.0.For Cu-12%Fe alloy,the strength and hardness increase and electrical conductivity decreases with the increase in draw ratio.There is a Hall-Petch relationship between the strength or hardness and Fe filament spacing.The decrease of conductivity is mainly attributed to the increase of interface scattering.Prior heat treatments and intermediate heat treatments facilitate the deformation of Fe dendrites and promote the precipitation of Fe,which remarkably improves the strength levels and electrical properties during the deformation process.However,the decrease of conductivity of Cu-12%Fe with intermediate heat treatments has a high ratio,and result in a lower conductivity at high draw ratio than the alloy without heat treatments.The strength,hardness and elastic modulus decrease but the electrical conductivity and plastic deformation capacity increase with the increase in annealing temperature for the Cu-12%Fe microcomposites.Adding 0.1%rare earth elements into Cu-12%Fe can refine the as-cast microstructure,and improve the Young's modulus but decrease strength and conductivity.For Cu-12%Fe-0.1%RE,intermediate heat treatments obviously improve the electrical conductivity during the deformation process.