Hot Deformation Behavior Of Co-29Cr-6Mo-2Cu Alloy And Its Effect On Corrosion And Antibacterial Properties

The Co based alloys were used in joint implants replace due to excellent wear resistance,corrosion resistance and biocompatibility.Previous study has shown that Co-2Cu alloy exhibited very strong antibacterial property,but the addition of Cu also changed the mechanical property.To optimize the deformation processing,the hot deformation behavior of Co-2Cu alloy was studied,a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn in this paper.The flow behavior curves and the microstructures were studied.To study the influence of Cu to phase transformation,heat treatment for different times to alloys with different Cu contents was performed following the study of microstructures and phase composition.Using electrochemical workstation,ion release and plate counting,the influence of the hot deformation to corrosion resistance and antibacterial property was studied.The hot deformation at a temperature range from 950?-1150?,a strain rate range from 0.008s-1-5s-1 was performed.A constitutive equation was established and a hot processing map was drawn.It was found the flow stress of the Co-2Cu alloy increased with the increasing of the strain rate and decreased with the increasing of the deforming temperature.Microstructure observation indicated that the grain size increased with the increasing of the deformation temperature but decreased with the increasing of the strain rate.The final optimized deformation process was:a deformation temperature from 1050?to 1100?,and a strain rate from 0.008s-1 to 0.2s-1,where a completely recrystallized and homogeneously distributed microstructure would be obtained.Heat treatment at 900? for different times was performed to Co-OCu,Co-2Cu and Co-4Cu.By studying the microstructures and phase composition,it was found that,CoCrMo alloys without Cu addition transformed from ? to ? phase completely while ? phase only occupied about 80%in the alloys with 2wt%and 4wt%Cu addition.It was supposed that the Cu addition inhibited the generation of ? phase which could induce the transformation from ? to ? phase,and inhibited the phase transformation.Hot deformation at 1050? increased the corrosion resistance while hot deformation at 1100? and 1150? decreased the corrosion resistance.The alloy deformed at 1100?,0.04s-1 exhibited the lowest corrosion resistance.The hot deformation decreased the release of Co2+,and increased the release of Cu2+.The hot deformation didn't change the antibacterial property.