Effect of aging time on microstructure and mechanical properties of solid solution and cold deformation cobalt-based alloys
The solid solution and cold forging cobalt base alloys L605 and L605Mo were aged at 600℃for different time.The effects of aging time on the microstructure and mechanical properties of the alloy were studied by means of scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray diffraction(XRD)and mechanical properties test,and the effects of cold deformation and Mo element on aging behavior were analyzed.The results show that the strength and hardness of the cold deformed alloy increase and the plasticity and toughness decrease after aging at 600℃.The mechanical properties of the solid-solution alloy do not change significantly after aging.The alloy with the highest tensile strength is s25-13 alloy aged 12 h.In the early stage of aging,the precipitation of carbides and the formation of stacking faults lead to the improvement of the strength of the alloy.However,with the aging time increasing,the deformation band with strengthening effect produced by cold deformation will degrade during the aging process,which will reduce the strength.The content of M6C increases with the increase of aging time.Cold deformation promotes the precipitation of M23C6 and M6C,which makes the aging strengthening effect more significant.Because Mo can reduce the stacking fault energy,promote the formation of M23C6,M6C,stacking fault and stacking fault intersection during aging,which will improve the strength of the alloy.Therefore,the strength and hardness of the alloy adding Mo after aging treatment are higher than those without Mo.
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