时效时间对固溶态及冷变形态钴基合金显微组织和力学性能影响

Effect of aging time on microstructure and mechanical properties of solid solution and cold deformation cobalt-based alloys

对固溶态及冷变形态的两种钴基合金L605、L605Mo进行600℃不同时间的时效处理,采用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)及力学性能测试等方法研究时效时间对合金显微组织与力学性能的影响,并分析了冷变形及Mo元素对时效行为的影响。结果表明:经过冷变形的合金经600℃时效后,强度、硬度提高,塑性韧性下降;而固溶态合金经时效后,力学性能变化不明显,其中,抗拉强度最高的合金为时效12 h的s25-13合金。时效初期碳化物析出及层错形成使合金强度提高,但随着时效时间的延长,冷变形形成的具有强化作用的变形带在时效过程中退化会使合金强度减小。M_(6)C含量随时效时间延长而不断增加,冷变形促进M_(23)C_(6)及M_(6)C析出使合金的时效强化效果更加显著。Mo能降低层错能,促进时效过程中M_(23)C_(6)、M_(6)C和层错的形成以及层错的交割,从而提高合金的强度。因此,添加Mo的合金经时效处理后强度、硬度均高于未添加Mo的合金。

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 M_(6)C increases with the increase of aging time.Cold deformation promotes the precipitation of M_(23)C_(6)and M_(6)C,which makes the aging strengthening effect more significant.Because Mo can reduce the stacking fault energy,promote the formation of M_(23)C_(6),M_(6)C,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.