单一时效处理对MAR-M246高温合金拉伸和持久性能的影响OA

Taking investment-cast MAR-M246 superalloy as the research material,a single aging treatment is adopted to replace the conventional solution plus double aging heat treatment,and the effects of single aging treatment on the microstructure,room-temperature/high-temperature tensile properties,and medium/high-temperature stress rupture properties of MAR-M246 superalloy are investigated.A high-resolution field-emission scanning electron microscope(FE-SEM)is used to characterize the microstructures and fracture morphologies of the as-cast and aged alloys,while tensile and stress rupture tests were carried out on alloys under different states.The results show that the microstructures of both as-cast and aged MAR-M246 superalloys consist of γ matrix,γ′precipitates,blocky intragranular MC carbides,strip-like intergranular MC carbides,and γ+γ′ eutectic phases.After aging treatment,the volume fraction of γ′ precipitates increases from 42.68%in the as-cast alloy to 49.85%in the aged alloy,and the average size of γ′ precipitates rises from(301±9)nm to(321±12)nm with a more uniform size distribution;meanwhile,the cubicity of γ′ precipitates is markedly enhanced after aging.After aging,the room-temperature yield strength of MAR-M246 superalloy is slightly improved,and the elongation after fracture at 900℃increases significantly.Under the condition of 760℃and 724 MPa,the stress rupture life of MAR-M246 superalloy is remarkably extended from 18.15 h(as-cast)to 38.23 h(aged),and the stress rupture elongation rises from 3.14%(as-cast)to 5.4%(aged).However,at 980℃and 225 MPa,the stress rupture life declines from 79.58 h(as-cast)to 45.48 h(aged).These phenomena are mainly attributed to the fact that the γ′ precipitates with higher cubicity generated during aging are prone to rapid coarsening and rafting.