Preparation and Size Effect of GH3600 Nickel-Based Superalloy Ultra-Thin Strips
Nickel-based superalloys have gathered much attention recently due to their excellent per-formance at high temperatures and corrosion resistance.Furthermore,their advancement is a crucial indi-cator to determine the development level of metallic materials.Thus,rapid development in microsystem technology which focuses on development of lightweight and miniaturized materials is required.More-over,the demand for micromaterials such as ultra-thin strips is also growing,leading to higher demand and better performance requirements.China's production of ultra-thin strips started relatively late and nickel-based ultra-thin strips rely on imports.Strengthening the production research of nickel-based ultra-thin strips,meeting the needs of aerospace and emerging microsystems,and removing import depen-dence are key issues that need to be addressed in future.The accurate acquisition of microstructure vari-ations and strip properties after thinning and heat treatment is crucial in controlling the forming accuracy and preventing defects.Remarkably,the GH3600 nickel-based superalloy with thicknesses from 0.5 mm with polycrystalline layer to 0.07 mm with local single crystal layer was obtained by cold rolling and an-nealing.The effects of cold rolling reduction and annealing temperature on the microstructure and me-chanical properties of the superalloy were investigated,and changes in the microstructure and mechani-cal properties caused by thickness variation were analyzed.The results reveal that with the increase of cold rolling reduction,the austenite grains in the alloy are elongated along the rolling direction,and the annealing twins gradually disappear.A complete recrystallization microstructure was obtained after fur-ther annealing,and grain size increased with the annealing temperature while the strength and hardness decreased.After annealing at the same temperature,the material's yield strength increases with the re-duction and refinement of the recrystallized grain.However,as the strip thickness decreases,the grain layer decreases along the direction of the strip thickness.After annealing at 1000 and 1050℃,abnormal coarse grains appear in 0.07 mm thick strips,leading to the appearance of single grains in some areas along the thickness direction of the ultra-thin strips.The tensile strength and elongation of the strip are"smaller and weaker"with the decrease of strip thickness/average grain size ratio due to the size effect.The comparative analysis demonstrated that the average grain size of GH3600 ultra-thin strips annealed at 800-900℃ is approximately 7 μm,the local orientation difference is approximately 0.5,the yield and ten-sile strengths could reach up to 400 and 600 MPa,and the elongation is approximately 13%,respectively.
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