TAILIEUCHUNG - Handbook Heat Treating (1991) WW Part 13

Tham khảo tài liệu 'handbook heat treating (1991) ww part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 980 C 1800 F for 4 h with air cooling 650 C 1200 F for 24 h with air cooling 760 C 1400 F for 8 h with air cooling The 1105 C 2020 F anneal is a partial solution treatment below the y solvus that retains some of the y to limit grain growth. The subsequent treatments precipitate carbides and y . The two-step exposures of first 870 C 1600 F and then 980 C 1800 F are designed to maximize first the nucleation of precipitates and then the rate of growth of the precipitates. The average grain size of the structure produced is about 11 gm with a y volume fraction of about 35 . The fine-grained structure has better mechanical properties at turbine disk application temperatures than that from coarsegrained heat treatment which is designed for higher-temperature applications. The effect of the amount of cold working on the recrystallization and grain growth during subsequent solution treating of the nickel-base superalloy Nimonic 90 is shown in Fig. 11. The effect is similar to the behavior shown for A-286 in Fig. 1. The critical amount of deformation that leads to abnormally large grains is in the range of 2 to 10 reduction in thickness and the grain growth accelerates rapidly at temperatures above 1100 C 2010 F . Fig. 11 Effect of cold work and annealing on grain size for Nimonic 90 sheet cold rolled in steps from to mm to in. thick and annealed at five temperatures The precipitation-hardened superalloys that undergo extensive deformation processing as in sheet forming usually require in-process annealing to maintain temperatures relieve forming stresses and enhance microstructural changes. The annealing practice can also have a marked effect on response to solution treating and aging. This is illustrated by the following two examples for René 41. Like solution-treatment temperatures Fig. 9 high annealing temperatures can dissolve M6C carbides which are useful in preventing formation of M23C6 grain boundary films during aging. Example 4 Effect of .

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