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Effect of Solution Temperature on Size and Quantity of γ′ and η Phases in LF9 Nickel-based Superalloy and Its Impact Property

Materials for Mechanical Engineering 2009
Chang Wang

Summary

This study examined how solution treatment temperature affects the size and quantity of strengthening precipitate phases in a nickel-based superalloy, finding that the gamma-prime phase grows significantly at higher temperatures while impact toughness changes accordingly. The results guide heat treatment optimization for nickel superalloys used in high-temperature industrial applications.

The changes of γ′ and η phases in LF9 nickel-based alloy after solution treatment at 800-1 040 ℃ for 1 h and then water quenched were studied by SEM,TEM,EDS and ICP-AES methods and the impact toughness of the alloy was measured using impact tester.The results showed that the γ′ phase in the alloy would grow up at high temperatures.For example,the average size of γ′ phase in original forging microstructure was about 20 nm,became 120 nm at 980 ℃ and dissolved completely at 1 020 ℃.The secondary parallel η phase grew up outward along grain boundaries at 820 ℃,reached peak value at 980 ℃ and dissolved completely at 1 040 ℃.At the same time,the γ′-depleted-zone appeared beside the growing η phase.The microplastic effect of the γ′-depleted-zone reduced the crack diffusion rate and thus improved the alloy ductility.However,the increase of the precipitation quantity and size of the η phase decreased the impact tonghness of the alloy.

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