Effect of microstructure characteristics on the fatigue crack propagation rate of GH864 alloy
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摘要: 利用光學顯微鏡、場發射掃描電鏡等手段,研究了GH864合金三種軋制態組織經熱處理后的演變過程,分析了熱處理后不同組織對室溫沖擊韌性及高溫650℃裂紋擴展速率的影響.結果表明,GH864合金由初始軋制態組織經標準熱處理后(1020℃,4h/空冷→845℃,4h/空冷→760℃,16h/空冷)獲得的晶粒組織,其晶粒組織演變具有明顯的一致性,而合金的晶界碳化物分布及基體γ'強化相沒有明顯差別,其分布狀態及尺寸大小基本一致.熱處理后的晶粒尺寸越大,抗裂紋擴展能力越好,合金的室溫沖擊韌性越低;熱處理后形成的項鏈狀組織,對合金沖擊韌性及裂紋擴展速率有較好的影響.Abstract: The evolution of three different initial microstructures of GH864 alloy after heat treatment was studied by optical microscopy(OM) and field emission scanning electron microscopy(FESEM).The impact toughness at room temperature and crack propagation rate at 650℃ were analyzed after heat treatment.The results indicate that the grain microstructural evolution of GH864 alloy is hereditary between initial forging state and heat treatment state after 1020℃,4h/air cooling→845℃,4h/air cooling→760℃,16h/air cooling,while carbides in grain boundaries and γ' phases are not significantly different.The larger the grain size,the better crack propagation behavior the alloy has,and the worse the impact toughness is.It is highlighting that the necklace microstructure has a better effect to improve the impact toughness and crack propagation behavior of GH864 alloy.
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Key words:
- superalloys /
- nickel base alloys /
- microstructural evolution /
- precipitates /
- crack propagation
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