微觀組織和力學(xué)性能的影響
(1. 中國科學(xué)院 金屬研究所，沈陽 110016；
2. 東方汽輪機(jī)有限公司，德陽 618000)
摘 要: 研究不同抽拉速率(4，5，7，9，10 mm/min)對定向凝固DZ445高溫合金微觀組織和力學(xué)性能的影響。結(jié)果表明：隨著抽拉速率由4 mm/min增加到10 mm/min，一次枝晶臂間距λ1和二次枝晶臂間距λ2逐漸減小，枝晶組織逐漸細(xì)化；枝晶干和枝晶間γ′相尺寸也逐漸減小，枝晶間γ′相的尺寸比枝晶干γ′相的大，這種差別隨著凝固速率的增加而減小；合金元素的偏析隨凝固速率的增大越來越嚴(yán)重；除抽拉速率為4 mm/min外，抽拉速率對DZ445合金室溫拉伸性能影響不大；當(dāng)抽拉速率太高或者太低時，合金650 ℃拉伸伸長率均明顯降低；抽拉速率對合金的持久性能影響明顯；當(dāng)抽拉速率為7 mm/min時，合金的拉伸性能、持久性能和微觀組織達(dá)到綜合平衡，為最佳抽拉速率；DZ445定向柱晶合金比同成分K445等軸晶合金具有更好的室溫和高溫拉伸性能及持久性能。
關(guān)鍵字: 定向凝固高溫合金；DZ445合金；抽拉速率；微觀組織；力學(xué)性能
（1. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;
2. Dongfang Turbine Co. Ltd., Deyang 618000, China）
Abstract:The effects of withdrawal rate (4, 5, 7, 9, 10 mm/min) on the microstructure and mechanical properties of directionally solidified superalloy DZ445 were investigated. The results show that with the increase of withdrawal rate from 4 mm/min to 10 mm/min, both the primary and secondary dendrite arm spacing decrease gradually, and the average size of γ′ precipitates well-distributed in both dendrite core and interdendritic, decreases gradually. The average size of γ′ precipitates in dendrite core is smaller than that in interdendritic areas. The tendency of segregation of elements is more intense with the increase of withdrawal rate. At room temperature, the tensile properties of the DZ445 alloy under different withdrawal rates differ slightly, except at 4 mm/min. At 650 ℃, the tensile elongations at both too high and too low withdrawal rate decrease obviously. Besides, the withdrawal rate has an apparent effect on the stress-rupture properties of the DZ445 alloy. To sum up, the alloy under withdrawal rate of 7 mm/min has a good balance of tensile property, stress-rupture property and microstructure. Therefore, 7 mm/min is finally determined to be the optimal withdrawal rate. DZ445 columnar crystal alloy under the optimal withdrawal rate has better tensile property and stress-rupture property than K445 polycrystal alloy, which has the same composition as DZ445 alloy.
Key words: directionally solidified superalloy; DZ445 alloy; withdrawal rate; microstructure; mechanical properties
