用金相、扫描和透射电镜研究了690合金经1450--1550℃, 5 min熔体过热处理对合金再结晶组织和显微硬度的影响。结果表明, 690合金中凝固析出的TiN的体积分数和平均尺寸随着熔体过热温度的升高而降低, 其形态由规则的块状转变为颗粒状。经均匀化退火后, TiN的体积分数有所增加, 而平均尺寸却有所降低。再结晶退火的过程中有大量亚微米尺度的Ti(C, N)弥散析出, 其析出量随着熔体过热温度的升高而增加, 这些细小的Ti(C, N)粒子可以起到沉淀强化的作用, 提高690合金的显微硬度。
The optical, scanning and transmission electron microscopes have been used to investigate the effect of the melt superheating treatment (MST) on the microsturctures and Vickers hardness of of alloy 690. The results indicate that the volume fraction and average size of primary TiN decrease as the superheating temperature increases, and its morphology converts from regular blocky to granular. After homogenizing annealing, there is a slight increase in volume fraction of primary TiN, while a moderate decrease in the average size. Additionally, it is found that a great deal of sub-micron Ti(C, N) precipitates dispersedly during recrystallization annealing, and its amount increases with the superheating temperature. These sub-micron Ti(C, N) particles can improve the Vickers hardness of alloy 690 as the strengtheners.
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