〈001〉和〈011〉取向DD407单晶高温合金枝晶间距和微观偏析

DENDRITE ARM SPACINGS AND MICROSEGREGATIONS IN <001> AND <011> ORIENTATED SINGLE CRYSTAL SUPERALLOYS DD407

采用液态金属冷却(LMC)高温度梯度定向凝固炉制备<001>和<011>取向的DD407单晶高温合金,研究了晶体取向对枝晶间距和微观偏析的影响.结果表明,晶体取向对单晶高温合金的枝晶间距和微观偏析有明显的影响.枝晶间距随着<001>取向偏差角的增加而增加,但随<011>取向偏差角的增加而减小,且<011>取向的枝晶间距因为侧枝的分枝而明显大于<001>取向.成分分析表明,在不同取向的单晶中,Al,Ti和Ta富集于枝晶间,是正偏析元素,而W严重富集于枝晶干,为负偏析元素,当<011>取向平行轴向时元素的偏析程度最轻.

Single crystal superalloys DD407 with （001） and （011） orientations were produced with seeding technique by using the liquid metal cooling Bridgman furnace. The dendrite arm spacings （DAS） and microsegregations in the single crystal superalloys with （001） and （011） orientations were investigated. The results indicated that increasing the deviation angle from （001） orientation or decreasing the deviation angle from （011） would increase the dendrite arm spacing. In addition, DAS of single crystal grown along （011） orientation is obviously greater than that of （001） orientation for side-branching. EMPA results showed that the positive segregation elements A1, Ti and Ta enriched in the interdendritic region, and the negative segregation element W enriched in the dendrite core. The microsegregation in the single crystal with （011） orientation paralleled to the sample axis is the lightest. It is found that not only the DAS but the mechanism of dendrite evolution and arrayed pattern of dendrite affect the degree of microsegregation.