定向凝固过程中Ti-47Al-2Cr-2Nb合金与Y_2O_3陶瓷的相互作用

INTERACTION BETWEEN Ti-47Al-2Cr-2Nb ALLOY AND Y_2O_3 CERAMIC DURING DIRECTIONAL SOLIDIFICATION

本文研究了定向凝固条件下Ti-47Al-2Cr-2Nb合金与Y_2O_3/Al_2O_3双层结构陶瓷管内层Y_2O_3的相互作用.结果表明,Y_2O_3层有效地阻隔了化学稳定性较差的Al_2O_3外层与TiAl合金熔体的接触,从而避免了Al_2O_3与TiAl之间的化学反应.合金铸棒内含有平均体积分数约为0.14%的少量Y_2O_3夹杂物,主要是由于在定向凝固实验初期阶段Y_2O_3陶瓷在受到流动的合金熔体渗透侵蚀后脱落所致,对持续时间不敏感.高温下合金熔体促进了Y_2O_3陶瓷表层的再烧结并形成了2—10μm致密的阻挡层,从而阻止了合金熔体向Y_2O_3陶瓷内部的进一步渗透以及内部未完全烧结Y_2O_3陶瓷颗粒向合金熔体中的继续脱落.

Interaction between Ti-47Al-2Cr-2Nb alloy and inner layer Y_2O_3 of Y_2O_3/A1_2O_3 double-layer ceramic tube has been investigated during directional solidification.The results show that the Y_2O_3 layer effectively prevents the chemical reactions between TiAl alloy melt and exterior layer Al_2O_3 with lower chemical stability by blocking their direct contact.The DS alloy ingot contains Y_2O_3 inclusions which mainly come from the shedding of Y_2O_3 from ceramic tube inwall by being penetrated and eroded by fluid alloy melt in the initial phase of the directional solidification test.The average volume fraction of the inclusions is only about 0.14%and is insensitive to time.The re-sintering of the Y_2O_3 ceramic surface layer occurs and a 2—10μm dense barrier layer is formed by dint of alloy melt at high temperature.It prevents further pervasion of alloy melt into the Y_2O_3 ceramic and shedding of imperfectly sintered Y_2O_3 particles into the alloy melt.