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采用光悬浮炉在氩气环境下制备了成分为Nb-14Si-22Ti-2Hf-2Al-4Cr的定向凝固试棒,研究了凝固工艺对合金相组成、组织形貌和高低温力学性能的影响,并与电弧熔炼态的合金进行了比较。结果表明,定向凝固试样相组成与电弧熔炼态相比没有发生变化,均由Nb基固溶体(Nb solid solution,NbSS)和Nb/Si化合物Nb5Si3组成,定向凝固合金NbSS呈枝晶状,硅化物呈板条状沿着生长方向分布。与电弧熔炼态相比,定向凝固速度为15和10mm/h的合金在1250℃的抗压缩强度从电弧熔炼态的290MPa分别提高到约442和493MPa;15mm/h的定向凝固后,合金的室温断裂韧性从电弧熔炼态的12MPa·m1/2增加到15MPa·m1/2。通过光悬浮定向凝固法制备的该合金具有优良的高低温力学性能。
The directional solidification test bar with Nb-14Si-22Ti-2Hf-2Al-4Cr composition was prepared by using an optical suspension furnace under argon atmosphere. The influence of solidification process on the phase composition, microstructure and mechanical properties of the alloy was studied. And compared with the state of the arc melting alloy. The results show that the phase composition of the directionally solidified sample has no change compared with that of the arc melting state and is composed of a Nb solid solution (NbSS) and a Nb / Si compound Nb5Si3. The directional solidification alloy NbSS has a dendritic shape and a silicide Lined along the growth direction of the distribution. Compared with arc melting state, the compressive strength at 1250 ℃ of alloy with directional solidification speed of 15 and 10mm / h increased from 290MPa in arc melting state to about 442 and 493MPa respectively. After 15mm / h directional solidification, the room temperature The fracture toughness increases from 12MPa · m1 / 2 in the arc melting state to 15MPa · m1 / 2. The alloy prepared by optical suspension directional solidification has excellent mechanical properties at low and high temperature.