中文摘要：

研究了Nb-S i-Ti-H f-Cr-A l-B-Y合金在电子束区熔炉上的定向凝固组织、室温断裂韧性和高温瞬时拉伸性能。合金的组织主要由Nb基固溶体(Nbss)、α-(Nb)5S i3和(Nb)3S i相组成。定向凝固后,初生Nbss枝晶以及Nbss+α-(Nb)5S i3/(Nb)3S i层片状或棒状共晶团均沿着试棒轴线定向排列。当电子枪移动速率R=2.4 mm/m in时,定向效果最好。定向凝固使合金在1250℃的拉伸强度及室温断裂韧性均显著提高。R=2.4 mm/m in试棒的抗拉强度最高,达85.0 MPa,同时其室温断裂韧性也达到19.4 MPa.m1/2。

英文摘要：

The microstructure and mechanical properties including room temperature fracture toughness K_q,tensile strength σ_b and elongation δ at 1250℃ of the Nb based alloy directionally solidified in an electron beam floating zone melting(EBFZM) furnace have been evaluated.The microstructure was primarily composed of Nb solid solution(Nbss),α-(Nb)_5Si_3 and(Nb)_3Si phases.After directional solidification with the moving rate of electron beam gun R being respectively 2.4,4.8 and 7.2 mm/min,the primary Nbss dendrites...