TiAl-10Nb合金铸态组织演化规律的研究

The study on the as-cast microstructure evolution of TiAl-10Nb alloys

研究Ti-(44～54)Al-10Nb合金铸态组织的演化规律,并确定全β凝固的TiAl-10Nb合金的成分范围。实验结果表明:Ti-(44～53)Al-10Nb合金的凝固组织为典型的柱状晶组织,Ti-54Al-10Nb合金的宏观组织为等轴组织;在其凝固组织(纵截面)上部存在较多的缩松,这主要是由于Nb元素的添加量加多,从而使TiAl基合金熔体的粘度增加,在冷却过程中熔体中产生的气泡不能排除所造成;与TiAl二元合金相比较,Nb元素的加入扩大了β相的凝固范围,TiAl-10Nb合金的全β凝固的成分临界点为50at.%Al,即Al含量小于50at.%时TiAl-5Nb合金是以全β凝固方式进行的。

In the paper, the as-cast microstructure evolution of Ti-（44-54）Al-10Nb alloys was investigated, and then the content region of full beta solidification was determined. The results show that the solidification structures of Ti-（44-53）Al-10Nb alloys are the type columnar structure. The macrostructure of Ti- 54Al-10Nb alloy is equiaxed structure. It is found that a lot of the shrinkage cavity in the macrostructural top of TiAl-10Nb alloys, because Nb additions induce that the melt viscosity increases. Thereby, a lot of the air bubbles can not completely escape from the melt during the cooling process. Compared with TiAl binary alloys, Nb additions enlarge the 13 phase solidification region. The critical value of full β solidification is 50 at. %Al for TiAl-10Nb alloys, that is to say, the solidification of TiAl-10Nb alloys is full β solidification when A1 contents less than 50 at. %. Key words：TiAl-10Nb alloy; primary phase; full β solidification; microstructure evolution