细晶TiAl基铸造合金的制备及其凝固特征

Synthesis and Solidification Characterization of TiAl Based Alloy with Fine Grain Structure

采用非自耗电弧熔炼铸造方法,制备了Ti-Al-Nb基铸造合金。通过X射线衍射、金相观察、扫描电镜及透射电镜等实验方法,研究了Al含量对基体合金显微组织与凝固特征的影响。结果表明,适当降低铸造合金中铝的含量,能制备出晶粒细小的Ti-44Al-2Nb-1Cr-1W-1B合金,其平均晶粒尺寸为50μm。细晶TiAl基铸态合金中β相与γ相存在'伴生'现象;同时,该合金中一定量β相稳定元素W和Nb的加入,使高温β相得以在凝固过程中保留到室温,这种少量β相的存在也限制了α相晶粒的长大。

Ti-Al-Nb based alloys were prepared by a non consumable skull melting. The effect of Al content on the microstructure and the solidification characterization of as-cast alloys were investigated using X-ray diffraction, optical microscope, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. It is shown that a fine grain structure Ti-44Al-2Nb-1Cr-1W-1B alloy with average grain size 50μm could be got by proper decreasing of Al content, and the companion phenomenon of co-existence of β and γ, phases in the fine grain structure as-cast alloy was found. Moreover, the proper additions of alloying elements such as W and Nb increased the stability of β phase, and thus β phase was retained to low temperature. The presence of β phase was found to restrict α grain growth at the temperatures above the α transus temperature