高温长时条件下TiAl合金与醋酸锆粘结氧化钇模壳的相互作用

Interaction between TiAl Alloy and Diacetatozirconic Acid-Bonded Yttria Mould under High-Temperature and Long-Term

针对TiAl合金定向凝固工艺要求,研究了高温长时条件下Ti-47Al-2Cr-2Nb合金熔体对醋酸锆粘接氧化钇模壳的侵渗作用和模壳对合金铸棒的污染状况。结果表明,醋酸锆粘结氧化钇模壳与Ti-47Al-2Cr-2Nb合金在1550,1600,1650℃下保温30min后,TiAl合金熔体的侵渗作用仅限于模壳内表层,模壳整体结构完整,未见合金液渗出。合金铸棒中存在两种夹杂物,一种是Al2O3,一种是由Al2O3和Y-Al-O组成的混合夹杂物。随着保温温度的升高,合金铸棒中夹杂物的尺寸和体积分数明显增加。1650℃保温30min条件下,夹杂物分布在合金铸棒的整个横截面上;1550,1600℃保温30min后,夹杂物从合金铸棒的边缘向中心呈减少趋势;1550℃保温30min条件下,铸棒中的夹杂物基本上仅分布在距边缘约500μm内,至铸棒表面2500μm处已基本没有夹杂物存在。文章对合金铸棒内部夹杂物的形成机理进行了分析。

The yttria mould with diacetatozirconic acid as binder was introduced for directional solidification of TiAl alloy. The infiltration of Ti-47Al-2Cr-2Nb （at%） molten metal on the mould was evaluated and the mould contamination on the metal-alloy rods was investigated. The results indicate that the infiltration of alloy occurs on the inner layer of the mould only and no structural damage or exudate is observed after holding 30 min at 1550, 1600, 1650℃, respectiw;ly. Two types of inclusions are explored in the alloy, they are Al2O3 and admixture inclusion composed of by Al2O3 and Y-Al-O and the scale and volume fraction of the inclusions significantly increase by rising of holding temperature. At 1650℃ for 30 min holding time, the foreign inclusions are distributed on the entire cross-section of the as-cast rod. The amount of the inclusions trend to decrease from the ,edge to the center of the rods at 1550, 1600℃ for 30 min Moreover, on the region around 2500 ktm to the surface of the as-cast rod at 1550℃for 30 min, no obvious ceramic inclusion is discovered. The forming mechanism of inclusions in the alloy was analyzed.