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采用定向凝固真空电阻炉装置,成功制备了Ti-48Al-6Nb-1Cr合金定向凝固试样,观察了不同抽拉速率下的过渡区、稳态区组织,以及固-液界面形貌。结果表明,当抽拉速率为5μm/s时,合金界面以胞状树枝晶生长,全片层组织(γ+α2)与生长方向几乎全部成45°夹角,合金凝固时的析出相为β相;当抽拉速率增加到25μm/s时,合金界面为明显的树枝晶生长,在初始生长区全片层组织方向与生长方向成0°和45°夹角,随着凝固的进行,组织中与生长方向垂直的片层组织所占比例增加,达到稳定区时,其夹角几乎全变为90°,说明析出相在25μm/s时开始由β相向α相发生转化;当抽拉速率达到50μm/s时,析出相几乎全部以α相生长;而且随着抽拉速率的增加,二次枝晶间距与片层间距减小,组织得到细化。
The directional solidification samples of Ti-48Al-6Nb-1Cr alloy were successfully prepared by directional solidification vacuum resistance furnace. The transition zone, steady zone structure and solid-liquid interface morphology were observed under different drawing rates. The results show that when the pull rate is 5μm / s, the interface of the alloy grows with dendritic dendrites and the total lamellar structure (γ + α2) forms an angle of 45 ° with the growth direction. The precipitation phase of the alloy is β phase When the pull rate was increased to 25μm / s, the interface of the alloy was obviously dendrite growth. The orientation of the whole slice in the initial growth zone was at 0 ° and 45 ° with the growth direction. With the solidification proceeding, The proportion of lamellae perpendicular to the growth direction increased. When reaching the stable zone, the included angle became nearly 90 °, which indicated that the transformation fromβphase toαphase started at 25μm / s. When the extraction rate reached At 50μm / s, almost all of the precipitated phase grows in the α phase. With the increase of the drawing rate, the secondary dendrite spacing and the spacing between layers decrease, and the microstructure is refined.