以球形的预合金粉末 Ti-45Al-8.5Nb-0.2B-0.2W-0.1Y和元素混合粉 Ti+45%Al+10%Nb(%,原子分数)作为原料,研究了凝胶注模成形和氩气烧结制备高Nb-TiAl 合金的工艺。研究结果表明球形的预合金粉悬浮液浆料流变性良好,其悬浮液固相含量最高达70%(体积分数),经过凝胶注模体系成形干燥后的坯体在1480℃氩气气氛下烧结2h 后,烧结体相对密度达到99.1%,而元素混合粉的固相含量只有50%(体积分数),烧结体的相对密度为85.5%。通过X射线衍射分析和扫描电镜观察表明,以预合金粉为原料得到的样品主要成分是γ-TiAl 和β-Ti2 Al,以元素粉为原料得到的样品主要成分是γ-TiAl,并含有少量的α和β相,其组织是近片层。高 Nb-TiAl 合金的预合金粉末经凝胶注模成形和烧结后,可获得组织均匀的高致密度合金,其抗压强度为1715MPa,相对压缩率为1.85%。
High Nb-TiAl alloys were prepared by gelcasting method and sintering in argon atmosphere from Ti-45Al-8.5Nb-0.2B-0.2W-0.1Y spherical prealloyed powder and mixed element powders Ti+45%Al+10%Nb (at%).The results show that the slurry of spherical prealloyed powder has better rheological properties,and the solid loading of former slurry was up to 70 vol%.The dried bodies using the non-aqueous system gelcasting were sintered at 1480℃ for 2 hours in argon atmosphere.The relative density of sample with solid loading at 70 vol% from prealloyed powder reaches to 99.1%,much higher than relative density 85.5% of the mixed element powder (solid loading at 50 vol%).The microstructure of the sintered high Nb containing TiAl was analyzed by using electronic microscopy (SEM)and X-ray diffraction (XRD).The results show the sample from prealloyed power consists mainly ofγ-TiAl andβ-Ti2 Al;the element power was mainly composed ofγ-TiAl and a small a-mount ofαandβwith fine lamellar microstructure.After the prealloyed powders were gelcasting and sintered at 1480℃ for 2 hours,high Nb-TiAl alloys with high density and fine microstructure could be obtained and with the compressive strength of 1715MPa and the relative compressive ratio of 1.85%.
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