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为寻找细晶组织的铸造ＴｉＡｌ基合金，在Ｔｉ－４４Ａｌ（ａｔ－％）和Ｔｉ－４８Ａｌ（ａｔ－％）两种Ａｌ含量的二元合金中添加了３Ｃｒ和６Ｃｒ（ａｔ－％）。结果表明，Ｃｒ对铸态α＿２＋γ合金的晶粒大小无明显的影响，但通过热处理可显著细化晶粒。对Ｔｉ－４４Ａｌ－３Ｃｒ和Ｔｉ－４８Ａｌ－３Ｃｒ合金分别采用１１５０℃、１６８ｈ和１２００℃、２４ｈ处理可取得最佳的细化晶粒效果，而且４８Ａｌ合金热处理后可更容易获得细晶组织。Ｃｒ促进有序富Ｃｒ相β＿２的形成，该相或者与片状α＿２相共生，或者分布于γ相的晶界，阻碍γ相长大。Ｃｒ在β＿２、γ＿２和γ相中的溶解度依次减少，它主要取代γ和α＿２相中的Ｔｉ，因而随着合金中Ｃｒ量增加，γ和α＿２相中的Ａｌ／Ｔｉ比增加。Ｃｒ还促使γ相内形成孪晶。
In order to find a fine grained cast TiAl-based alloy, 3Cr and 6Cr (at-%) were added to binary alloys containing two Al contents, Ti-44Al (at-%) and Ti-48Al (at-%). The results show that Cr has no obvious effect on the grain size of as-cast α_2 + γ alloy, but the grain size can be remarkably refined by heat treatment. The optimal grain refinement results were obtained for the Ti-44Al-3Cr and Ti-48Al-3Cr alloys at 1150 ℃, 168h, 1200 ℃ and 24h respectively, and the fine grain structure was obtained more easily after the heat treatment of 48Al alloy. Cr promotes the formation of ordered Cr-rich phase β_2, which coexists with sheet-like α_2 phase or distributes in the grain boundary of γ phase, hindering the growth of γ phase. The solubility of Cr in β_2, γ_2 and γ phase decreases in turn, which mainly substitutes Ti in γ and α_2 phase. Therefore, the Al / Ti ratio in γ and α_2 phase increases with the increase of Cr content in alloy. Cr also promotes the formation of twins in the γ phase.