Abstract: Three kinds of AlTiC alloys with the mole ratio of Ti and C exceeding, equal to or below the stoichiometric value in TiC, i.e. Al-TiAl3-TiC, Al-TiC, and Al-Al4C3-TiC alloys, can be readily produced by a new method involving the simultaneous addition of Ti and C into Al melt. The latter two kinds of alloys have similar refinement efficiencies on pure Al despite of the presence of large amount of Al4C3 phase in Al-Al4C3-TiC, but their efficiencies are much lower than that of the first one due to the absence of excess Ti beyond the combined in TiC in the matrix, suggesting some significant role of excess Ti in the refinement. TiC phase in the alloys exists in the form of discrete particle or small clusters consisting of several discrete particles, which are homogeneously distributed in the matrix. Large agglomerates of TiC particles along grain boundaries were also observed. Al4C3 phase in Al8Ti3.5C is brittle and easy to react with moisture in the air. Analysis shows that formation of TiC is accomplished through the simultaneous reaction of Ti dissolved in the Al melt with either solid carbon particle or Al4C3 phase.
Al-Ti-C alloys with different phases prepared through reaction of Ti and C in Al melt
Abstract:
Three kinds of AlTiC alloys with the mole ratio of Ti and C exceeding, equal to or below the stoichiometric value in TiC, i.e. Al-TiAl3-TiC, Al-TiC, and Al-Al4C3-TiC alloys, can be readily produced by a new method involving the simultaneous addition of Ti and C into Al melt. The latter two kinds of alloys have similar refinement efficiencies on pure Al despite of the presence of large amount of Al4C3 phase in Al-Al4C3-TiC, but their efficiencies are much lower than that of the first one due to the absence of excess Ti beyond the combined in TiC in the matrix, suggesting some significant role of excess Ti in the refinement. TiC phase in the alloys exists in the form of discrete particle or small clusters consisting of several discrete particles, which are homogeneously distributed in the matrix. Large agglomerates of TiC particles along grain boundaries were also observed. Al4C3 phase in Al 8Ti3.5C is brittle and easy to react with moisture in the air. Analysis shows that formation of TiC is accomplished through the simultaneous reaction of Ti dissolved in the Al melt with either solid carbon particle or Al4C3 phase.
在Al 8Ti3.5C、 Al 8Ti2C、 Al 5Ti0.35C这3种合金中, Ti与C的摩尔比分别小于、 等于、 大于在TiC中的化学计量比4∶1。 图1所示是3种合金X射线衍射图, 显然3种合金基体中均生成了TiC物相, 除此之外Al 5Ti0.35C含TiAl3相, Al 8Ti3.5C中含Al4C3相。
Fig.5 Optical micrograph (a) of Al4C3 phase on fracture surface of Al 8Ti3.5C andX-ray diffraction patterns (b) of Al4C3 clusters (Arrows show some large clusters of this phase and there are still many small ones)
图6 未细化及用0.2%AlTiC合金细化后的纯铝宏观晶粒尺寸
Fig.6 Macro grain sizes of pure Al unrefined (a) and refined byAl 8Ti2C (b) , Al 8Ti3.5C (c) and Al 5Ti0.35C (d) at addition of 0.2%
图7 纯铝细化后的晶粒尺寸与不同AlTiC合金加入量的关系
Fig.7 Relationship of grain size ofpure Al with addition ofdifferent Al-Ti-C alloys