Formation and characterization of Al10CaFe2 compound in Al-Ca-Fe alloys
The phase diagram of the Al-Ca-Fe system in the aluminum corner,including the liquidus projection and solidification reactions,was studied by using thermodynamic calculations and experimental techniques.The results show that instead of the Al3Fe phase,a ternary compound whose composition corresponds to the formula Al10CaFe2 should be in equilibrium with the aluminum solid solution(Al).The transition from the binary to the ternary compound occurs via the peritectic transformation L+Al3Fe →(Al)+Al10CaFe2(at 638 ℃,3.3 at.％Ca and 0.5 at.％Fe).Primary and eutectic crystals of the ternary compound have a compact morphology,in contrast to needle-shaped inclusions of the Al3Fe phase.First principles calculations and X-ray diffraction analysis were used to determine the crystal lattice structure of Al10CaFe2 ternary compound.In addition,the near eutectic alloy Al-6wt.％Ca-1wt.％Fe after annealing at 500-600 ℃ has a fine structure with a total fraction of excess phases of about 25 vol.％.Thus,the Al-Ca-Fe system can be used to create new aluminum-matrix composite alloys.
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