A calorimetric study of alloys along the Ti(Zn, Al)3 section

A calorimetric study of alloys along the section TiZn3-TiAl3 is carried out to determine their heat of formation (ΔfH∘) at 300 K using a high temperature direct drop calorimeter. The target compositions of the alloys lie in the range of 10-65 at.% Al. The structure and composition of the reacted samples are characterized by X-ray diffraction and electron probe microanalysis. The following values of ΔfH∘ (in kJ/mol-atom) at 300 K are obtained (by interpolation) for L12- Ti(Zn,Al)3 solid solution: −27±1 (at Ti25Zn65Al10), −30±1 (at Ti25Zn55Al20), −32±1 (at Ti25Zn45Al30), −34±1 (at Ti25Zn35Al40), −35±1 (at Ti25Zn25Al50) and −36±1 (at Ti25Zn15Al60). Calorimetric data are compared with the formation energy of L12- Ti(Zn,Al)3 alloys calculated from first-principles and sublattice cluster expansion, showing a very good agreement. Stabilization of L12- Al3Ti, by substituting Zn for Al, offers a potential to introduce it as strengthening precipitates in Al alloys.