Phase equilibria and microstructure evolution of Al–Mo–Ti ternary alloys

Thermodynamic assessment of the Al–Mo system and of the Ti–Al–Mo System from 0 to 20at.% Ti

“…Based on the results of metallographic analysis and DTA, partial isothermal sections from 0 to 20 at.%Ti at 1673, 1573, 1540, 1473, and 1373 K, as well as an isopleth through 50 at.%Al from 0 to 20 at.%Ti were constructed. It was also concluded that the transition reaction b þ Al 8 Mo 3 / d þ h should take place at z1540 K. The results of Nino et al [15] also confirmed that the b phase is continuous in the solid state solution from the TieMo binary to the AleMo binary since an alloy of composition 3 at.%Tie52 at.%Ale45 at.%Mo, with only 3 at.%Ti, showed a single phase b microstructure following heat treatment at 1773 K and quenching [15].…”

“…Contrary to the work of Nino et al [15], the AlMo and b phases were not considered to form a continuous solid solution in the assessment of Tretyachenko [60]. Instead, the assessed 1873 K isothermal section shows a two phase AlMo þ b field with a maximum solubility of Ti in AlMo of z3 at.%Ti.…”

“…However, calculations using this dataset cannot reproduce the phase equilibria determined by Nino et al [15] such as: (1) the continuity of the b phase to the AleMo binary at 1773 K and 50 at.% Al, (2) the b phase solidification of several alloys with Ti compositions from 15 at.% Ti to 17 at.% Ti and Al compositions from 47 at.% Al to 50 at.% Al, and (3) the transition reaction b þ Al 8 Mo 3 / d þ h at 1540 K. In fact, the calculations show that such phase equilibria can only be reproduced if the AlMo phase in the AleMo binary melts congruently [16]. This result confirms the experimental work of Rexer [17], who showed the congruent melting of AlMo by metallographic investigation and thermal analysis of various alloys in the AleMo system.…”

“…There is no information on the solubility of Ti in the Al 12 Mo, Al 5 Mo, Al 22 Mo 5 , Al 17 Mo 4 , Al 4 Mo, and Al 63 Mo 37 binary AleMo phases, but there is evidence in the literature that the Al 8 Mo 3 and d-AlMo 3 phases dissolve Ti. For example, the equilibrium b þ Al 8 Mo 3 þ d-AlMo 3 tie-triangle data for an alloy of composition 3 at.%Tie52 at.%Ale45 at.%Mo, which was heat treated at 1673 K and quenched, showed that the Al 8 Mo 3 phase dissolved 1 at.%Ti and that the d-AlMo 3 phase dissolved 2.7 at.%Ti [15].…”

“…The s phase forms through a peritectoid reaction at z1523 K [60]. Nino et al [15] published the most comprehensive work on the phase equilibria in the TieAleMo system from 0 to 20 at.%Ti. Several samples with Al contents ranging from 45 to 55 at.%Al and Ti contents ranging from 3 to 17 at.%Ti were heat treated at 1773, 1723, and 1673 K and quenched.…”