Partition behavior of alloying elements and phase transformation temperatures in Co–Al–W-base quaternary systems

γ′ Phase Stability and Phase Equilibrium in Ternary Co-Al-W at 900 °C

“…[2,[7][8][9] Other work has focused on the mechanical properties of ternary and higher order alloys, [10][11][12][13][14][15][16][17] the evolution and coarsening behavior of two-phase c-c¢ microstructure, [13,15,[18][19][20] or the microstructure and partitioning behavior of quaternary and higher order alloying elements. [13,15,[21][22][23][24][25] Furthermore, the only experimental data available for temperatures other than 900°C are the 1000°C isothermal section presented by Sato et al [1] and data reported by Xue et al at 1300°C. [6] If the development of new high temperature alloys based on the Co-Al-W ternary system is to be realized, an accurate understanding of the thermodynamics and phase equilibria of the system is essential as the foundation for building useful thermodynamic databases for alloy design and discovery.…”

Creep behavior of a novel Co-Al-W-base single crystal alloy containing Ta and Ti at 982∘C

“…It was in general consistent that γ solvus temperature was significantly increased by Ta, Ti and Nb additions, and reduced by Fe and Cr additions to different extents, whereas controversial results were observed in quaternary alloys with the additions of Mo and V [6][7][8][9]. Later, several alloys with more complex compositions were developed, and further improvement in γ solvus temperature was evident in certain alloys [9].…”

“…Alloying elements Ta and Ti, with an atomic radius relatively larger than Co, were experimentally determined to preferentially partition into γ phase [7], which in turn should possess an higher lattice constant than γ phase. Similar to the chemical composition of the present alloy TaTi, Pollock and coworkers also utilized the partition behavior of Ta and Ti on the purpose to yield the positive misfit in Ni-base superalloys PWA at high temperature [13].…”

“…For an attempt to increase the γ solvus temperature, which was highly responsible for improving high temperature strength in γ -γ two-phase alloys, various alloying additions have been investigated in Co-Al-W-base alloys [6][7][8][9]. It was in general consistent that γ solvus temperature was significantly increased by Ta, Ti and Nb additions, and reduced by Fe and Cr additions to different extents, whereas controversial results were observed in quaternary alloys with the additions of Mo and V [6][7][8][9].…”

“…Later, several alloys with more complex compositions were developed, and further improvement in γ solvus temperature was evident in certain alloys [9]. However, the detrimental microstructural stability by the formation of secondary phases that enriched in refractory alloying elements was observed among most of these alloys due to the very narrow γ -γ two-phase region [4,[6][7][8]. It appeared that only quaternary alloys containing Ta or Ti promoted microstructural stability, in addition to higher γ solvus temperature [4,[6][7][8].…”