Preparation, Structure and Mechanical Properties of RuAl and (Ru,Ni)Al Alloys

Abstract

The intermetallic compound, RuAl with B2 CsCl type structure, has been shown to possess room-temperature toughness and plasticity. NiAl also forms a B2 compound and it is claimed that a pseudo-binary compound, (Ru,Ni)Al, may be formed because the difference in lattice parameter between the two binary phases is slight. In this work a study has been made of the mechanical properties of some polycrystalline compounds, across the RuAl-(Ru,Ni)Al pseudo-binary, prepared from high-purity elemental powders. Compressive yield stresses were measured between room-temperature and 900°C, and the mechanisms of plastic flow are discussed in relation to the dislocation structures observed by TEM. Hot-microhardness tests were made to provide an indication of the effect of solid-solution hardening.

Atomistic modeling of RuAl and (RuNi)Al alloys

“…In an effort to drive down both cost and weight and improve upon its other properties, several studies [4][5][6] have looked at alloying schemes for replacing Ru or A1 with other elements that generally form an isostructural B2 phase such as Co and Fe for Ru and Ti for AI. But by far, the most widely studied ternary alloying addition has been Ni [7][8][9][10][11][12][13]. Even then, there is disagreement as to the structure of ternary Ni-Ru-A1 alloys that exist between the NiA1 and RuA1 B2-phase fields.…”

Atomistic Modeling of Multicomponent Systems

“…To drive down cost and weight and improve upon its other properties, several studies [15][16][17][18] have looked at alloying schemes for replacing Ru or Al with other elements that generally form an isostructural B2 phase such as Co and Fe for Ru and Ti for Al. But by far, the most widely studied ternary alloying addition has been Ni, [19][20][21][22][23][24][25][26][27][28][29] although there is disagreement on the structure of ternary NiRu-Al alloys that exist between the NiAl and RuAl B2-phase fields. Some studies [21][22][23]25,[27][28][29] have reported a miscibility gap centered between the two binary phases resulting in a region consisting of two distinct B2 compounds, including a two-phase alloy at the composition Ni 25 Ru 25 Al 50 .…”

“…But by far, the most widely studied ternary alloying addition has been Ni, [19][20][21][22][23][24][25][26][27][28][29] although there is disagreement on the structure of ternary NiRu-Al alloys that exist between the NiAl and RuAl B2-phase fields. Some studies [21][22][23]25,[27][28][29] have reported a miscibility gap centered between the two binary phases resulting in a region consisting of two distinct B2 compounds, including a two-phase alloy at the composition Ni 25 Ru 25 Al 50 . [23] Many, but not all, of the ternary compounds seemed to exhibit two distinct components, but the evidence seemed to suggest coring as opposed to actual formation of two distinct B2 phases.…”

“…Some studies [21][22][23]25,[27][28][29] have reported a miscibility gap centered between the two binary phases resulting in a region consisting of two distinct B2 compounds, including a two-phase alloy at the composition Ni 25 Ru 25 Al 50 . [23] Many, but not all, of the ternary compounds seemed to exhibit two distinct components, but the evidence seemed to suggest coring as opposed to actual formation of two distinct B2 phases. [24] Furthermore, a sample within the miscibility gap was heavily milled and annealed so that diffusion distances would be much smaller and a better opportunity for obtaining a near equilibrium structure would exist.…”

“…Reported measurements [23,24] of a(x) are also considered as having a linear behavior. The linear fit of the experimental values [23] (normalized to the equilibrium B2 value a 0 ) is a(x)/a 0 = 1)0.0006949 x. In spite of the slight positive deviation from linearity, the best linear fit of the BFS prediction is almost identical, a(x)/a 0 = 1)0.0007266x.…”