Investigation on point defect structure in single phase B2 type RuAl alloys by lattice parameter measurements

RuAl and its alloys. Part I. Structure, physical properties, microstructure and processing

“…For example, the equilibrium lattice constant calculated by the LMTO method [47] agrees good with the first published experimental values that seem to be less precise [2,74,75], while the LAPW method calculations [47] or the LAPW within a framework of the BSF method [56] agree better with recent experimental determinations [28,47,51,77]. Calculations using the LDA of the DFT resulted a in typical underestimation of the equilibrium lattice constant [45].…”

“…Ru-Al phase diagram calculated by CALPHAD technique [61], using modified sublattice model (MSL) formalism, showed reasonable match with the published phase diagrams. The recent study of a number of RuAl alloys made by PM (Ru 12c Al c ; 0:46 , c , 0:58 [28]) showed that the existence range of single-phase RuAl at room temperature differs from the previous results. X-ray diffraction (XRD) coupled with wavelength dispersive spectrometry (WDS) measurements revealed that RuAl extends from stoichiometry up to 46.2% Ru, which is in contrast with values in the literature that limit the room temperature existence of RuAl close to equiatomic composition [54,55,57,58].…”

“…Al), the lattice constant does not change since the solubility limit is exceeded and a second phase Ru(Al) appears in the microstructure coating RuAl grains. On the other side, the recent study [28] conducted on powder metallurgical samples, where a more precise composition control was obtained, shows an interesting trend of the lattice constant change (Fig. 5).…”

“…Table 3 summarizes the values of the lattice constant ðaÞ of RuAl, which is determined both experimentally [1,28,42, 47,51,74 -77] and by calculations [38,45,47,56]. Early reports in the literature [2,74,75] differ from recently published results [28,47,51,56,76,77] which indicate that values for the lattice constant gather around the value of 0.299 nm. For a number of arc-melted binary Ru -Al alloys, Fleischer [42] determined the lattice constant of RuAl and showed that the lattice constant decreases to stoichiometry (a ¼ 0:29916^0:00008 nm for stoichiometric RuAl).…”

“…The minimum value of the lattice constant (a ¼ 0:298844 nm) is observed in the stoichiometric RuAl, while in the Ru-rich direction the lattice constant increases up to a ¼ 0:29902^0:000067 nm (Ru 50.3 Al 49.7 ). For Al-rich compositions, the lattice constant of RuAl was also shown to increase up to a ¼ 0:29943^0:000097 nm (Ru 46.2 Al 53.8 ) according to the following equation [28]:…”