The thermochemical behavior of some binary shape memory alloys by high temperature direct synthesis calorimetry

The standard enthalpies of formation of some shape memory alloys have been measured by high temperature direct synthesis calorimetry at 1373 K. The following results (in kJ/mol of atoms) are reported: CoCr (−0.3 ± 2.9); CuMn (−3.7 ± 3.2); Cu3Sn (−10.4 ± 3.1); Fe2Tb (−5.5 ± 2.4); Fe2Dy (−1.6 ± 2.9); Fe17Tb2 (−2.1 ± 3.1); Fe17Dy2 (−5.3 ± 1.7); FePd3 (−16.0 ± 2.7); FePt (−23.0 ± 1.9); FePt3 (−20.7 ± 2.3); NiMn (−24.9 ± 2.6); TiNi (−32.7 ± 1.0); TiPd (−60.3 ± 2.5). The results are compared with some earlier experimental values obtained by calorimetry and by EMF technique. They are also compared with predicted values on the basis of the semi empirical model of Miedema and co-workers and with ab initio calculations when available. We will also assess the available information regarding the structures of these alloys.

Research highlights
► We studied 14 shape memory alloys.
► The enthalpies of formation and structure characteristics are summarized.
► Theoretical predictions by ab initio calculations compare better with experimental measurements than Miedema's semi empirical model.