Martensitic phase transformation in Nb3Sn-x-ray observations

A compilation is presented of room temperature lattice spacing, ao, versus martensitic phase transformation temperature, Tm, of Nb3Sn for over 50 set of data including data of other investigations. The low temperature tetragonal phase transition occurs with c/a < 1 for aobetween 5.289 and 5.2933 Å, with c/a > 1 for aobetween 5.2865 and 5.2883 Å. Nb3Sn remains in the cubic phase (no transformation) for ao< 5.2865 Å and ao> 5.2933 Å, and for a very narrow region between 5.2883 Å and 5.289 Å. The effect of additives and the effect of matrix strain on the width of Tmis also discussed. A detailed tabulation is presented for the various Nb3Sn materials and their resultant transformation characteristics.