554.    CHEVENARD, P.  [Metallographic Interpretation of the Instability of Reversible Ferronickels.]  Compt. Rend., vol. 223, 1946, pp. 1074-1076; Chem. Abs., vol. 41, 1947, p. 3031.

                 Quenched ferro-Ni alloys show 2 stages of recovery.  The 2d, starting about 300°, is accompanied by graphite precipitation and severe contraction.  The 1^st stage is, in general, an expansion effect from room temperature to 175°, but elongation-time curves show a contraction preceding the expansion.  This is attributed to precipitation of cementite, favored by the Mn in the alloys, which subtracts Fe from the ferro-Ni and diminishes density.  To suppress the instability C should be held below 0.05%, remaining C should be stabilized with Ti or V, and the pieces should be treated before use to provoke all precipitation that can occur.