The effect of composition and stress on the selection of $\epsilon\to \tau$ transformation modes in MnAl-C

Abstract

The $\epsilon\to \tau$ transformation in MnAl-C alloys was studied by metallographic methods and by transmission electron microscopy. The product phase appears in two morphologies. A “flower-like” morphology results from a massive transformation whereas a “plate-like” morphology results from a shear reaction. The shear reaction appears preferentially in alloys with large amounts of Mn and C. Annealing under a suitable uniaxial compressive stress accelerates the operation of the shear mode