Cubic-to-monoclinic transformation mechanisms for CuZnAl

We review the cubic-to-monoclinic transformation mechanisms proposed in the literature for CuZnAl alloys; we confirm previous arguments and add new ones in favor of a 'DO3 -> 6M1' mechanism. We show that if the strain parameters satisfy a relation that allows for non-generic twinning in the monoclinic martensite, also extra habit planes exist, at which the twinned martensite can border the austenite. For special values of the strain parameters (and thus, probably, of the compositions in the alloy), preliminary results show that also wedge-shaped microstructures involving twinned martensite may exist.