Twins in the B19' martensite of a shape memory alloy were investigated by using transmission electron microscopic and electron diffraction methods. Five twinning modes were observed. The <011> type-II twin predominated and was confirmed to be a lattice invariant shear. Most of the martensite variants involved <011> type-II twinning. The {111} type-I twinning could be classified into 3 types: deformation twin, variant accommodation twin and lattice invariant shear. The (100) and (001) compound twinnings were considered to be a deformation twin. The {011} type-I twinning was considered to be a lattice invariant shear, rather than a deformation twin, since it extended over an entire martensite plate.

M.Nishida, H.Ohgi, I.Itai, A.Chiba, K.Yamauchi: Acta Metallurgica et Materialia, 1995, 43[3], 1219-27