The　crystallographic　mechanisms　of　the　crack　initiation　and　propagation　in　a　textured　polycrystalline　TiNi　shape　memory　alloy　were　studied　using　scanning　electron　microscope　and　ex　situ　electron　backscattered　diffraction　techniques.　The　results　indicated　that　stress-induced　martensitic　transformation　was　triggered　and　formed　a　sandwich　structure　at　the　front　of　the　crack　tip　prior　to　the　crack　initiation　in　the　polycrystalline　TiNi　alloy.　The　crack　propagated　intragranularly　and　occasionally　across　the　grain　boundaries.　The　closed　packed　planes　of　the　B2　parent　phase　such　as　{110}　and　{100}　were　revealed　to　favor　the　crack　propagation.　The　stress-induced　B2+B19(＇)　sandwich　structure　determined　the　crack　propagated　by　a　microscopic　sawtooth　pattern　and　therefore　a　ductile　feature　in　this　textured　polycrystalline　TiNi　sheet　specimen.　(c)　2007　American　Institute　of　Physics.