Thermoelastic martensitic transformations in ternary Ni$_{50}$Mn$_{50-z}$Ga$_{z}$ alloys

We have studied the effect of gallium alloying on the structure, phase composition, and physical properties of ternary alloys of the Ni$_{50}$Mn$_{50-z}$Ga$_{z}$ (0 $\le z \le$ 25 at %) quasi-binary section in a broad temperature range. Dependences of the type of crystalline structure of the high-temperature austenite phase and martensite, as well as the critical temperatures of martensitic transformations on the alloy composition, are determined. A phase diagram of the structural and magnetic transformations is constructed. Concentration boundaries of the existence of tetragonal $L$10 (2$M$) martensite and martensitic phases (10$M$ and 14$M$) with complex multilayer crystalline lattices are found. It is established that the predominant martensite morphology is determined by the hierarchy of packets of thin coherent nano- and submicrocrystalline plates with habit planes close to $\{011\}_{B2}$, pairwise twinned along one of 24 equivalent $\{011\}$ $\langle$01$\bar1\rangle_{B2}$ twinning shear systems.