Polycrystalline 51.2at%N 27.6at%Mn and 21,1at% Ga bulk samples were quenched after annealing at 700°C, 800°C and 900°C for one hour. The parent phase, in sample quenched from 900°C, reveals the B2 structure whereas in the sample quenched from 700°C – the Heusler's structure L2
_{1}
. The ordering transformation was confirmed by the results obtained from high temperature DSC measurement. On a heating curve broad thermal peak appeared in the range between 700°C and 800°C. Increasing of the quenching temperature results in lowering temperatures of the martensitic transformation and simultaneously broadens its thermal range. Independently on the quenching temperature and the ordering of the parent phase the martensite shows the 10M structure type. However, in electron diffraction pattern, taken for the sample quenched from 800°C, additional effects of the diffusion electron scattering have been observed as a result of a short-range ordering caused by the Ni exceeding atoms.
