The main parameters of the microstructure of TRIP (TRansformation Induced Plasticity) composites with an austenitic matrix and a ZrO2 zirconium-dioxide reinforcing phase subjected to plastic deformation of different degrees (compressive uniaxial load) are studied by neutron diffraction and small-angle neutron scattering. A series of composite material samples with different contents of the ZrO2 ceramic phase (0, 10, 20, 30, and 100 wt %) are prepared by the powder metallurgy method using hot pressing. In the region of plastic deformation at load values above 650 MPa, two phases are observed in the austenitic matrix: cubic α'-martensite and hexagonal ε-martensite. Data on the lattice strains of the observed phases, dislocation density in the austenitic matrix, and characteristic sizes of the martensitic-phase particles are obtained.