Metal matrix composites (MMC) containing TRIP‐steel/Mg‐PSZ were processed by cold pressing and conventional sintering in different atmospheres. The MMC was based on austenitic steel in the system Fe‐Cr‐Mn‐Ni showing transformation induced plasticity (TRIP). Depending on the sintering temperature, the sintering atmosphere and the steel composition the phase compositions of MgO partially stabilized zirconia (Mg‐PSZ) were analysed by scanning electron microscopy (SEM), energy dispersive X‐ray microanalysis (EDX) as well as electron backscatter diffraction (EBSD). The interactions between the alloying elements of austenitic stainless steel and the ceramic stabilizer (MgO) as well as the technological parameters lead to a significant change in the phase composition of the Mg‐PSZ. The changes can be analysed by EBSD due to the high spatial resolution.

The tensile and cyclic deformation behaviour of a new metastable austenitic stainless cast TRIP (TRansformation Induced Plasticity) steel and a composite material consisting of austenitic steel matrix (AISI 304) with 5% MgO partially stabilized ZrO2 (MgO‐PSZ) was studied in‐situ in a scanning electron microscope (SEM). In‐situ tests in the SEM show the evolution of the microstructure with the strain for uniaxial deformation and the number of cycles during fatigue, respectively. Initially, deformation bands develop. In these bands, the face‐centred cubic austenite transforms into the hexagonal ε‐martensite and subsequently to the body‐centred cubic α'‐ martensite. This evolution was studied by different SEM techniques. Electron backscatter diffraction (EBSD) was applied for phase and orientation identification. The dislocation arrangement was investigated applying the electron channelling contrast imaging (ECCI) technique to different deformation stages. The studies are completed with measurements of local displacement fields using digital image correlation (DIC).

Composite materials are up‐to‐date products in a growing range of applications and markets. Due to the advantageous combination of two or more materials new generations of materials can be generated. Closely linked to expanding variations of material combinations are increasing numbers of manufacturing techniques. The combination of ductile metals with hard and brittle ceramics offers a range of applications in the field of crash‐absorber and structural products with high mechanical load. This paper deals with the challenges of powder metallurgical processing of TRIP‐steel/Mg‐PSZ composite materials. The presented results are a contribution to improvements in plastic processing especially for lightweight honeycomb structures.

In the 1980 s the first stainless steel with TRIP effect was investigated intensively at the Institute of Iron and Steel Technology Freiberg. Hereby the basis for the newest developments was established. [1][2][3] Economic needs enforced the substitution of nickel with manganese in the stainless steels. Metal-ceramic composite materials have been investigated for several years. Within the framework of the Collaborative Research Centre 799 ''TRIP-Matrix-Composite'' metal matrix composites (MMCs) are created by combining ceramics with ductile metals. The combination of a ductile metal with hard and brittle ceramic offers a range of high strength and wear resistant materials. [4][5][6][7] MMCs are denoted by the ability of plastic deformation and high strain with reinforcements of ceramic particles. Zirconia (ZrO 2 ) appears in three modifications: between melting and 2 370 8C the cubic phase (c-ZrO 2 ) is stable. Further cooling leads to transformation into the tetragonal phase (t-ZrO 2 ) and below 1 170 8C highly distorted monoclinic ZrO 2 (m-ZrO 2 ) is thermodynamically preferred. There are a lot of overviews. [8,9] Phase transformations clearly could be shown by using TEM investigations. [10,11] The transformation of t-ZrO 2 to m-ZrO 2 appears with a volume change of 3-5% which exceeds critical fracture length in ceramics eliminating pure zirconia applications. By the addition of cations with related ions radius to zirconium the stabilization of high temperature phases to room temperature is possible. Traditionally additions of Y 2 O 3 , CaO, or MgO are used in construction and refractory ceramics. Depending on the processing route of high Mn austenitic stainless steel MMCs the contact time and temperature is varied resulting in a different phase composition of Mg-PSZ due to diffusion processes.

A metal matrix composite (MMC) consisting of AISI 304 austenitic stainless steel with up to 10 vol.‐% MgO‐PSZ was produced by a powder metallurgic process through sintering at 1300 °C and 1390 °C. The hot working of sintered samples was conducted between 900 °C and 1100 °C. The behaviour of softening kinetics was investigated using flow curve recording methods (dynamic softening) and the double‐hit method (static softening). The influence of the deformation parameters such as temperature, strain rate, inter‐pass time and relative density of the samples was determined. The microstructure development of the sintered composite after hot forming was determined by optical microscopy and SEM and was interpreted with the help of qualitative microstructure analysis. The results show a general acceleration of softening processes with increasing temperature and strain rate, with the addition of ZrO2 particles and a decrease in the density of composite materials. A mathematical‐physical model was developed to predict the softening behaviour and optimize the forming processes of the composite in the light of these results.