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Within the Collaborative Research Center 799 novel composite materials which consist of a highly alloyed TRansformation-Induced Plasticity/Twinning-Induced Plasticity (TRIP/TWIP) CrMnNi cast steel matrix and a partially stabilized zirconium dioxide (Mg-PSZ) ceramic, referred to as TRIP-Matrix-Composites, are developed. [1] By applying an external load larger than the yield strength, the TRIP steel matrix shows a strain-induced phase transformation from metastable austenite to a 0 -martensite which leads to a concurrent increase of strength and ductility. By contrast, stress-induced formation of a 0 -martensite occurs at stresses below the yield strength, i.e., during elastic deformation. [2] The stress-induced transformation of the partially stabilized ZrO 2 from tetragonal phase to monoclinic modification can result in a further increase of the strength. Currently the interstitial-free austenitic CrMnNi cast stainless steels with TRIP/TWIP effect are in use. Representative alloys are 16Cr-7Mn-3Ni, 16Cr-7Mn-6Ni, and 16Cr-7Mn-9Ni. [3,4] These austenitic steel grades typically show low yield strengths of the order of 180-200 MPa. As a result of the low stress levels, only small fractions of the ceramic phase can transform to the monoclinic structure. In order to assist the phase transformation of the ceramic phase from tetragonal to monoclinic, the current steel research in the CRC 799 is focused on the increase of strength, especially the yield strength of the austenitic TRIP/TWIP CrMnNi cast steels by solid solution strengthening by nitrogen. Furthermore, the reduction of delta ferrite volume fractions, the adjustment of a pronounced TRIP/TWIP effect at operating temperatures and improved resistance against the intercrystalline corrosion by the addition of nitrogen is desired. In recent years, highly alloyed TRIP and TWIP steels have received much attention in both academia and industry because of their superior mechanical properties. [5][6][7]12] The high-manganese TWIP steels can be divided in the alloying systems FeMnC and CrMnC with additions of the main alloying elements such as N, Al, Si. In these steels g ! e transformation and deformation-induced twinning can appear in dependence of the SFE of the austenite. It is commonly believed that stacking fault energies below 18-20 mJ m À2 favor the g ! e phase transformation and higher values favor the twinning of austenite. [8][9][10] The longest known FeMnC steels are characterized by manganese contents between 15 and 30% and an austeniticThe effect of the manganese content (0-11%) on the transformation temperatures, the mechanical properties and microstructure development of five highly alloyed 14Cr-XMn-6Ni cast stainless steels with 0.1% nitrogen was studied. The examinations reveal that the M s , A s , and A f temperatures decrease with increasing manganese contents. As a result of low austenite stability, room temperature austenitic-martensitic as-cast microstructure was formed at manganese contents between 0 and 3%. At manganese levels of 6% and higher a fu...

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