Research on Mediate Temperature Decomposition of High Nitrogen Austenite

The decomposed products from high nitrogen austenite aging at 225°C were investigated by TEM. It is found that the shape of decomposition products inside the austenite grains is not regular and not strictly oriented. Preferential nucleation of y-Fe4N at dislocations and grain boundaries has been observed. It also has been found that during the first stage of the high nitrogen austenite decomposition a large quantity of ultra-fine /-Fe4N precipitate inside the parent austenite, which has been thought to be the undecomposed region before. The ultimate products are composed of highly dispersed a-Fe and /-Fe4N, with both of them maintaining nanometer scale. The micro-hardness of them can be as high as 900HV.