Microstructural study of an ODS stainless steel obtained by Hot Uni-axial Pressing

This study focuses on the consolidation of an ODS Fe-14Cr-1W-0.3Ti-0.3Y2O3 alloy obtained by powder metallurgy. The powder was sintered for 1 h at 1100 °C in a soft steel can and compacted by Hot Uni-axial Pressing (HUP) under 900 MPa within less than 5 s before air cooling. The HUPped material microstructure is prospected to determine relative density as well as microstructure and nano-precipitation. The HUP, which mimics the early stage of hot extrusion (HE), produces a fully dense metallurgical state. The HUPped microstructure is shown to be rather similar to the one obtained by HIPping for equivalent dwell time at high temperature. In both cases heterogeneous grain size microstructure was obtained. It is shown that the bigger grains come from static recrystallization occurring during the dwell time in furnace. Compared to HIP, the effect of the HUP is mainly to introduce intra-granular misorientations within these large recrystallized grains.