Microstructure and mechanical properties of Al containing ODS ferritic alloys by VHP and HIP

A new Al containing oxide dispersion strengthened (ODS) ferritic alloy Fe-14Cr-3Al-2W-0·1Ti-0·35Y₂O₃ (wt-%) (14Cr-ODS) was produced by mechanical alloying, followed by vacuum hot pressing (VHP) at 1100°C for 1 h under 35 MPa, and hot isostatic pressing (HIP) at 1160°C for 3 h under 130 MPa. The microstructure and tensile properties of the two kinds of alloys were investigated. TEM studies indicate that the ODS alloys exhibit the characteristic ferritic structure containing Y-Al-O nanoparticles. Tensile characterisation at room temperature has shown that the tensile strengths of 14Cr-ODS alloy after VHP and HIP are 1312 and 968 MPa respectively. After HIP for 3 h, the 14Cr-ODS alloy has much lower tensile strength. However, the ductility of the 14Cr-ODS alloy after HIP is twice as large as that after VHP. The mechanical properties have close relations with the size of nanoparticles and microstructure of the ODS alloy. The size of the oxide nanoparticles and the grain size of the matrix of the ODS alloy after VHP are smaller than those after HIP.