Effect of sintering temperature and aluminium addition on thermal stability, micrographic features, and mechanical properties of Fe-Ni based ODS alloys

Abstract

In the present study, effects of titanium (Ti) and Ti+aluminium (Al) addition have been investigated on thermal stability and mechanical behaviour of Fe-42 wt% Ni-2 wt% Y2O3-X (X = Ti, Ti+Al) alloys. Accordingly, Fe-42 wt% Ni-2 wt% Y2O3-2 wt% Ti (2Ti), and Fe-42 wt% Ni-2 wt% Y2O3-2 wt% Ti-2 wt% Al (2AlTi) compositions were prepared through mechanical alloying followed by spark plasma sintering (SPS) at 1050 & 1100 °C. The sintered 2Ti alloy resulted in a huge grain coarsening (1815 nm) in contrast to the 2AlTi alloy sample (av. grain size 441 nm) sintered under same condition (1100 °C). Correspondingly, mechanical properties of the 2AlTi alloy found to be much superior (hardness-5.1 GPa, compressive yield strength-1075 MPa) to that of the 2Ti sample (hardness-3.6 GPa, compressive yield strength-580 MPa). Strengthening mechanisms analysis confirmed that the superior mechanical properties are attributed mainly to the grain boundary hardening (because of ultrafine matrix grains) and dispersion strengthening (due to the evolution of greater amount of nanosize complex dispersoids in the 2AlTi alloy). The experimental compressive strength properties were validated with simulated compression test data generated through the FE method. Barrelling effect due to the compression loading is compared and correlated with the FE-simulated data.