Influence of titanium on nano-cluster (Y, Ti, O) stability in ODS ferritic materials

The addition of titanium is well known to refine the precipitation of nano-phases (Y, Ti, O) in oxide dispersion strengthened (ODS) ferritic materials. In order to understand the influence of titanium on the nano-cluster nucleation, two powders of ferritic materials Fe–18Cr–1W were mechanically alloyed with a nano-powder of yttrium oxide Y2O3 in a planetary mill, one without titanium and one with 0.8 wt% of titanium. Several analyses were conducted by small angle neutron scattering (SANS) on powders after different milling conditions and heat treatments. The SANS technique appeared to be extremely useful to follow the precipitation of the nano-phases in ODS ferritic materials. The analysis of these tests indicates that the role played by titanium is clearly observed during the reprecipitation of the nano-oxides though the effect of titanium on the oxide dissolution during the milling is not obvious. Titanium is usually considered to refine the precipitation in ODS materials. This study shows that the nano-phases formed in powders with some titanium are much more resistant to the coarsening than the phases formed without titanium.