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-The nature of the intermetallic layer which forms on the steel surface during immersion in typical galvanizing baths for galvannealed (GA) sheets production has been investigated on two commercial Titanium-stabilized Interstitial-Free (Ti-IF) steel substrates galvanized in baths with different Al contents. Results from this study show that in both cases the inhibition layer is biphasic and composed of a very thin Al-rich phase layer, identified as Fe 2 Al 5 Zn x , and a thicker Zn-rich phase layer on top of it, identified as δ. Experimental results also show that the Fe 2 Al 5 Zn x phase layer becomes discontinuous when decreasing the bath Al content. Discussions about the mechanisms of formation and the final microstructure of this inhibiting layer are also tackled in this paper by means of the Al-Fe-Zn ternary phase diagram at 460 • C and assumptions to justify any deviation from thermodynamic equilibrium are as well proposed.

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Several Nb based alloys (Nb-20Mo-15Si-25Cr, Nb-20Mo-15Si-25Cr-5B, Nb-20Si-20Cr-5Al, and Nb-20Cr-20Si-5Hf) have been prepared to evaluate the oxidation resistance from 700 to 1400°C in air. The phase identification was determined by calculating the isothermal sections in this temperature range using PANDATTM software. The experiments involve static heating for 24 hours (short term oxidation, STO) or 7 cycles of 24 hour heating (long term oxidation, LTO). Weight gain per unit area as a function of either temperature (STO) or time (LTO) has been used to determine their oxidation resistance. However, SEM, EDS on SEM, x-ray mapping, and XRD have been used to evaluate the oxide scale characterization and the influence of various microconstituent effects have been determined. It appears that B addition may be beneficial while Al is advantageous in comparison to Hf addition. The problem of pesting, typically, in a range of temperature from 900 to 1100°C needs to be controlled through minor additions since the alloys exhibit fairly good resistance at lower and higher temperatures up to 1400°C.