Effect of annealing on the passive film stability and corrosion resistance of new families of iron-based amorphous metals

Abstract

Iron-based amorphous metals have incredible strength and hardness, and with the addition of alloying constituents, can also be formulated to have exceptional corrosion resistance. Compositions of several iron-based amorphous metals have been published, including several with very good corrosion resistance. The benefits of chromium, molybdenum, and tungsten on corrosion resistance has been previously studied and documented, however little is known about other alloying constituents and their effect upon devitrification and corrosion resistance. The compositions explored in this thesis research are the SAM40 base alloy and variations including systematic additions of nickel, yttrium, and titanium. Nickel is added to improve both mechanical properties and corrosion resistance. Yttrium is added to lower the critical cooling rate, thereby making the metallic glass easier to create and more stable once formed, thus improving the corrosion resistance. Adding titanium will enable the formation of an extremely stable protective titanium oxide film on the alloy's surface, which could enhance the corrosion resistance. Through xray diffraction and corrosion analysis, the effects of these alloy additions on the devitrification and corrosion resistance of this new class of amorphous metals have be quantified.