Ductile fracture of mechanically alloyed iron-yttria alloys

The influence of Y203 particle content on the tensile fracture of mechanically alloyed iron has been studied for a series of dispersion-strengthened alloys containing up to 10 vol pct particles. When compared to the behavior of spheroidized steels, the present results indicate that at comparable volume fractions of particles, the Fe-Y203 alloys exhibit a much decreased tensile ductility. Observations of microscopic damage indicate that this is a consequence of rapid void nucleation at small strains, limited void growth, and enhanced void linking, especially at high particle contents. Analysis of these observations suggests (a) a surprisingly high oxide particle-matrix interfacial bond strength, (b) an influence of rapid strain hardening at small strains in creating high flow stresses, which assist void initiation, (c) enhanced void nucleation at high volume fractions of particles due to neighboring particles and voids, and (d) an accelerated void-linking process at high volume fractions of particles when interparticle spacing approaches particle/ void size.

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