Low-temperature mechanical properties of thoria dispersion-strengthened iron

The mechanical properties of iron, and iron containing a thoria dispersion in volume fractions of 0.9 and 1.7 pct, have been determined over the temperature range 77 to 373 K. Yield stress values for Fe-ThO2 calculated from a modified Orowan relation were within 8 pct of the experimental values. A peak in work hardening rate was observed in the temperature range 250 to 300 K. The peak occurred at each of the selected strains, 1, 2, 4, and 8 pct, and in all three materials. The work-hardening rates of the thoriated alloys remained roughly double that of iron at all strains. The particles were considered to increase the rate of dislocation multiplication, and have a strong but largely indirect effect on the work-hardening process.