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Published online by Cambridge University Press: 06 March 2019
The broadening of the (110)α and (220)α powder pattern peaks of bulk samples from the product of two commercial 70 ton heats of a 9Ni-4Co-0.45C alloy (HP 9-4-45) was studied by Fourier analysis. Both heats were heat treated to a variety of bainitic and tempered martensitic structures and the effective particle size and r.m.s. strain in the <110> direction were measured. Comparison of the mechanical properties with the parameters derived from the Fourier analysis suggests that neither the strain nor the particle size are controlling the strength or toughness. Strength increases with Strain while toughness decreases - both as expected. On the other hand, large particle size seems to favor greater toughness in contrast to the known effect of macroscopic (high angle boundary) grain size.
It is concluded that line shape analysis is a convenient method of investigation giving repeatable parameters which represent the transformation strains. The extension of this technique to these highly strained, metallurgically complex structures appears justified.