2009 Volume 49 Issue 9 Pages 1432-1435
Complete set of elastic constants Cij of α-Fe single crystal have been investigated from ambient temperature up to 893 K by electromagnetic acoustic resonance. Longitudinal component of elastic constants C11 showed linear temperature behavior and the magnitude of elastic softening was approximately 13%. The remainning two shear moduli, C44 and C′, however showed highly nonlinear behaviors with significant softenings of 50%. On a Blackman diagram, elastic constant ratios at high temperatures move to a limit, C12/C11=1 and C44/C11=0, where Born's two lattice instability criteria have been satisfied simultaneously. Violation of Cauchy relation is also significant upon heating.