Elastic constants and internal friction of martensitic steel, ferritic-pearlitic steel, and α-iron
Sudook A. Kim, Ward L. Johnson
The elastic constants and internal friction of induction hardened and unhardened SAE 1050 plain-carbon steel were determined by acoustic resonance spectroscopy. The hardened specimen contained only martensite and the unhardened specimen was ferrite-pearlite. Using an inverse Ritz algorithm under the assumption of orthorhombic symmetry, all nine independent elements of the elastic-stiffness tensor were determined, and from the resonant peak widths, all nine elements of the internal friction tensor were determined. Similar measurements and analysis on monocrystalline α-iron were performed. The steel was found to be only slightly anisotropic, and the isotropically approximated elastic constants were lower in the martensite than in ferrite-pearlite: shear modulus by 4 %, bulk modulus by 1 %, Young modulus by 3 %, and Poisson ratio by 1.5 %. Isotropically approximated elastic constants and Poisson ratio of ferrite-pearlite and α-iron were similar. All elements of the internal friction tensor in martensite were higher than those of ferrite-pearlite, but lower than those of α-iron.