Effects of grain size and microstructures on the internal friction and Young's modulus of a high-strength steel HT-80

Abstract

Effects of grain size and microstructure on internal friction and Young's modulus were investigated using a high-strength steel HT-80. The mechanism of the internal friction in the steel was discussed. The internal friction largely increased with decreasing grain size of specimens. This was attributed to the viscous flow at or in the vicinity of grain boundaries or phase boundaries. The internal friction of specimens with ferrite-pearlite structure was larger than that of specimens with sorbite structure at larger grain sizes, but the former was smaller than the latter at smaller grain sizes and larger strain amplitudes. These results suggested that the magneto-mechanical hysteresis loss also contributed to the internal friction of the steel, because the migration of the magnetic domain wall in the ferrite matrix was more difficult for the ferrite-pearlite structure. Internal friction also increased with increasing strain amplitudes. Young's modulus was large in both fine-grained and coarse-grained specimens for sorbite and ferrite-pearlite structures. This was related to the carbon concentration in the ferrite matrix.