Abstract
Changes in internal friction at room temperature of a low Cr-Mo alloy steel which has excellent resistance to tempering and low tendency to tempering brittleness were investigated together with changes in mechanical properties and micro-structures.
Internal friction was measured in terms of free decay of transversal resonance vibration which was caused in a specimen by the electro magnetic method.
Experimental results are as follows:
(1) Excellent toughness and smallest value of strain amplitude independent internal friction are observed with specimen tempered at about 700°C after quenching. This is probably due to uniform distribution of fine carbides and pinning-down effects of dislocations.
(2) A martensite structure has not strain amplitude dependent internal friction.
