Correlation between internal friction background and the concentration of carbon in solid solution in a martensitic steel

A martensitic carbon steel was tempered in successive steps in order to vary the concentration of carbon in solid solution in the martensite. The actual solute content was assessed by thermoelectric power and X-ray diffraction. Internal friction was measured in a vibrating reed apparatus and in a torsion pendulum. The internal friction level around room temperature shows a surprising linear correlation with the carbon content even in the absence of the Snoek peak. This internal friction level is attributed to long-range interaction of edge dislocations with carbon in solid solution.