Mechanical Spectroscopy of Equal-Channel Angular Pressed Fe-Cr Alloys and Tungsten

Internal friction technique was used to investigate the microstructural stability of equal-channel angular pressed (ECAP) 9Cr1Mo steel (T91), Fe-18wt.%Cr alloy, and pure W. Several non-relaxation internal friction peaks are observed in three ECAP-strained specimens, which are related to the microstructural transition from a severely deformed state to a static recovery state of dislocations, and to recrystallized state. Along with the disappearance of the P 1 peak, another relaxation internal friction peak P 2 is observed during the second heating run only in Fe-18wt.%Cr alloy, and it does not disappear even during subsequent third heating run. This peak is not observed in T91 steel and W. The P 2 peak is likely associated with a process of grain boundary (Gb) sliding. Unlike T91, no abundant carbide precipitates distribute on Gbs to pin Gb and repulse Gb sliding, thus, the P 2 peak only occurs in Fe-18wt.%Cr alloy. It is concluded that high-temperature internal friction measurements are required to detect the grain boundary peak in pure W.

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