Cr depletion of the second phase particles in a Zr-Sn-Nb-Fe-Cr alloy: A TEM and SIMS study

Transmission electron microscopy (TEM) and Secondary Ion Mass Spectroscopy (SIMS) were used to investigate the microstructural and chemical evolution in a zirconium alloy processed by high pressure torsion (HPT) under 4 GPa at room temperature. Results showed that the grain sizes were significantly reduced and no α to ω phase transformation was detected after the HPT processing. A new phenomenon of which the Cr atoms diffused from the second phase particles (SPPs) to the zirconium matrix was confirmed. Further TEM analysis indicated that a large number of dislocations were generated especially in the vicinity of the SPPs. The possible mechanisms for the absence of the α to ω phase transformation and the Cr depletion of the SPPs were discussed.