Low-temperature relaxation processes in cold-worked zirconium

The internal friction and modulus relaxation spectrum of high-purity polycrystalline zirconium has been studied between 77 K and room temperature. Low (1 Hz) and high (50 kHz) frequency measurements are reported after room- and low-temperature tensile deformation. Three relaxation peaks appeared, called P₁, P₂ and P₃. The variation of these with the measuring frequency, amount of cold work and annealing of the specimen at temperatures above that of deformation was investigated. The peak P₁ appeared in the range 80 to 90 K at 1Hz after cold work at 80 K and dissappeared on heating the specimen above 200 K. P₂ appeared either after deformation at room temperature or at low temperature if followed by an annealing process above 200 K: this peak is a very wide one at low frequencies (1 Hz) with its maximum at about 150 K. P₃, generated by cold-working the specimen at 80 K, proved to be very unstable and recovered while being measured at 1 Hz: its physical origin is still uncertain. The recovery of the modulus defect after deformation at 80 K showed three stages, coincident with those of resistivity reported in the literature. The peak p₁ is considered to be due to the relaxation of dislocations against intrinsic lattice barriers, the peak P₂ to the interaction of point defects with dislocations.