The plastic deformation and compression fracture of cylindrical samples of the bulk metallic glass Zr64.13Cu15.75Ni10.12Al10 have been studied in the temperature range 300–4.2K. The deformation curve at 300K is serrated due to the propagation of narrow shear bands. Catastrophic, uncontrollable fracture of samples, occurring as a result of the propagation of a macroscopic shear band with speed (of the order of 103m∕s) comparable to the sound speed, is observed at deformation ∼3–4%. When the temperature is lowered from 300 to 170 and 77K the deformation changes from serrated to smooth. An interesting low-temperature anomaly of the deformation process is found: “slow” (with speed of the order of 10−6m∕s) propagation of a single macroscopic shear band is observed at 170 and 77K. When the samples are cooled to 4.2K their macroscopic plasticity vanishes, and they undergo fracture, just as at 300K, as a result of the propagation of a catastrophic shear band with near-sound speed.
The mechanical properties under uniaxial compression of cylindrical samples of ultrafine-grain (UFG) zirconium (grain size ∼0.4μm) obtained by intense plastic strain (IPS)—a combination of extrusion, annealing, and drawing—have been studied in the temperature range 4.2–300K. The mechanical characteristics of UFG zirconium have been studied in two structural states and the results are compared with each other as well as with the characteristics of coarse-grain polycrystals of this material (state 1—samples after IPS, state 2—samples after IPS and annealing). It has been established that grain-size reduction under IPS substantially increases the yield stress of polycrystals (by a factor of 6 at 300K and by a factor of 4 at 77K) while maintaining a large reserve of plasticity up to 15%. Two stages of strain hardening and a decrease of the plastic-flow activation volume with increasing strain has been recorded in the strain diagrams of UFG zirconium. It is concluded that the main mechanisms determining the yield stress and strain hardening are the same for ultrafine- and coarse-grain zirconium: intragrain dislocation slip and twinning occur in parallel and interact with one another.
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