The deformation of Nb-Zr-N single crystals containing zirconium nitride particles - I. Mechanical properties

摘要

Two groups of Nb-Zr single crystals with different zirconium contents (up to about 1 at.% Zr) were made using an electron-beam floating-zone apparatus. Alloys containing ZrN dispersions were obtained by internal nitridation of Nb-Zr single crystals. The mechanical properties of the alloys were measured over the temperature range 4.2-373 K. All tests were carried out in compression using a testing machine with an integral helium cryostat. Differential tests were used to study the effect of the ZrN particles upon the thermal part of the flow stress. It was found that the overall strengthening of the materials was about 100 MPa and that probably only a fraction of this was due to the ZrN particles directly. The shapes of the stress-strain curves were similar to those of Nb-N interstitial alloys with negative hardening rates in most cases in contrast with the high hardening rates often observed in precipitation-hardened alloys. The thermal stress was very similar to that found in the pure metal and the results indicate that the fundamental deformation mechanism of niobium is not changed by the presence of the precipitates. [References: 14]