High temperature hardness testing of δ-zirconium hydride: Yield stress estimation by analytical and numerical models

The mechanical properties of δ -zirconium hydrides were studied using a combination of nanoindentation techniques and numerical and analytical models. Two different alloys, containing different forms of δ -zirconium hydride (blister and rim), were analyzed at room temperature and at elevated temperatures up to 300 ∘ C. A reduction of hardness from RT to 300 ∘ C showed an approximately linear relationship with the change in temperature. For the δ -zirconium hydride rim, the hardness reduced from 3.73GPa at RT to 1.49GPa at 300 ∘ C, a reduction of 61 % . For the δ -zirconium hydride blister, hardness decreased from 3.5GPa at RT to 1.91GPa at 300 ∘ C, a reduction of 45 % . The yield stresses were calculated using two approaches: a numerical model proposed by Johnson to calculate values at RT, and another proposed by Dao for values up to 300 ∘ C. At RT, the yield stress for the δ -zirconium hydride rim obtained was 883 ± 21MPa, 224MPa at 300 ∘ C. The δ -zirconium hydride blister showed a reduction from 879.5 ± 10.5MPa at RT to 324MPa at 300 ∘ C, a reduction in 61 % and 45 % for the hydride rim and blister, respectively. Through this combination of experimental and modeling techniques, this study showed the variation of hardness and yield stress in complex systems, and in different environments, using nanoindentation as the main characterization technique.