HIGH-TEMPERATURE DEFORMATION OF CUBIC OXIDES

J. L. Routbort
1981 Le Journal de Physique Colloques  
Les courbes contrainte-déformation de MgO et NiO ont un tauxd'écrouissage 8 qui décroît linéairement quand la contrainte augmente jusqu'à un état stationnaire (6=0) alors que la courbe pour CoO présente un crochet de traction et un taux d'écrouissage négatif qui augmente jusqu'à s'annuler quand l'état stationnaire est atteint. Ces résultats prédisent des formes de courbes de fluage similaires pour NiO et MgO, différentes de celle obtenue pour CoO. Finalement, la contrainte T de l'état
more » ... re divisée par le module de cisaillement est très semblable pour les trois oxydes, NiO présentant la plus grande valeur. La dépendance en température de T est donnée pour les trois oxydes par la loi : log T = B -T/A, où A et B sont des constantes. Abstract.-The stress-strain curves for MgO and NiO have a work-hardening rate 6 that decreases linearly with increasing stress to a steady state (8=0) while the curve for CoO has an upper yield point and a work-hardening rate that is negative but increases to zero when steady state is achieved. These results predict that the shapes of the creep curves for NiO and MgO are similar, and different from those obtained for CoO. Finally, the steady-state stress T divided by the shear modulus is very similar for all three oxides, with NiO having the largest value. The functional dependence of T g on temperature T for all three oxides is given by log T = B -T/A, where B and A are constants. 1. Introduction.-High-temperature stress versus strain measurements yield information on the mechanisms of work hardening and recovery. In addition, if the measurements are performed to sufficiently large strains, the competition between hardening and recovery balances and the work-hardening rate becomes zero. At this point the steady-state stress T , which is developed under conditions of nearly constant strain rate (constant crosshead velocity), corresponds to the stress that must be applied to generate the same strain rate in a creep test. The resolved.shear stress versus total shear strain (x vs. y) measurement provides additional information on the behavior of the work-hardening rate and possibly on the mechanisms of hardening and recovery.
doi:10.1051/jphyscol:1981306 fatcat:hh6dn4rvrrbjvgg35ggnn726o4