Stress asymmetry of stoichiometric NiAl single crystals

The yield stress properties of stoichiometric NiAl single crystals were investigated in terms of crystal orientation, temperature and the deformation mode. The calculated critical resolved shear stress (CRSS) was a strong function of crystal orientation, temperature and the deformation mode whether tension or compression. The CRSS was, in a wide range of experimental conditions, higher in the sequence of {110}〈100〉, {100}〈100〉 and {hk0}〈100〉 slips. The CRSS in compression was higher particularly at low temperatures than the CRSS in tension. The tension-compression asymmetry on the CRSS was understood qualitativelys being due to the effect of the normal stress on the core structure of a 〈001〉 dislocation and a 〈111〉 dislocation. It was suggested that a compressive normal stress makes the core configuration more sessile, resulting in the increased stress effectively at low temperatures.