Plastic Deformation of Calcium Tungstate Single Crystals

摘要

Calcium tungstate deforms by slip on the (001) system above 400C. Simple shear over this plane is the only deformation mode observed under compression at temperatures up to 900C and a strain rate of 0.0010 sec(-1). The critical resolved shear stress is strongly temperature dependent. Crystals cannot be plastically deformed at room temperature, at 400C they are still quite brittle but by 900C they are soft (yield stress, 500 psi) and plastic. Slip traces at all temperatures are fine and straight but those produced at lower temperatures (600-700C) have a greater surface tilt and are more sharply defined than those produced above 800C. This is due to fewer dislocation sources and restrictions on dislocation multiplication at lower temperatures. The role of bonding and crystal structure in the selection of slip parameters is discussed. It is considered that the stacking of the oxygen ions is the dominant factor dictating the slip plane and slip direction. (Author)