The distortion of crystals of aluminium under compression. Part II.―Distortion by double slipping and changes in orientation of crystals axes during compression

Abstract

Changes in the orientation of crystal axes during compression of a disc cut from a single crystal of aluminium are discussed. They are in accordance with the prediction made on assumption that the crystal slips as determined by distortion measurements. As in case of tensile test pieces, crystal axes always take a position where two possible planes of slip are symmetrically disposed in relation to the stress, but in this case, the orientation of crystal axes relative to normal to flat surfaces of specimen is quite different from their orientation relative to axis of tensile test piece. After the axes have taken the symmetrical position, Laue photographs show that they remain there, even when distortion is very great. Tests were continued till thickness of specimen was only 0.28 its original thickness. Distortion during period when crystal axes remain in symmetrical position is due to slipping on two symmetrically disposed planes of slip. The bearing of the results on structure of rolled metals is discussed and distortions of cubical blocks of material, due to various types of double slipping, are compared, to find out which is most likely to occur.