On the determination of the crystal-axes in "single-crystal" aluminium bars by means of X-rays

Mr. G. I. Taylor, F. R. S., and Miss C. F. Elam investigated recently the distortion of "single-crystal" aluminium bars during a tensile test. By purely geometrical measurements they found that certain planes exist in the test-piece which, during its extension, remain undistorted. That is to say, that any curve drawn on these planes keeps its shape. From these observations they concluded that the test-piece must have a lattice-structure extending through the bulk of the material, or, in other words, that these test-pieces are single crystals. Mr. Taylor asked the writer to investigate by means of X-rays whether the "undistorted" or slip-planes could be related with the crystal-planes of the material which is known to crystallize in a face-centered cubic lattice. The result of this investigation is given in the above-mentioned paper of Taylor and Elam. The present paper is meant to give an account of the experiments so far as the X-ray work is concerned. A few points will be discussed later on which are likely to be of a more general interest.