Revealing the grain structure of metals by ultrasonics

There is a need for a non-destructive system to test the structural quality of polycrystalline materials, especially metals. An ultrasonic technique is one means of doing this and a method is proposed which is conventionally divided into three distinct stages. A system has been developed to carry out the first of these, this being the examination of the general topography of a test piece in terms of the spatial variation in grain structure. Results obtained with the system on a differently heat-treated steel bar, an aluminium bar previously subjected to shear stress producing a remanent deformation, and on samples of Armco and high-purity irons are given. These are then discussed. Finally, the lines along which the present research is proceeding are briefly described.