Physical Examination of Brass Deposits

Abstract

Abstract Microscopic examination of average brass deposits revealed a fairly uniform deposit of thickness varying from 0.0006 to 0.00004 inch, the brass deposit being thinner at the centre of the plate than at the edges. β-brass was obtained at points where porosity occurred in the base metal. The deposit was collected in aggregates or hillocks dispersed fairly evenly over the plate, a condition which was confirmed by examination under the electron microscope. With this instrument it was demonstrated that bad bonding brass was nonuniform over the surface, a fact further substantiated by subsequent x-ray analysis. Differences in crystallite size and in degree of crystalline orientation appeared to have no consistent effect on the bonding properties of the brass. The brass deposit showed, however, a high degree of preferred orientation, as is usual with electrodeposits. As regards the preparation of the base metal, the use of too much oil and too high a speed of machining appeared to have a detrimental effect. This appeared to be due to the fact that a nonuniform state of strain was produced over the surface as samples of mild steel of various degrees of strain, but uniform over the surface, gave consistently good adhesion.