Deformation behaviour of pearlite in the copper-aluminium system

Abstract

The room temperature mechanical properties of eutectoidal binary aluminium bronze (Cu + 11.8 wt % Al) have been studied as a function of interlamellar spacing in the pearlite. Specimens with different lamellar spacings were produced by isothermal transformations at various sub-critical temperatures. The proportional limit, 0.2% yield strength and fracture strength were found to be inversely related to the square root of the lamellar spacing. This is in accordance with the mechanism suggested by Ansell and Lenel for deformation of two-phase alloys, according to which the criterion for macroscopic yielding is the fracture of the non-deformable phase, caused by the stress-concentration due to pile-up of dislocations at the lamellar interfaces. Metallographic evidence supporting the suggested mechanism is also presented.