EFFECT OF SURFACE FINISH AND SHEET THICKNESS ON ISOSTATIC DIFFUSION BONDING OF SUPERPLASTIC TI-6AL-4V

The aim of the present work was to determine the process conditions of pressure, temperature, and time required to produce high quality isos tatic diffusion bonds in Ti-6Al-4V for two surface finishes. In additi on, the conditions to produce a sound bond between two sheets or plate s of Ti-6Al-4V having different thicknesses were investigated. An asse ssment of the quality of bonds produced was made on the basis of metal lographic examination, lap shear strength measurements, and SEM examin ation of the shear fracture surfaces. Sound bonds were produced in the as received and pickled 1.6 mm thick sheet in under 1 h with an appli ed pressure of 2.1 MPa at both 940 and 920 degrees C and for the P60 g round surface finish at 940 degrees C, but the time increased to 1.5 h at 920 degrees C for the coarser surface finish. Variations in sheet thickness from 1.6 to 10 mm were found to have no effect on the bondin g time. These results were compared with the predictions of a model of isostatic diffusion bonding. (C) 1997 The Institute of Materials.