X-RAY STUDIES ON THE ANNEALING AND DIFFUSION IN ALUMINIUM ALLOYS.

Abstract

Problems relating to the annealing of cast Al-alloys and diffusoin in super-duralclad plate were studied by X-ray focussing method using Cu Ka radiation. When chill cast Al -alloy containing 4% Cu is gradually heated, the lattice constant becomes large at first and then small, and finally reaches a constant value at about 500°C. These changes correspond to the changes appeared in the dilatometric curve. The time required to obtain, as the value of the lattice constant, by heating at 500°C the mean of initial and final values about 0·4hrs. These values become large by the addition of Mg: such as 0·5, 1·1 and 1·9hrs for 0·5, 1·0 and 1·5% Mg respectively.
The inner part of the super-duralclad plate becomes uniform when annealed several hours at 500°C, but the surface layer does not become uniform and the values of its lattice constant are quite irregular even after being heated for 50hrs. Also, broadening of (511) line of the surface layer begins at about 10hrs and reaches the final value at about 20hrs. Above results show that the diffusion does not take place uniformly and, in the surface layer, non-uniformness becomes noticable by annealing.