Microhardness variation and related microstructure in Al–Cu alloys prepared by HF induction melting and RF sputtering

LM2S, Physics department, Faculty of Science, Badji-Mokhtar-Annaba University, 23200 Annaba, Algeria

Corresponding author: mydebili@yahoo.fr

Received: 9 April 2008
Revised: 18 December 2008
Accepted: 14 January 2009
Published online: 17 February 2009

Abstract

The materials under consideration are binary aluminium-copper alloys (10 at% to 90.3 at%Cu) produced by HF melting and RF magnetron sputtering. The resulting micro structures have been observed by standard metallographic techniques, X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Vickers microhardness of bulk Al–Cu alloys reaches a maximum of 1800 MPa at 70.16 at%Cu. An unexpected metastable phase has been observed within aluminium grain in Al-37 at%Cu. The mechanical properties of a family of homogeneous AlCu_x (0 < x < 0.92) thin films made by radiofrequency (13.56 MHz) cathodic magnetron sputtering from composite Al–Cu targets have been investigated. The as-deposited microstructures for all film compositions consisted of a mixture of the two expected face-centred-cubic (fcc) Al solid solution and tetragonal θ (Al₂Cu) phases. The microhardness regularly increases and the grain size decreases both with copper concentration. This phenomenon of significant mechanical strengthening of aluminium by means of copper is essentially due to a combination between solid solution effects and grain size refinement. This paper reports some structural features of different Al–Cu alloys prepared by HF melting and RF magnetron on glass substrate sputtering.