Precipitate-mediated enhancement of mechanical and electrical properties in HPTE-processed Al–Mg–Si alloy

Abstract

In this study the effect of high-pressure torsion extrusion (HPTE) and artificial aging (AA) on the strength and electrical conductivity of an Al–Mg–Si alloy was investigated. The resulting material shows remarkable improvement in ultimate strength reaching 380 MPa and in electrical conductivity with 53 % IACS (International Annealed Copper Standard), after post-processing aging at 160 °C for 10 h. X-ray diffraction analysis and electron backscatter diffraction were employed to analyze the structure of the alloy caused HPTE followed by AA. Transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) spectroscopy were used to study the morphology, elemental composition, and crystal structure of the secondary phases. The study confirms that Guinier-Preston (GP) zones and nano-scale precipitates created during the deformation and subsequent heat treatment are evenly distributed inside the grains. Chemical composition analysis of the precipitates indicated the presence of one main phase based on the Mg/Si ratio coexisting with a low volume fraction of other phases in this Al grade. High-resolution TEM revealed precipitates either with a partially ordered structure or a fully crystalline structure. Strength and electrical conductivity modeling were carried out based on the microstructural characterization results. The findings of this study indicate that HPTE together with thermal treatment has the potential as new approach for processing of commercially significant aluminum alloys.