Improvement of Paint Hardening Response of a Novel Al-Mg-Si Alloy for Automotive Panel by Adding Zn and Pre-Ageing Matching

Abstract

In the present work, the microstructure and properties of a novel Al-0.90Mg-0.78Si alloy with Zn addition were investigated by electron back scattering diffraction (EBSD), high transmission electron microscopy (HREM), mechanical properties and Erichsen tests. The average grain size of the alloy after pre-ageing was about 20 μm. The yield strength and elongation of pre-aged alloy was 137 MPa and 30% respectively. The IE value of the alloy was 8.6 mm. After paint baking at 170 °C for 30 min, the increment of yield strength was about 100 MPa. GP(II) zones were formed in the alloy during paint baking process through adding Zn, which should play a very important role for improving paint hardening response. GP(II) zones and η ́ phases were formed after artificial ageing at 170 °C for 10 h.