Investigation and Nanomechanical Behavior of the Microconstituents of Al-Si-Cu alloy After Solution and Ageing Heat Treatments

Abstract

The effects of heat treatment on the microstructural evolution and mechanical behavior of Al-Si-Cu alloy were investigated. Solution heat treatment was performed at 500^oC/6h and 540^oC/6h, followed by quenching in warm water at 60ºC. Lastly, artificial ageing treatment was performed at 160ºC/6h, 190ºC/4h and 210ºC/2h. The microstructural evolution of the samples before and after heat treatments was analyzed by optical microscopy, scanning electronic microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Analyses revealed the presence Al₅FeSi, Al₁₅(FeMn)₃Si₂, Al₂Cu and Si particles. The morphologies of the present phases were dependent on the heat treatment. Solution treatment at 540ºC/6h resulted in significant softening of the alloy compared with the treated samples at 500ºC/6h. Vickers hardness analysis indicated that the hardness peak of the alloy after heat treatment was about 125 HV. Mechanical properties of different phases have been investigated by nanoindentation technique, which indicated that the highest hardness and modulus of elasticity were found for the Si particle, especially those distributed in the microstructures of the samples submitted to higher solution and ageing temperatures.

Keywords:
Aluminum alloys; Intermetallic compounds; Heat treatments; Nanoindentation