Effect of Recycling on the Mechanical Properties of 6000 Series Aluminum-Alloy Sheet

Sustainability is one of the biggest values of today and for the future of our society; a responsible usage of material in every sector is fundamental to achieving sustainability goals. Aluminum alloys are some of the most promising materials in terms of strength and weight, but their production implies the emission of a high amount of CO2. For that reason, the study and development of aluminum alloys with increasing scrap content play a central role in future applications. In the current study, two sheet-aluminum 6181 alloys with different scrap content were analyzed and compared with a 6181 alloy coming from primary production. The alloys were compared in terms of chemical composition, microstructure, tensile properties, and forming behaviors. The results showed that the alloys coming from secondary productions contained a higher amount of manganese, iron, and copper. The metallurgical and mechanical behaviors were very similar to those of the primary produced alloy. Nevertheless, a drop in formability was shown in the aluminum alloys containing a high scrap amount when stressed in a biaxial condition. The study demonstrated the viability of 6181 alloy production using a high scrap amount, highlighting the main difference with the same alloy coming from primary route production.

A Simple Procedure for the Post-Necking Stress-Strain Curves of Anisotropic Sheet Metals

Modelling the anisotropic plasticity of a metal requires the derivation of various experimental flow curves from specimens machined along different orientations and, depending on the anisotropy model, tested under different loading modes (tension, compression, torsion). The derivation of stress–strain curves from tensile experiments is a common practice within the uniform straining range but still presents some uncertainties after necking onset. Modern sheet metals, for structural applications where significant energy absorption is required, may exhibit early necking and prolonged post-necking ductility; when such alloys also exhibit pronounced anisotropy, the derivation of their flow curves may be challenging, whatever the loading mode or the specimen direction. This work examines the experimental procedures for determining the true-stress–true-strain curve and the anisotropic strain ratio, extended over the post-necking range and up to failure, from representative tensile tests along the rolling direction of PHS-1800 steel and aluminum 6181 alloy. The validity ranges of different standard procedures for stress–strain derivation are investigated to understand when and how fast the typical true-stress–true-strain data start to depart from the effective material response. Other considerations, based on simple experimental and post-processing procedures, aim at a procedure delivering useful information about the material response over the post-necking range and up to failure. The procedure to retrieve post-necking true curves and anisotropy ratios is then applied to tensile tests at static, intermediate, and high strain rates on the two sheet metals of interest.