Edge cracking in automotive components

A new version of AA 5754 alloy was produced at Aludium with purer chemical composition and a special manufacturing process to improve the Edge-cracking resistance. The main hardening element, magnesium, was kept at the same level in both alloys, but the amount of iron and silicon, was reduced.

During this case study, the new alloy was tested and compared with the standard AA5754 H111 in Aludium facilities to determine the chemical composition, microstructure, mechanical properties and FLD. FormPlanet used an in-house optimised and patented methodology, based on the Essential Work of Fracture (EWF), to evaluate the fracture toughness as the most suitable fracture parameter to predict edge cracking in high-strength metal sheets.

Conclusions based on the Essential Work of Fracture testing results, indicate that the new material develop by Aludium shows higher fracture toughness and plastic work and that more energy is needed to propagate the crack after initiation.

Fracture toughness evaluation of thin metal sheets (1-3 mm of thickness), using mechanically notched or fatigue pre-cracked DENT specimens, and thick sheets (>3mm of thickness) by bending tests of fatigue pre-cracked SENB specimens, following fast and affordable methodologies based on the Essential Work of Fracture (EWF). The EWF is the most suitable fracture parameter to rationalise crack-related problems in high-strength metal sheets, such as edge fracture or crash behaviour.