An innovative solution for the automotive industry is to replace the copper used for wiring harnesses with aluminum alloys, such as the aluminum-magnesium-silicon 6101 alloy. Wiring harnesses are composed of thin strand arms obtained by a wire drawing process. These strands are susceptible to exposure to a corrosive environment and fatigue solicitations simultaneously. The fatigue endurance of this alloy was studied using the stress-life approach for three metallurgical states representative of three colddrawing steps. Fatigue tests performed in corrosive media tests highlighted a strong decrease of the 6101 alloy lifetime due to fatigue-corrosion interactions and a modification of failure modes.

An Al-Mg-Si aluminium alloy was shaped by using a two-pass equal-channel angular pressing (ECAP) process. This led to fragmentation of the coarse Fe-rich intermetallics (IMCs), a decrease in grain size and an increase in the high angle grain boundary (HAGB) density, with overconcentration of HAGBs around the IMCs. Corrosion tests in NaCl solution showed that, before and after ECAP, only pitting corrosion occurred. However, for ECAP samples, pits were more numerous due to the fragmentation of the IMCs; they were also larger and less deep, their propagation being strongly influenced by the presence of very small grains around the IMCs.

International audienceMicrostructural states produced by each step of the manufacturing process leading to the production of automotive strand arms in 6101 aluminum alloy (AA6101) for wiring harnesses were investigated in relation to their corrosion behavior in NaCl solution. The observed corrosion morphology,i.e., pitting corrosion or intergranular corrosion, was strongly dependent on the precipitation state, i.e., mainly the presence of intergranular Mg2Si precipitates. A ‘grain size – corrosion resistance’ relationship was also evidenced with an ennoblement of the corrosion potential for wires heavily cold drawn, which were characterized by a nanometric grain size. Dislocation density as well as the homogeneity of alloying element distribution were also found to be relevant parameters for explaining the electrochemical behavior of each microstructural state. Plastic deformation and recrystallization phenomena occurring during the manufacturing process were found to be associated with redistribution of alloying elements, which impeded the formation of intergranular Mg2Si precipitates. Therefore, in the present study, the cold drawing process was found to increase the intergranular corrosion resistance of AA6101

The influence of equal channel angular pressing ( ECAP) on the corrosion fatigue behaviour of an Al-Mg-Si alloy was studied. Preliminary fatigue tests in air showed an increase in fatigue lifetime for ECAP samples, as com pared to as-received samples, related to the ECAP-induced grain refinement. After pre-corrosion, the fatigue lifetime was lower for ECAP samples than for as-received samples, because the fragmentation of coarse inter metallics during ECAP led to an increase in the density of corrosion defects. Corrosion fatigue tests demonstrated a synergy between cyclic mechanical loading and corrosion processes for all samples; a deleterious effect of ECAP was also noted.

The effect of cold-working, i.e. cold drawing, and aging treatment on the corrosion behavior of a 6101 aluminum alloy was investigated in NaCl solutions. The 6101 T4 aluminum alloy was found to be susceptible to only pitting corrosion with filaments growing from the pits and propagating into the matrix. A 185°C-10 hours aging treatment led to a shift of the corrosion potential of the 6101 alloy towards more cathodic values and promoted intergranular corrosion. When the 6101 alloy was both cold-drawn and aged, modification of the corrosion potential was still observed and intergranular corrosion was not observed for the cold-drawn samples.