Quantitative characterization of three-dimensional damage evolution in a wrought Al-alloy under tension and compression

Three-dimensional (3-D) microstructural damage due to cracking of Fe-rich intermetallic particles is quantitatively characterized as a function of strain under compression and tension in an Al-Mg-Si base wrought alloy. The 3-D number fraction of damaged (cracked) particles, their average volume, average surface area, and shape factor are estimated at different strain levels for deformation under uniaxial tension and compression. It is, shown that, depending on the type of loading, loading direction, particle shape, and microstructural anisotropy, the two-dimensional (2-D) number fraction of, the damaged particles can be smaller or larger than the corresponding true 3-D number fraction. Under untaxial tension, the average, volume and surface, Area of cracked particles decrease with the strain. However, the average volume and surface area of the cracked particles increase with the increase in the compressive strain, implying that more and more larger elongated particles crack at higher and higher stress levels, which is contrary to the predictions of the existing particle cracking theories. In this alloy, the damage development due to particle cracking is intimately coupled with the particle rotations. The differences in the damage evolution under tension and compression are explained on the basis of the differences in the particle rotation tendencies under these two loading conditions.