Three-dimensional particle cracking damage development in an Al–Mg-base wrought alloy

Abstract

Experiments have been performed to quantitatively characterize the three-dimensional (3-D) microstructural damage due to cracking of Fe-rich intermetallic particles in an Al Á/Mg-base extruded 5086(O) alloy as a function of strain under uniaxial compression and tension. The 3-D number density and average volume of the cracked particles are estimated using the unbiased and efficient large area disector (LAD) stereological technique. In each specimen, the two-dimensional (2-D) number fraction of cracked particles is significantly lower than the corresponding 3-D number fraction. Therefore, the conventional 2-D damage measurements considerably underestimate the true 3-D damage due to particle cracking in this alloy. Comparison of the 3-D damage data on the 5086(O) alloy and earlier data on 6061(T6) alloy reveals that at all tensile/compressive stress levels higher than the yield stress of both alloys, the 3-D number fraction of cracked Fe-rich intermetallic particles in the 5086(O) alloy is significantly lower than its corresponding value in the 6061(T6) alloy. Therefore, the 5086(O) alloy is less prone to damage progression due to particle cracking compared to the 6061(T6) alloy. In both the alloys, significant rotations of the Fe-rich intermetallic particles occur during deformation under uniaxial compression. These rotations tend to align the particles along the direction of induced tensile stretch. The particle rotations in turn affect the progression of damage due to particle cracking. For deformation under uniaxial compression, the average volume of cracked Fe-rich particles increases with the increase in the strain. These observations are explained on the basis of the particle rotations. #

Particle cracking and rotation during plastic deformation of 7075 aluminum alloy

“…It must be mentioned that most of the damage evolution models implicitly assume that the particles remain stationary when the solid matrix is plastically deformed under an applied load and, therefore, the particle orientations do not change with the plastic strain. It has been reported that significant rotations of Fe-rich constituent particles occurred during the deformation of the ductile matrix of the Al-alloys [9,17]. The particle rotations have also been observed in some samples of this study, in particular in the torsion samples.…”

“…The particles rotations in tension were very similar to that in the unstrained specimen since the tensile loading direction was parallel to the rolling direction and, therefore, significant particle rotations did not occur during uniaxial tensile deformation. Clearly, under the uniaxial compression along the rolling direction, the Fe-rich particles rotated and tended to align themselves along a direction that was perpendicular to the loading direction, which was the direction of induced tensile stress [9,17]. The extent of particle rotations in this study, however, appeared to be significantly less in the small strain levels.…”

“…Ductile fracture of many technologically important materials involves cracking the intermetallic inclusions/particles, the growth of voids at the cracked particles, and void coalescence [1][2][3][4][5][6][7][8][9][10]. Such damage evolution processes are associated with deformation and fracture of ferrous as well as nonferrous alloys.…”

“…Such damage evolution processes are associated with deformation and fracture of ferrous as well as nonferrous alloys. The 5xxxx, 6xxx, and 7xxx series commercial wrought Al-alloys usually contain brittle Fe-rich coarse constituent particles that crack during the plastic deformation of these alloys, giving rise to microstructural damage nucleation [8][9][10]. Therefore, it is of interest to quantitatively characterize the cracking of such brittle constituent particles as a function of strain under different loading conditions.…”

“…There have been numerous investigations on the characterization of particle cracking damage in wrought and cast Al-alloys [4,[6][7][8][9][10]. Nonetheless, all earlier investigations involved manual detection of cracked particles, which is very laborious and time consuming.…”