Effect of loading condition and stress state on damage evolution of silicon particles in an Al-Si-Mg-Base cast alloy

Abstract

Damage evolution of Si particles in a Sr modified cast A356(T6) Al alloy is quantitatively characterized as a function of strain under tension, compression, and torsion. The fraction of damaged Si particles, their size distributions, and orientation distribution of particle cracks are measured by image analysis and stereological techniques. Silicon particle cracking and debonding are the predominant damage modes. Particle debonding is observed only under externally applied tensile loads, whereas particle cracking is observed under all loading conditions. The relative contributions of Si particle debonding and fracture to the total damage strongly depend on stress state and temperature. For all loading conditions and stress states studied, the average size of damaged Si particles is considerably larger than the bulk average size. The rate of damage accumulation is different for different loading conditions. At a given strain level, Si particle damage is lowest under compression and highest under torsion. The anisotropy of the damage is highly dependent on the deformation path and stress state. Under uniaxial tension, the cracks in the broken Si particles are mostly perpendicular to the loading direction, whereas in the compression test specimens they are parallel to the loading direction. The Si particle cracks in the torsion and notch-tension test specimens do not exhibit preferred orientations. The quantitative microstructural data are used to test damage evolution models.

Analysis of Stress and Strain Fields in and around Inclusions of Various Shapes in a Cylindrical Specimen Loaded in Tension

“…The nucleation process starts with the largest particles and becomes energetically less favourable as the size of the particles decreases [1], [3], [4], [5], [6], [7]. 2.…”

Simulation of mechanical behaviour of cast aluminium components

“…[9][10][11] The plastic behaviour and fracture of cast aluminium alloys is furthermore highly affected by the characteristics [12][13][14] and damage 11,[15][16][17][18] of the Si-particles, where especially ductility 13 and strain hardening rate is increased with increased aspect ratio of the Si-particles. 15,16,19,20 Damage of the Si-particles consists of three stages: cracking or debonding, microcrack formation and growth, and local linkage of microcracks, 6,21 and both cracked 6,11,17,18 and debonded 18,22 particles may initiate global fracture. Particle fracture is caused by incompatibility stresses between particle and matrix, 18,22 and in general larger and longer particles are more likely to crack.…”

“…15,16,19,20 Damage of the Si-particles consists of three stages: cracking or debonding, microcrack formation and growth, and local linkage of microcracks, 6,21 and both cracked 6,11,17,18 and debonded 18,22 particles may initiate global fracture. Particle fracture is caused by incompatibility stresses between particle and matrix, 18,22 and in general larger and longer particles are more likely to crack. 6,17 The probability of particle-cracking, ppc, can be described by Weibull statistics as 11…”

Particle cracking and rotation during plastic deformation of 7075 aluminum alloy

“…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.…”

“…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.…”