Role of Si particle damage on fatigue characteristics of cast Al–Si alloys

Abstract

In the present study, initiation and evolution of damage at eutectic and primary Si particles during monotonic and cyclic loadings were investigated utilising in situ studies. Al-7%Si and Al-20%Si binary alloys were produced as model materials. Their damage behaviour was analysed in terms of composite theory. In the tensile tests, particles were found to crack perpendicular to a loading axis, being triggered by a far-field uniaxial stress. The damage is accumulated gradually with an increase in applied strain. The in situ strengths of the Si particles are 500-900 MPa for the small eutectic Si particles, whereas it is as low as 200 MPa for the coarse primary Si particles. During the cyclic loading, gradual accumulation of damage at the Si particles was observed with the increase in number of cycles. Propagating through such a weakened zone, a fatigue crack seems to receive some acceleration by the existence of the cracked particles ahead of it. The degree of acceleration was quantitatively evaluated by experiments.

Analysis of fatigue crack initiation and S–N response of model cast aluminium piston alloys

“…They attributed this observation to the fact that larger particles are more likely to contain flaws and re-entrant corners (size effect) and therefore more likely to fail preferentially. Nishido et al [48] have also shown that large primary Si particles require less stress to fracture than small eutectic Si particles. As for particle shape, it is believed that particles with sharp re-entrant angles are likely to induce higher stress concentrations [49].…”

Influence of the microstructure on the machinability of heat-treated Al–10.8% Si cast alloys: Role of copper-rich intermetallics

“…13. It was reported that the strength of Si particles was 500-900 MPa for the fine eutectic Si particles whereas it was as low as 200 MPa for the coarse non-modified Si particles (Nishido et al, 2004). Consequently, the non-modified acicular silicon structure provides an easy path for fracture, resulting in decreases in the cutting force during the machining of the M0 alloy, as shown in Fig.…”

Experimental and numerical investigations of the effects of the spatial distribution of α phase on fracture behavior in hypoeutectic Al–Si alloys

“…Due to the increasingly widespread applications of cast Al-Si alloys in automotive and aircraft industries, a large volume of research has been conducted to investigate the microstructure-property relationships in such alloys [1][2][3][4][5][6][7][8]. In those studies, the Al-Si alloys were generally produced by mould casting coupled with different cooling rates.…”