Micromechanisms of short fatigue crack growth in an Al–Si piston alloy

Abstract

The short fatigue crack growth behaviour of a model cast aluminium piston alloy has been investigated. This has been achieved using a combination of fatigue crack replication methods at various intervals during fatigue testing and post-mortem analysis of the crack profiles. Crack-microstructure interactions have been clearly delineated using a combination of optical microscopy and scanning electron microscopy. Results show that intermetallic particles and eutectic Al-Si regions play a significant role in determining the crack path and growth rate of short fatigue cracks. It is observed that the growth of short cracks is often retarded or even arrested at intermetallic particles and Al-Si eutectic regions. Crack deflection at intermetallics and eutectic Si is also frequently observed. These results have been compared with the long crack growth behaviour of the alloy.

Effect of intermetallic particles and grain boundaries on short fatigue crack growth behaviour in a cast Al–4Cu–3Ni–0.7Si piston alloy

“…Moreover, another key observation not reported previously for this alloy is that cracks preferentially propagate through the intermetallic/Al interfaces whenever they encounter such particles. This was also observed to occur in the hipped version of the 6.9 wt% Si alloy shown in Table . Although propagation through fractured particles is also observed, this is less frequent and mostly confined to thin favourably oriented particles (parallel to the loading direction).…”

“…To the authors' knowledge, there is no report in the open literature that delineates the effect of gbs on the short crack growth behavior of these more complex multi‐component piston alloys. The fatigue crack initiation behaviour of the hipped Al0.7Si and Sr‐modified Al7Si alloys is presented in Mbuya et al Moreover, details of the short crack growth behaviour of the hipped Sr‐modified Al7Si alloy are reported elsewhere …”

Influences of strain rate on the low cycle fatigue behavior of gravity casting Al alloys

“…Mbuya and P.A.S. Reed [14]. Specifically, it appears that most of slip lines are located close to one pore (see Fig.…”

Application of FEM Analysis for Evaluation of the Stress and Deformation Distributions in the Top Layer of A390.0 Alloy During Friction

“…Moreover, the distribution of the individual eutectics and the primary silicon crystals has a significant influence on the fatigue strength of silumins, e.g. by exposition of microcracks after the silicon crystal boundary [9].…”