Mechanical Properties of Thermomechanical Treated Hyper-Eutectic Al–Si–(Fe,Mn,Cu) Materials

Tensile and high-cycle fatigue behavior of thermomechanical treated hyper-eutectic Al–Si–(Fe,Mn,Cu) materials were studied. Through the repeated thermomechanical treatment (RTMT) which is a repeat of the multi steps cold-working followed by heat treatment, Si crystals and/ or intermetallic compounds were broken into some fragments and dispersed in the aluminum matrix. Fine dispersion of the second phase particles exhibited good ductility, since early fracture was overcome. A few large Si crystals or aggregates of compounds, however, gave an origin of fatigue crack generation. Since microcrack linkage generates a larger fetal crack, not only refinement but also random distribution of second particles may be required to improve fatigue strength at and below room temperature. At higher temperature, on the other hand, dynamic recovery may cause apparent strain rate dependence on flow curves