The influence of Strontium addition on wear properties of Al–20 wt% Si alloys under dry reciprocating sliding condition

The modification response of Al–20 wt% Si alloys was studied with different Sr addition levels. The wear properties of Al–Si alloys modified by Sr were investigated by using a UMT-3 reciprocating wear machine over a range of normal loads, i.e., 2, 5, 8 N, at the frequency of 50 Hz. The worn morphologies of the wear surface were examined by scanning electron microscopy (SEM). The results show that the primary Si and the interdendritic eutectic matrix are obviously changed after the Sr modification. The frictional coefficient greatly changes at a low load and mains unnoticeably at a high load. In addition, the frictional coefficients of the unmodified alloys decrease with increasing of the load, but those of the modified alloys increase when Sr addition level exceeds 0.04 wt%. The wear volumes of Al–Si alloys are inversely proportional to the hardness. The wear behaviors are optimal in the range of 0.04–0.06 wt% Sr. Adhesive wear is the main mechanism for the unmodified alloys, whereas abrasion wear characterizes in the modified alloys.