Development of aluminum powder metallurgy composites for cylinder liners

摘要

There are several all-aluminum cylinder blocks. A typical example is a mono-block cylinder of alusil alloy produced by low pressure die casting. This material's resistance to abrasion and seizure, however, is not satisfactory for motorcycle; in addition, long processing time is another disadvantage. To cope with these problems, the authors developed a light and highly productive all-aluminum cylinder block with a cast-in liner through die casting. The liner is made from powder metallurgy composite (PMC) with 3 to 5% alumina and 0.5 to 3% of graphite additives. The PMC reconciles abrasion resistance and machinability. The hardness deterioration of the composite due to the heat at die casting is avoided by using heat-resistant rapidly-solidified powders, made from an aluminum-silicon iron alloy, for the matrix. By employing the sliding test and the firing test, PMC showed similar abrasion resistance to grey iron and similar seizure resistance to iron plating under the boundary lubricated condition. Furthermore, the machinability is improved by the use of fine spherical alumina particles of average diameter of 3μm.