The Development of Aluminum Alloy Piston for Two-Stroke Cycle Engine by Powder Forging

Abstract

The purpose of this paper is to investigate the influences on mechanical properties of two-stroke cycle motor pistons manufactured by casting, conventional forging and powder forging, through the comparison of characteristics, merits and disadvantages of each forming technology. For each forming technology, the optimal process parameters were determined through the experiments for several conditions, and microstructure, hardness, tensile strength and elongation of pistons are compared and analyzed. In conventional forging process, material temperature was <TEX>$460^{\circ}C$</TEX> and the die temperature was <TEX>$210^{\circ}C$</TEX> for the Al 4032. The optimal condition was found as solution treatment under <TEX>$520^{\circ}C$</TEX> for 5 hours, quenching with <TEX>$23^{\circ}C$</TEX> water, and aging under <TEX>$190^{\circ}C$</TEX> for 5 hours. In powder forging process, the proper composition of material was determined and optimal sintering conditions were examined. From the experiment, 1.5% of Si contents on the total weight, <TEX>$580^{\circ}C$</TEX> of sintering temperature, and 25 minutes of sintering time were determined as the optimal process condition. For the optimal condition, the pistons had 76.4~78.3 [HRB] of hardness, and 500 [MPa] of tensile strength after T6 heat treatment.