Abstract
This study was conducted with the intention of investigating a new experimental alloy, namely the 396 alloy which belongs to the Al-Si near-eutectic cast alloy group and contains about 11%Si. In the light of the above, the main purpose of the work is to report on the changes observed in the mechanical and/or machinability criteria resulting from the effects of the presence of two levels of Cu, namely 2.25% and 3.5%; and of the effects of two levels of Mg, namely 0.3 and 0.6%. In addition to the preceding, the effects of Mg-free alloys and Sr-modification on these same alloys were also investigated.
The results demonstrate that the increase in the levels of Cu and/or Mg in the 396-T6 alloy has a detrimental effect on drill life. Such an effect may be attributed to the formation of large amounts of the coarse blocklike Al2Cu phase, together with the formation of thick plates of the Al-Si-Cu-Mg phase. The Mg-free experimental alloy displays the lowest cutting force and moment in addition to producing the highest number of holes in the alloys studied. A comparison of the non-modified alloy and the Sr-modified alloy (containing the same level of Mg and Cu additions) in terms of the number of holes drilled, reveals that the morphology of Si particles has a noticeable effect in governing the tool life of near-eutectic Al-Si alloys.