M.Sc Tezi Görüntüleme

      In this study, one ternary zinc-aluminium-copper and eight quaternary zinc-aluminium-copper-silicon alloys were produced by permanent mould casting. The friction and wear properties of these alloys were investigated in both as-cast and heat treated (stabilized) conditions using a block-on-disc machine. The results obtained from these investigations were explained in terms of microstructure and mechanical properties of the alloys and compared with those obtained from the SAE 660 bronze under the same test conditions.

      The microstructure of the ternary Zn-40Al-2Cu alloy was consisted of aluminium-rich α, zinc-rich η and copper-rich ε phases and the quaternary Zn-40Al-2Cu-(1-5)Si alloys had a silicon phase in addition to the phases observed in the ternary alloy. The silicon particles showed a homogeneous distribution in the alloys containing up to 2.5%Si, however when the silicon content exceeded this level the silicon particles gave rise to microsegregation by gathering in some areas of the microstructure as separate groups. It was observed that the stabilization treatment had no significant effect on the microstructure of the alloys, but produced fine transformation products in the interdendritic regions.

      The hardness and tensile strength of the Zn-Al-Cu-Si alloys increased with increasing silicon content up to 2,5%Si, above which they decreased as the silicon content increased. It was found that the coefficient of friction decreased with increasing silicon content up to 1%Si, however above this level it increased as the silicon content increased. It was also found that the volume loss due to wear of the alloys decreased with increasing silicon content up to 2,5%, above which it increased as the silicon content increased. In addition the hardness, tensile strength and wear resistance of alloys were found to be reduced by the stabilization treatment applied.

      As a result of these observations it was concluded that the Zn-40Al-2Cu-(1-5)Si alloys have much superior tribological properties compared to the SAE 660 bronze in both as-cast and heat-treated conditions.

      Key Words : Monotectoid Based Zn-Al-Cu-Si Alloys, Silicon Content, Stabilization, Mechanical Properties, Friction, Wear and Tribology