Investigation of effect of compositional modification of zinc-aluminum alloy ZAMAK-5 on mechanical properties and microstructure

In this study, the effect of additional titanium, manganese and chromium has been investigated that has been separately added at 450 oC or 650 oC without changing orginal composition of base alloy, on the microstructure and mechanical properties of a Zn-Al alloy (% 3,5-4,3 Al, %0,75-1,25 Cu, %0,03-0,08 Mg, % 95< Zn) which is known commercially as ZAMAK5. Specimens that included additional alloying element (% 0,057 and % 0,126 Mn, % 0,035 and % 0,053 Cr, %0,01, % 0,028 and % 0,03 Ti) in weigth percentages were cast into permanent and sand moulds at 450 oC, 600 oC, respectively. Microstructure of the alloys were investigated with optical microscope, scanning electron microscope and EDX. Elemental analyses were conducted with X-ray fluorescence (XRF) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Hardness, compression and three point bending tests were conducted. In the castings made into sand molds, metal temperature was recorded during cooling and cooling curves were determined. Acording to elemental analyses, it was observed that additional alloying elements did not combine with base alloy as much as expected. Microstructure investigations shows that additional alloying elements did not effect size of η and eutectic phases. Intermetallics that includes Cr and Mn were seen in alloys that have Cr and Mn content. Because of longer cooling time, bigger η and eutectic phases were seen in sand cast specimens when they compare to die cast specimens. While hardness results of sand cast specimens were between 80 – 88 HB, results of die cast specimens were between 95 – 105 HB. Except Mn added alloys, all alloys that were produced in this study have higher hardess value than base alloy. Die cast specimens' bending strength values are between 570 – 700 MPa. It was seen that only Ti added alloys' value of bending strenght is higher than base alloys', other alloying elements effect negative on bending strenght. It was determined that although additional alloying elements and their amounts that are used in this study effect hardness of base alloy positively, they cause negative effects on strenght