Of Si, And Bi, Sb Za40 Alloy And Performance Impact

Zn-Al alloy has a good anti-friction and wear-resistance material, mainly being in place of copper alloy to product shafting bearing and bearing bushing with a good economic return in Machinery Industry. It has been becoming important research content to improve hard particles phase in the number and types in the Zn-Al alloy to a larger range of alternatives to copper alloy because of ZA27 alloy with a small number of hard partices and low hardness. The high Al-zinc alloy(Al≥27%)with Si has good mechanical properties and far greater wear-resistance than ZA27, but plenty of blocky primary Si give rise to alloy combination properties reduction with increasing silicon content and Alloy's "aging" become more serious with the increase of the Al content in the alloy. In this paper, Si/Al concept was put forward firstly in order to control the Si content of high Al-zinc alloy and the morphology of primary silicon has been perfect effectively by Bi and Sb elements added into ZA40 alloy and a new modification treatment adopted, so The mechanical properties of alloy and dimensional stability was improved. These are significant innovation in the casting industry.In this dissertation, the effects of Si, Bi and Sb additions on the microstructure and combination property of ZA40 alloy are systematically studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), microhardness, tensile test, impact toughness etc. The main research work and conclusions are presented as follows:1,Polygonous primary Si appeared in the ZA40 alloy structure when the Si/Al≥9%(Si 3.6wt%) . The number of primary Si increased and the shape of primary Si worsened with increasing Si/Al. Comprehensive consideration, the combination mechanical properties are optimum with Si/Al up to 9%, the Tensile strength 390MPa, Hardness 151HB, Extensibility 1.0%, Impact flexibility 5.76J /cm-2. The wearing capacity of Si /Al 9% ZA40 alloy is minimum 0.0033g, only 10.8% of standard ZA27 alloy. The dimension change ratio of ZA40 alloy decreased with increasing Si/Al.2,When Bi was added into the Si/Al≥15% ZA40 alloy, the microstructure of alloy consisted ofαphase ,primary Si ,εphase, pure Bi phase and eutectoid (α+η) by XRD detection. When 1.0% Bi is added, primary Si was evidently refined and combination properties of ZA40 alloy are optimum, the Hardness 134HB, Impact flexibility 4.15J /cm^-2, increased 15.6% than no adding Bi alloy. When 0.5% Bi added, the wearing capacity of ZA40 is 13.8% of standard ZA27 alloy and 33.6% of no added Bi ZA40 alloy as result of Bi self-lubricating action.3,Bi element is a significant influence factor on dimension change ratio at room temperature. Dimension change ratio of alloy is the smallest with adding 1.0% Bi, only 0.0843‰, decreasing 79.3% than no adding Bi alloy. The effects of all test factors―Bi element, Si/Al and their interaction, are insignificant on dimension change ratio at 150℃. By contrast, Si/Al is the main factor that affect dimension change ratio at 150℃.4,When Sb was added into the ZA40 alloy with Si, the microstructure of alloy consisted ofαphase ,primary Si ,εphase, Zn₄Sb₃ compound phase and eutectoid (α+η) by XRD detection. Sb and Zn form Zn₄Sb₃ compound that can refineαphase as a result of inhibiting growth ofαarborescent structure. When 1.8% Sb is added, primary Si was evidently refined and combination properties of ZA40 alloy are optimum, the Hardness 153HB, Impact flexibility 3.70J /cm^-2, increased 3.1% than no adding Bi alloy. When 0.5% Sb added, the wearing capacity of ZA40 is 26% of standard ZA27alloy and 63.2% of no added Sb ZA40 alloy.5,Sb element is a significant influence factor on dimension change ratio at room temperature. Dimension change ratio of alloy is the smallest with adding 1.0% Sb, only 0.0090‰, decreasing 97.7% than no adding Sb alloy. The effect of all test factors―Sb element, Si/Al and their interaction, is insignificant on dimension change ratio at 150℃. By contrast, Sb element is the main factor that affect dimension change ratio at 150℃.