Investigations Of Microstructure And Mechanical Properties Of ZznAl4y Znic Alloy

Low aluminium ZA alloys with excellent properties is widely used in machineryindustry. The alloys, especially alloy No.3zinc alloy, provide the best combination ofstrength, castability, ease of finishing and economical efficiency. Shortcomings suchas inferior properties and dimensional changes occurring at elevated temperatureslimit the use of alloy No.3. In order to improve the quality of the alloy No.3, andmake the products meet the needs of industrial markets better, the elementary andapplied researches have been carried out based on the studies on ZZnAl4Y alloy bothat home and abroad.In order to resolve the problem in data query on thermodynamics and phasediagrams of zinc-base alloys, a thermodynamics and phase diagram database systemhas been developed using Visual Basic6.0software, which is based on the collectionof relevant thermodynamics and phase diagram data of zinc-base alloys. The databasesystem can be used to improve the query efficiency and to design and develop newzinc-base alloys.Equilibrating alloy method, scanning electron microscopy coupled with energydispersive X-ray spectroscopy and X-ray diffraction were used to determine the370°C isothermal section of the Zn-rich corner of the Zn-Al-Ti ternary system, andfound out the effect of homogenization treatment on the microstructure ofZn-4wt.%Al-0.5wt.%Ti (Zn-4Al-0.5Ti) alloy. Based on ZZnAl4Y alloy produced inChina, the reverse modification of Al-5wt.%Ti-1wt.%B (Al-5Ti-B) master alloy onthe structural characteristics and mechanical properties of the alloy is investigated.Microstructure characterization of ZZnAl4Y alloy was carried out using SEM with anenergy dispersive X-ray and XRD. The tensile strength, hardness and impact ductilityof the alloy were conducted using universal tensile testing machine, brinell hardnesstesting machine and impact testing machine, respectively. And the effect ofmodification on the microstructure and mechanical properties of ZZnAl4Y alloy wasinterpreted. Furthermore, one suitable modificator for ZZnAl4Y alloy has beendeveloped, and some attentions have been paid to study the modification efficiencyand modification mechanism.Following conclusions have been obtained:(1) A thermodynamics and phase diagram database system of zinc-base alloys has been developed using Visual Basic6.0software.(2) T+TiZn16+TiZn8, T+TiZn16+η-Zn, T+TiZn+TiZn8, TiZn+TiZn3+TiZn8, T+η-Zn+(α-Al), T+(α-Al)+TiAl3and T+TiAl3+TiAl2seven three-phaseregions exist at the370°C isothermal section of the Zn-rich corner of the Zn-Al-Titernary system.(3) T phase does not exist in as cast Zn-4Al-0.5Ti alloy, but the T phase occurs inthe alloy after homogenization treatment for24h. The results prove that the phaseconstitution of Zn-4Al-0.5Ti alloy after homogenization treatment agrees well withthat in the phase diagram of the Zn-Al-Ti system.(4) When Al-5Ti-B master alloy is used to modify ZZnAl4Y alloy, the amount ofprimary α-Al phase in the alloy increases with the increase of the adding amount ofAl-5Ti-B, and the tensile strength of the alloy increases, too. When the adding amountof Al-5Ti-B is0.5wt.%, the impact toughness and the elongation of the alloy reach amaximum, respectively.(5) The modicator of Al-30wt.%Zn-5wt.%Zr-1wt.%B (Al-30Zn-5Zr-B) has goodmodification efficiency for ZZnAl4Y alloy. After modification, the tensile strength,hardness and elongation of the modified alloy increase by22.3%,17.6%and28.8%,respectively.