| Zinc copper titanium alloys are called creep resistance zinc alloy for excellent creep properties compared with zinc and zinc aluminum alloys. What’s more, because their mechanical properties are comparable to copper alloys and aluminum alloys, they can partly replace them. However, zinc alloy usually exhibit such phenomenon as degradation of mechanical performance, change in size due to corrosion after serving for a long time. On the other hand, the working process of zinc alloys is difficult because of its bad plasticity. They are two important questions which restrict the industrialization and application of zinc alloys. Therefore, it is of great sense to do research on corrosion behavior and hot processing behavior of zinc alloys.A serial of Zn-1.0Cu-0.2Ti and Zn-1.0Cu-0.2Ti-X(ZCT、ZCT-X for short)alloys, were prepared by melting, casting and extruding in this paper. With the help of optical microscope, X-ray diffraction instrument, scanning electron microscope, electron probe microanalyzer, electron diffraction spectrometer and electronic universal testing machine, Microstructure and performance of microalloyed ZCT alloys were first analyzed, and then corrosion behaviors of ZCT-X alloys under different conditions were investigated. The surface appearance, corrosion products and corrosion mechanism were analyzed. According to hot compression, the flow stress equation of ZCT-0.1Cr alloy was obtained. The hot processing map of ZCT-0.1Cr was established. The mechanism of microstructure transformation during hot working was investigated. The conclusions are as follows:(1) The microstructure of as-cast ZCT alloy is typical dendrite shape. ZCT alloy is mainly constituted of η phase、TiZn15phase、εphase and Cu2TiZn22phase. Microstructure of ZCT-X is coarser than ZCT alloy, but there is no big change of phase composition. The directionality of dendrite decreases at first and then increases with the increase of Cr concentration. The directionality of dendrite decreases with the increase of Mg concentration. (2) Cr and Mg both have significantly enhanced ZCT alloy’s strength. Cr has little influence on elongation of alloy, while Mg reduces elongation of alloy significantly. Tensile fracture of ZCT and ZCT-0.1Cr are typical ductile fracture, but ZCT-0.1Mg is typical brittle fracture.(3) Electrochemical corrosion property of ZCT alloy decreases with the increase of NaCl concentration and rise of temperature. Corrosion property of ZCT alloy in tap water is better than that in NaCl solution.(4) The growing speed of corrosion rates of ZCT-X alloy in3.5%NaCl solution at room temperature slows down with time. Corrosion weightlessness rate of ZCT alloy at high temperature obeys kinetic equation. Corrosion products ZCT-X alloy in3.5%NaCl solution at room temperature are ZnO and Zn5(OH)8Cl2·H2O. While that of ZCT alloy in3.5%NaCl solution at90℃is ZnO.(5) In corrosion process of ZCT-X alloy, micro batteries are formed(η phase as anode, second phase as cathode), causing the quick dissolve of matrix. The addition of Cr、Mg have slowed down corrosion rate of alloy in tap water and NaCl solution. The effect of Mg in improving alloy’s corrosion resistance performance is more significant.(6) In the range from200to350℃and strain rates from0.01to10s-1,the flow stress and peak stress of ZCT-0.1Cr alloy increases with decrease of temperature and the increase of strain rate. Flow stress constitutive equation of this alloy is obtained (refer to equation (5-10)).(7) The instability regions in hot processing map doesn’t occur destructive structural change. Dynamic recrystallization occurs on the condition of250to350℃and0.01to0.135s-1,while on other condition only dislocation motion or dynamic recovery have occurred. During hot working of ZCT-0.1Cr alloy, deformation temperature should be controlled from250to300℃, strain rate should be controlled at about0.1s-1. |
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