Study On Heat Treatment Process And Forming Property Of Deformed Zn-Cu-Ti Alloy

Zn-Cu-Ti alloy is a typical deformation of zinc alloy, which has excellent creep resistance, low thermal expansion coefficient, high strength, good plasticity, easy processing, similar mechanical properties to brass. Zn-Cu-Ti alloy is mainly used in the battery casing, building materials and household hardware and other fields. Although the current applications of Zn-Cu-Ti alloy is more and more widely because of its low cost of raw materials, the forming property of the alloy need to be improved.The deformed Zn-Cu-Ti alloy was taken as the research object in this paper. The study on composition optimization,heat treatment and forming property of Zn-Cu-Ti alloys was carried out. Zn-Cu-Ti alloy ingots are prepared by ZGJL0.01-40-4 vacuum induction melting furnace. The ingots are tested under different process parameters of extrusion, rolling, and heat treatment,its purpose is to obtain Zn-Cu-Ti alloy sheets. The effects of heat treatment process on microstructure and properties of Zn-2.0Cu-0.05Ti-0.001 Mg and Zn-1.5Cu-0.08 Ti alloys were researched by optical microscope scanning, electron microscopy, X-ray diffraction, transmission electron microscope, Japan, SHIMADZ UAG-I/250 KN precision universal testing machine, BHB-80 sheet biaxial tensile testing machines, which is to determine the reasonable heat treatment process of Zn-Cu-Ti alloy. This paper study on typical forming properties of Zn-2.0Cu-0.05Ti-0.001 Mg alloy such as Erichsen test, hole expansion test, conical cup test. As the whole, the following points are considered as the main ideas:1. The reasonable proportion of the Zn-Cu-Ti alloy with excellent performance is Zn-2Cu-0.05Ti-0.001 Mg, which is determined through the orthogonal experiment. The hardness of the alloy is 88 HV, tensile strength reached to 255 MPa, the elongation rate reached to 63%.2. Zn-Cu-Ti alloy has obvious characteristics of softening after cold rolled and then hardening anneal.(1) Under different annealing temperature conditions, The change law of the hardness with the annealing time increasing shows a similar trend. The hardness has a sharp increase in 0-1h, then at relatively stable state with a slightly fluctuations within a certain range.(2) Annealing temperature has great influence on hardness, the higher the temperature, the higher hardness obtained. For Zn-2.0Cu-0.05Ti-0.001 Mg alloy, the influence of annealing temperature on the hardness is more apparent. After 240 annealed, the hardness is up to 86.82 HV, ℃ and increases by 19.3% compared to(72.77 HV) after 180 ℃annealed.(3) Annealing temperature has significant effect on tensile strength and elongation, tensile strength and elongation after 180 ℃annealed compared to unannealed has a significant change. Under the condition of annealing time for 3h, the tensile strength of Zn-2.0Cu-0.05Ti-0.001 Mg alloy increases from 200 MPa to 303 MPa, and the elongation decreases from 107% to 39%; the tensile strength of Zn-1.5Cu-0.08 Ti alloy increases from 162 MPa to 284 MPa, and the elongation decreases from 107% to 20%.(4) The influence of annealing time on tensile strength and elongation was not significant. With the extension of annealing time, the tensile strength and elongation of Zn-2.0Cu-0.05Ti-0.001 Mg alloy is fluctuating within a certain range.3. Annealing temperature has more evident effect on microstructure and property of Zn-Cu-Ti alloy than the annealing time. The reasonable heat treatment process of Zn-2.0Cu-0.05Ti-0.001 Mg alloy with higher hardness, tensile strength, good ductility, formability is annealing temperature for 180℃, annealing time for 4 hours.4. The influence of speed on the forming property In the three simulated formability testing of Erichsen, hole expansion, conical cup, The more slowly speed, the higher formability of Zn-2.0Cu-0.05Ti-0.001 Mg alloy sheet. In Erichsen test, when the speed is 1.5mm/min, IE value is up to 13.21 mm, and increases by 8.4% compared to(12.18mm) at the speed of 5mm/min. In hole expansion test, when the speed is 3mm/min, λ value is up to 133%, and increases by 84.7% compared to(72%) at the speed of 5mm/min. In conical cup test, when the speed is 3 mm/min, the minimum value of CCV is 27.28 mm, and reduces by 7.4% compared to(29.45mm) at the speed of 30mm/min.5. The influence of lubrication condition on the forming property When the speed is slowly, the lubricant condition has more obvious effects on IE, λ values, CCV values of Zn-2.0Cu-0.05Ti-0.001 Mg alloy sheet. In Erichsen test, when the speed is v ≤ 2.5mm/min, the effect of polyethylene film lubrication is better; when the speed is v ≥4.4mm/min, the effect of oil lubricant is better. In hole expansion test, when the speed is about 4mm/min, the effect of polyethylene film lubrication is better; when the speed is v ≤3mm/min, the effect of oil lubricant is better. In conical cup test, regardless of what test speed, the effect of polyethylene film lubricant is better.