| 6016 aluminum alloy is currently one of the most widely used alloys for body panels,and it is a heat-treatable aluminum alloy.After bake hardening,the performance of the alloy is greatly improved to meet the application’s anti-sag resistance,and at the same time have good corrosion resistance.It usually takes up to several months from the completion of aluminum preparation to the actual application of vehicle parts.During this period,the material will undergo a very significant natural aging phenomenon,which will reduce its formability and paint hardening performance.Therefore,it is usually necessary to pre-age the alloy sheet before leaving the factory to suppress the harmful effects of natural aging.At present,a large number of laboratory-based short-term high-temperature pre-aging studies at a fixed temperature have obtained good results,but the laboratory-based conclusions are quite different from industrial production and cannot be adopted by enterprises.Therefore,the pretreatment process simulation for the actual industrial production process and the organization and performance research of the materials at each time node are helpful to optimize the actual production process and provide feasible guidance for factory production.In this experiment,commercial 6016 aluminum alloy is the research object,based on the industrial heat treatment process,a series of two-stage pre-aging processes are simulated and designed,the microstructure of the alloy is characterized by DSC,SEM,TEM and other characterization methods,and the heat treatment is performed.The hardness,tensile properties,flanging properties,electrical conductivity,and n/r value of the post alloy were tested.The influence of different pre-aging temperatures on the forming properties and bending properties of the alloy is analyzed,and the main conclusions are as follows:(1)In the temperature range of 80℃+75℃/8h,85℃+75℃/8h,95℃+75℃/8h,the T4 P state hardness of the sample after the first pre-ageing in the temperature range of80℃+75℃/8h is lower,the formability is better,and the bending performance is also good.Meet the requirements.Even in the long-term natural aging(3 months),the temperature range of 80-90℃ can also meet the performance requirements,providing practical guidance for the optimization of the actual production process of the factory and the stable production of sheet products.(2)After all samples are left at room temperature for 2 weeks and 3 months,the overall yield strength and tensile strength of the samples are not much different,but the103℃+75℃/8h sample is the highest.When the samples at 95℃+75℃/8h and103℃+75℃/8h are naturally aged for 2 weeks and 3 months,the bake hardening increments are quite different.Therefore,the higher the first-stage pre-aging temperature is,the more sensitive the natural aging time is.(3)The r and n values of the samples at 80℃+75℃/8h and 95℃+75℃/8h in the direction of 90° are higher than those in the direction of 0°.In order to obtain better n and r values,the S texture should be reduced and the percentage content between the textures should be uniform.The pre-aging temperature has no obvious effect on the texture.(4)After baking and hardening for 30 minutes,the precipitation phase distribution of the samples at 95℃+75℃/8h and 103℃+75℃/8h is relatively dense,while the samples after solution quenching without pre-aging are directly parked for 2weeks.Less,its bake hardening effect is the worst.After bake hardening for 10 minutes,the precipitated phases in the sample are more sparse,indicating that even after the two-stage dynamic pre-aging process,the bake hardening time cannot be shortened. |
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