The lightweighting of automobiles is a shared goal of the global automotive industry. Increasing the use of aluminum alloy materials in automotive components is the direction of development for modern new-type vehicles. 6082 aluminum alloy is a heat-treatable, strengthened aluminum alloy with moderate strength, excellent formability, weldability, fatigue resistance, and corrosion resistance. This alloy can be extruded into pipes, rods, and profiles, and it is widely used in automotive components, welded structural parts, transportation, and the construction industry.
Currently, there is limited research on 6082 aluminum alloy for use in new energy vehicles in China. Therefore, this experimental study investigates the effects of 6082 aluminum alloy element content range, extrusion process parameters, quenching methods, etc., on the alloy profile’s performance and microstructure. This study aims to optimize alloy composition and process parameters to produce 6082 aluminum alloy materials suitable for new energy vehicles.
1. Test Materials and Methods
Experimental process flow: Alloy composition ratio – Ingot melting – Ingot homogenization – Ingot sawing into billets – Extrusion of profiles – In-line quenching of profiles – Artificial aging – Preparation of test specimens.
1.1 Ingot Preparation
Within the international range of 6082 aluminum alloy compositions, three compositions were selected with narrower control ranges, labeled as 6082-/6082″, 6082-Z, with the same Si element content. Mg element content, y > z; Mn element content, x > y > z; Cr, Ti element content, x > y = z. The specific alloy composition target values are shown in Table 1. Ingot casting was performed using a semi-continuous water-cooling casting method, followed by homogenization treatment. All three ingots were homogenized using the factory’s established system at 560°C for 2 hours with water mist cooling.
1.2 Extrusion of Profiles
The extrusion process parameters were adjusted appropriately for billet heating temperature and quenching cooling rate. The cross-section of the extruded profiles is shown in Figure 1. The extrusion process parameters are shown in Table 2. The forming status of extruded profiles is shown in Figure 2.
2.Test Results and Analysis
The specific chemical composition of the 6082 aluminum alloy profiles within the three composition ranges was determined using a Swiss ARL direct reading spectrometer, as shown in Table 3.
2.1 Performance Testing
To compare, the performance of the three composition range alloy profiles with different quenching methods, identical extrusion parameters, and aging processes was examined.
2.1.1 Mechanical Performance
After artificial aging at 175°C for 8 hours, standard specimens were taken from the direction of extrusion of the profiles for tensile testing using a Shimadzu AG-X100 electronic universal testing machine. Mechanical performance after artificial aging for different compositions and quenching methods is shown in Table 4.
From Table 4, it can be seen that the mechanical performance of all profiles exceeds the national standard values. Profiles produced from 6082-Z alloy billets had lower elongation after fracture. Profiles produced from 6082-7 alloy billets had the highest mechanical performance. 6082-X alloy profiles, with different solid solution methods, exhibited higher performance with rapid cooling quenching methods.
2.1.2 Bending Performance Testing
Using an electronic universal testing machine, three-point bending tests were conducted on samples, and the bending results are shown in Figure 3. Figure 3 shows that products produced from 6082-Z alloy billets had severe orange peel on the surface and cracking on the back of the bent samples. Products produced from 6082-X alloy billets had better bending performance, smooth surfaces without orange peel, and only small cracks at positions limited by geometric conditions on the back of the bent samples.
2.1.3 High-Magnification Inspection
Samples were observed under a Carl Zeiss AX10 optical microscope for microstructure analysis. The microstructure analysis results for the three composition range alloy profiles are shown in Figure 4. Figure 4 indicates that the grain size of products produced from 6082-X rod and 6082-K alloy billets was similar, with slightly better grain size in 6082-X alloy compared to 6082-y alloy. Products produced from 6082-Z alloy billets had larger grain sizes and thicker cortex layers, which more easily led to surface orange peel and weakened internal metal bonding.
2.2 Results Analysis
Based on the above test results, it can be concluded that the design of alloy composition range significantly affects the microstructure, performance, and formability of extruded profiles. An increased Mg element content reduces alloy plasticity and leads to crack formation during extrusion. Higher Mn, Cr, and Ti content have a positive effect on refining the microstructure, which in turn positively impacts surface quality, bending performance, and overall performance.
3.Conclusion
Mg element significantly affects the mechanical performance of 6082 aluminum alloy. An increased Mg content reduces alloy plasticity and leads to crack formation during extrusion.
Mn, Cr, and Ti have a positive effect on microstructure refinement, leading to improved surface quality and bending performance of extruded products.
Different quenching cooling intensities have a noticeable impact on the performance of 6082 aluminum alloy profiles. For automotive use, adopting a quenching process of water mist followed by water spray cooling provides better mechanical performance and ensures the profiles’ shape and dimensional accuracy.
Edited by May Jiang from MAT Aluminum
Post time: Mar-26-2024
