Effect Of Mn,plastic Deformation And Heat Treatment On The Microstructure And Properties Of 6082 Aluminum Alloy

While the automotive industry is booming,due to the need for environmental protection and energy saving,automotive light-weighting has become a trend in the world.6-series aluminum alloy is a suitable material for automotive light-weighting due to its good plasticity,welding property and corrosion resistance.However,its tensile strength is at a medium level.For some profiles with high mechanical performance requirements,6-series aluminum alloy may not be able to meet the requirements,which limits its application in automotive.Most of the current research on the strength enhancement of 6-series aluminum alloys has used the addition of rare earth elements,but in practical production this is more costly.Due to the wide range of elemental content of 6082 aluminum alloy,the content of its alloying elements can be adjusted to improve tensile strength.Based on 6082 aluminum alloy,this paper improves its tensile strength by adjusting the content of Mn elements.Subsequently,a suitable homogenization system is explored to eliminate intracrystalline segregation and enhance plasticity.Then the plastic deformation of the material is carried out through hot forging to improve the organizational structure,refine the grain size and improve the strength.Finally,a suitable solution-ageing heat treatment process is carried out to further improve the strength of the profile.Ultimately,the aluminum alloy profiles which can meet the strength requirements of the project products are obtained to provide theoretical support and technical guidance for the actual production.The specific work is as follows.(1)The ingot metallurgy method was used to prepare the ingots of AA6082 alloy with different Mn element contents.It was found that the Al Mn Cr phase,Al(Mn Cr Fe)Si phase,Mg₂Si phase,Al₃Ti phase and other crystalline phases mainly existed in the alloy.The isometric degree of the alloy grains is highest when 0.8 wt.%Mn was added to the alloy,and the mechanical properties of the alloy were the best at this time.(2)The best homogenization temperature and time for AA6082 alloy is 550?×8 h.At this time,the soluble phase in the alloy is almost completely dissolved into the matrix and the plasticity of the alloy is enhanced.(3)The AA6082 alloy was hot forged after homogenization and the effect of deformation on the microstructure and properties of the alloy was investigated.The results showed that the alloy deformed by 60%plastic deformation had a uniform distribution of needle-like second phase on the grain boundaries and the mechanical properties were best.(4)To study the effect of different ageing processes on the mechanical properties of AA6082 alloy after hot forging at 60%deformation,it was concluded that the best heat treatment process for the alloy is conventional solution(550?×2 h)followed by three-stage ageing(140?×4 h+180?×3 h+140?×2 h),at this time the tensile strength can reach 337 MPa.In summary,the results of the study show that design and melting of AA6082 alloy with 0.8 wt.%Mn element content,and the ingot is subjected to homogenization treatment at 550?×8 h and hot forging deformation with 60%deformation,followed by solution treatment at 550?×2 h and ageing treatment at 140?×4 h+180?×3 h+140?×2 h,the tensile strength of the alloy can reach 337MPa,which expands its application scope in automotive parts.