Processing technology of aa6026 extrusions -&tailoring the properties using a single step or secondary aging procedures

The aim of this project is to establish a reliable manufacturing procedure for the eco-friendly aa6026 alloy extrusions, and develop a product that would meet requirements of high strength and improved toughness, good machinability, corrosion stability, anodizing response and weldability.

Properties of wrought AA6xxx (Al-Mg-Si-X) alloys such as high strength-to-weight ratio, good formability and machinability, as well as weldability and corrosion resistance, make them suitable for a number of applications as diverse as use as architectural components, electrical parts and especially in the transportation industry for automobile, rail, metro, marine or aircraft structures. However, some of those alloys contain higher concentration of lead (Pb), that is added to improve machinability, than permitted by the European environmental legislation. Alternative alloying element, low melting point tin (Sn) causes weakness and cracking of the machined parts when exposed to stress and high temperature. Recently developed alloy, designated as AA6026 has Pb content below 0.4 wt%, so it meets European environmental protection codes such as the 2000/53/CE-ELV in the automotive sector, or 2002/95/CE-RoHS for the electrical and electronics sector. AA6026 is a medium strength alloy, excellent for being machined on high speed automatic lathes. It has good corrosion resistance and is suitable for anodizing. In addition, AA6026 does not contain tin (Sn). This eco-friendly alloy has prospect of replacing a number of alloys from AA6XXX series, like AA6061, AA6082, AA6064A, AA6042, AA6262, AA6012 and even some of Al-Cu alloys (AA2007, AA2011 and AA2030). In this project, we plan to define processing conditions (casting, homogenization, extrusion, quenching and ageing conditions) and establish the optimal manufacturing procedure for industrial production of the AA6026 alloy extruded bars. The aim is to develop a product that would meet requirements of: - high strength and good machinability; - high surface quality and good anodizing response; - corrosion stability & weldability; In order to obtain desired properties following are the critical issues that will be addressed during different processing steps: - Casting: In addition to balancing Mg/Si/Fe ratio to obtain desired strength and good extrudability, Bi/Pb, the wetting agents, ratio needs to be addressed. Fine dispersion of the low melting point Bi-Pb eutectic throughout the alloy extrusion is necessity, otherwise a machining tool might come in contact with the parts that are devoid of the low melting point compound. There is limited solubility of Bi in Al even in the liquid state, so its uniform dispersion must be accomplished during the casting process. - Homogenization: Establishing conditions for complete dissolution of Mg2Si and optimum transformation of beta-AlFeSi into alpha-Al(Fe,Mn)Si. - Extrusion: Extrusion sequence is the key point to achieve a desired quenching and subsequent aging effects. It is crucial to establish a reliable extrusion practice with the optimal preheat regime - strain rate parameters, that would provide the appropriate exit temperature and microstructure. - Aging: Definition of standard artificial aging procedure for production of different tempers and considering the response to interrupted aging and secondary precipitation with the aim of improving the toughness of the alloy. In order to accomplish stated goals, a range of methods & characterization techniques will be employed: - Microstructure characterization (OM, SEM, TEM & electrical resistivity); - Mechanical testing (hardness, tensile properties and fracture toughness); - Standardized testing of machinability, surface quality and anodizing ability as well as corrosion stability and weldability; Introduction of the AA6026 as a new product of NISSAL - Aluminium Procesing plant would increase the company’s market competitiveness. Impact of the new, eco-friendly alloy lies in its potential to replace a number of AA6XXX alloys’ extrusions. The developed AA6026 extruded sections are very attractive for introduction into the constructions of trailers or motor vehicles bodies in the "Krupa Kabine" company. Besides the high strength and stiffness-to weight ratios, important advantages are related to the the high corrosive stability and high quality of colored surface after anodization.
Project ID: 
9 992
Start date: 
Project Duration: 
Project costs: 
800 000.00€
Technological Area: 
Market Area: 
Chemicals and Materials

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