Microstructure And Properties Of Antibacterial Al-Mg-Si Alloys

As the aluminium alloys with moderate strength, Al-Mg-Si alloys are widely used in automobile, architecture and other industries because of its properties such as low density, high corrosion resistance and excellent weldability. It will extend application of the alloys that Al-Mg-Si alloys have antimicrobial activity.In this article, several types of Al-Mg-Si-X (X=Zn, Ag, RE) alloys were prepared by addition of 1%,3%,5% of Zn,0.1%,0.5%,0.8% Ag and 0.3%,0.6%,1% of rare earth elements respectively. The antimicrobial activity was conducted by the coating film method and the colony counting method. Microstructure and properties of the Al-Mg-Si alloys containing Zn, Ag and RE were determined by optical microscopy(OM), Vickers hardness tester, differential scanning calorimetry(DSC), universal tensile testing machine, X-ray diffraction(XRD), scanning electron microscopy(SEM) and electrochemistry workstation. The experimental results showed as follows:The DSC data reveals that the addition of Zn, Ag, and rare earth doesn’t change the precipitation sequence in Al-Mg-Si alloys. The main precipitates in Al-Mg-Si-Zn alloys is Mg2Si phase. Zn accelerates the precipitation, and the exothermic peak shifts to lower temperature gradually when the Zn content is 3wt.% or less. Precipitation is inhibited when Zn content is 5%. Both Ag and RE accelerate the precipitation, but the effect of Ag is weaker than that of Zn. The exothermic peaks in DSC curve shifts to lower temperature slightly and its peak intensity increases due to the addition of RE.There are two peaks in curves of hardness response which was characterized by Vicker’ hardness. The hardness value of the first peak is lower and that of the second one is higher when the alloys were aged at 170℃. Zn strengthens Al-Mg-Si alloys when the Zn content is 3wt.% or less. The alloy contaning Zn of 3wt.% was hardened excellently and so do the alloy containing Ag of 0.5wt.%. With the increment of Ag content, the the alloys is hardened speedly, and the peak hardness is improved. The hardness of the alloys are improved slightly by addition of rare earth.The effect of Zn, Ag,or RE content on antimicrobial activity of the Al-Mg-Si alloys was determined by Coating film method and colony counting method. The antimicrobial activity were endued to Al-Mg-Si alloys by addition Zn. The antimicrobial activity is improved by aging, thus the antimicrobial rate is more than 80%. The antimicrobial activity of as cast Al-Mg-Si-Ag alloys is excellent, and antimicrobial rate of aged Al-Mg-Si-Ag alloys is 99.9%. The antimicrobial rate of aged Al-Mg-Si-RE alloys is 55%.Corrosion resistance of Al-Mg-Si alloys contaning Zn, Ag, or rare earth was conducted by electrochemistry workstation. The Tafel curves were given to calculate the corrosion potential and corrosion current. Zn improves the corrosion resistance of the alloys, but Ag decreases the corrosion resistance of Al-Mg-Si alloys. The corrosion resistance of the alloy is improved with the increment of RE content if rare earth content is in a specific range. The corrosion resistance will be damaged if the rare earth content is beyond the specific range. The corrosion resistance of the alloys is also improved by Solid-solution.Tensile properties of Al-Mg-Si alloys was researched by addition of Zn, Ag or rare earth. The racture morphology was analyzed by scanning electron microscopy(SEM). Zn can improve the tensile properties of Al-Mg-Si alloys, and with the increment of Zn, the tensile strength of the alloys increases, but the elongation reduces. The elongation of Al-Mg-Si alloy Ag reduces while the tensile strength is improved. RE had no obvious effect on the extension rate of the alloy. When the content was in the range of 0.3%-0.6%, RE can improve the tensile strength of the alloy, but more than 0.6%, the tensile strength of the alloy will decrease when the RE content is beyond 6wt.%. The tensile fracture of the Al-Mg-Si-X (X=Zn,Ag,RE) are all ductile fracture. There were lager number of dimples in the fracture. With the increment of the alloying elements (Zn,Ag or RE), dimples became shallower and fewer, and their size is nonuniform.