Effect of Heat Treatment on Microstructure and Degradation Properties of Bi Microalloyed Al-Ga-Mg-Sn Aluminum Alloy

Abstract:

The as-cast Al-Ga-Mg-Sn degradable aluminum alloy was microalloyed and heat treated. Al-Ga-Mg-Sn-Bi alloy was selected for annealing and solid solution/aging treatment. The microstructure, phase composition and self-corrosion potential of Al-Ga-Mg-Sn-Bi alloy were analyzed by optical microscope, scanning electron microscope, X-ray diffractometer and electrochemical workstation. The results show that the addition of trace elements Bi and Zn reduces the self-corrosion potential of Al-Ga-Mg-Sn. The as-cast Al-Ga-Mg-Sn-Bi alloy is composed of Al matrix phase, Mg₂Sn and Mg-Ga phase, and the characteristics of fishbone dendrites are obvious at room temperature, the self-corrosion potential in 3wt% KCl solution ranges from –1.60 V to –1.49 V. With the increase in annealing temperature, dendrites decrease, and disappear at 500 ℃. Mg₂Sn and Mg-Ga phases are precipitated after solid-solution/aging treatment. Compared with as-cast Al-Ga-Mg-Sn-Bi alloy, the hardness of alloy after annealing treatment decreases. Whereas, hardness of alloy after solution/aging treatment increases. Compared with as-cast Al-Ga-Mg-Sn-Bi alloy, the degradation rates of alloy after both solution/aging treatment and annealing treatment reduce.