Investigation of heat treatment and subsequently surface modification by nano-TiO2 on Mg–Zn–Ca–Mn bio-magnesium alloy

Abstract

The microstructure and mechanical properties of Mg–2Zn–0.5Ca–1.0Mn alloy under different treatments were investigated. Nano-TiO2 with biological activity was added to the self-optimized silicate electrolyte in order to enhance the corrosion resistance and the activity of micro-arc oxidation (MAO) coatings formed in the aged bio-magnesium alloy silicate electrolyte. Results show that the tensile strength and micro-hardness of solution treatment alloy were 194 MPa and 40.55 HV, respectively, which were increased by 11% and 30% comparing with as-cast alloy. Subsequently, the experimental alloy was aged at 175 °C from 0.5 h to 36 h, the tensile strength of the alloy reached 229 MPa when the alloy was aged to 16 h, which was 55 MPa higher than the as-cast alloy. Besides, the fracture mechanism transformed from the cleavage fracture to quasi-cleavage fracture after heat treatment. Different content of modified nano-TiO2 (1, 3 and 5 g/L) is added into based silicate electrolyte has been utilized to modify the bio-magnesium coatings for precoated metals. The sealing processes on MAO coatings surface effectively improve the corrosion resistance property of the bio-magnesium alloy. As the concentration of nano-TiO2 increases from 0 g/L to 5 g/L, the corrosion potential of MAO ceramic film increases gradually. When the concentration of nano-TiO2 is 5 g/L, the corrosion potential of the formed ceramic film is the highest, reaching – 1.3601 V, this shows that the ceramic membrane has good corrosion resistance.