Investigation on microstructures, mechanical properties, and corrosion behavior of novel biodegradable Zn-xCu-xTi alloys after hot rolling fabricated by self-developed newly gradient continuous casting

Abstract

The poor mechanical properties exhibited by pure Zn effectively prohibit its utilization as a viable material for biodegradable implants. Hence, the primary area of interest has been directed towards alloy design and process strategies of biodegradable Zn alloys. To this end, novel biodegradable Zn-xCu-xTi (Cu: x = 0.001–2.72 and Ti: x = 0.03–1.21) alloys were designed and fabricated using a gradient continuous casting method followed by homogenization and rolling. The fabricated samples were then investigated in terms of their microstructures, mechanical properties, and corrosion behavior. The results showed that the as-cast Zn-0.001Cu-0.037Ti and Zn-1.50Cu-1.06Ti alloys possess better mechanical properties and corrosion resistance. The yield strength, elongation, and highest charge transfer resistance (Rct) of Zn-0.001Cu-0.037Ti were 137 MPa, 60 %, and 2227.9 Ω, respectively. On the other hand, the Zn-1.50Cu-1.06Ti alloy exhibited 250 MPa yield strength, 12.7.% elongation, and 11113.0 Ω Rct, respectively. Higher Cu and Ti content also led to larger second phases. However, as-hot rolled Zn-1.50Cu-1.06Ti alloy displayed better mechanical properties as compared to the Zn-0.001Cu-0.037Ti alloy due to a very fine nanocrystalline structure. Furthermore, the hot-rolled Zn-xCu-xTi alloys demonstrated superior corrosion resistance compared to their as-cast counterparts, as evidenced by the analysis of the potentiodynamic polarization and electrochemical impedance spectroscopy data. This improved corrosion resistance is attributed to the refined grain size, fractured second phases which reduce both the anode and cathode areas, and the formation of protective oxide layers. Lastly, the corrosion products primarily consisted of carbon, phosphorus, calcium, and oxygen, suggesting the presence of Zn(OH)2, carbonates, and phosphates.

Keywords

• Zn-Cu-Ti alloy
• Hot rolling
• Gradient continuous casting
• Mechanical properties
• Corrosion resistance