Hot pressing of DCPD-coated Mg-Zn-Ca powder: Corrosion behavior observed using liquid cell transmission electron microscopy

• Published in: Materials & design Vol. 226; p. 111643
• Main Authors: Tsai, Meng-Hsiu, Yang, Chia-Ming, Chen, Yen-Hsi, Chen, In-Gann, Lin, Chiu-Feng, Tseng, Chun-Chieh
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2023; Elsevier
• Subjects: Ca-P coating; Corrosion; Hydrogen release; Liquid cell transmission electron microscopy; Mg-Zn-Ca powder; Primary intermetallic phase; Ca-P coating; Primary intermetallic phase; Corrosion; Liquid cell transmission electron microscopy; Hydrogen release; Mg-Zn-Ca powder
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2023.111643

[Display omitted] •Inter-granular powder boundary with Ca-P coating fabricated with DCPD coated Mg-Zn-Ca powder using sequential hot pressing.•Bigger hydrogen bubbles causing less corrosion crack was found in Ca-P coated specimen.•Ca-P coated inter-granular powder boundary would enhance corrosion resistance.•Time dependent corrosion of Mg loss and destroyed crystalline identified by liquid cell transmission electron microscope. Mg-Zn-Ca alloys are considered potential implant materials for bone repair owing to their excellent biocompatibility and biodegradability. Typically, a dicalcium phosphate dihydrate (CaHPO4·2H2O, DCPD) coating and powder metallurgy process are adopted for biodegradable medical devices. Many literatures reported that Mg alloy surface with DCPD coating served as a barrier against the corrosion environment. However, the corrosion rate increased due to the surface coating destroyed. In this article we investigated the corrosion behavior in inter-granular powder boundary with Ca-P coating which fabricated with the DCPD-coated Mg-Zn-Ca powder using sequential hot pressing. Corrosion behavior was evaluated with hydrogen release, immersion test in DI water and liquid cell transmission electron microscopy (TEM). Hydrogen bubble rupture causing initiation of crack in the Ca-P-Mg film, showing the better corrosion resistance. In addition, the primary intermetallic (IM1) phase resisted the crack propagation that occurred on both coated and uncoated specimens. Liquid cell TEM was used to observe the time-dependent composition and crystalline changes in immersion test. The IM1 phase and Ca-P coating would enhance corrosion resistance was evaluated in less Mg element loss and destroyed crystalline. The results indicate that the Ca-P coating can decelerate the degradation of hot-pressed Mg-Zn-Ca alloys in DI water.