Abstract
The effects of second phases on microstructure, microhardness, and corrosion behavior of aged Mg-3Sn (T3) and Mg-3Sn-1Ca (TX31) alloys are investigated systematically. The thermal stability of the CaMgSn phase is higher than that of the Mg2Sn phase, and the microstructure remains essentially unchanged in the TX31 alloy after solution treatment for 28 h at 733 K. The T3 alloy exhibits double age-hardening peaks; one is 54.9 ± 2.1 HV for 7 h, and the other is 57.4 ± 2.8 HV for 15 h. However, the microhardness quickly reaches a stable value with increasing aging times in the TX31 alloy due to the no change in CaMgSn phases. It was also found by electrochemical impedance spectra that the corrosion resistance of aged T3 alloy is superior to that of aged TX31 alloy, especially T3 alloy aged for 7 h. The corrosion film of aged T3 alloy is denser, which attributes to most of dissolved Sn in the α-Mg matrix and the formation of a small quantity of tiny Mg2Sn particles, and effectively prevents the occurrence of further corrosion of the Mg matrix. However, galvanic cells formed between α-Mg and CaMgSn phases accelerate the corrosion of aged TX31 alloy.
Highlights
Magnesium (Mg) alloys, as the commercially lightest structural materials, have high strength/weight ratios, good damping capacity, and excellent thermal conductivity [1,2,3,4]
The study of the micromechanical properties mainly focuses on the variation mechanism of residual stress and fracture toughness of Mg alloy
Ast and Ghidelli et al [14,15] reviewed the micro-pillar splitting and micro-cantilever bending approaches to fracture toughness evaluation at the micro-scale, which can be used as a reference in the research of Mg alloy
Summary
Weight ratios, good damping capacity, and excellent thermal conductivity [1,2,3,4]. It has a wide range of applications in many fields, such as aerospace, transportation, automobile industries, and heat dissipation materials. The Sn element has lower diffusivity at high temperatures, appropriate solubility, and thermal-stability of the Mg2 Sn phase in the Mg alloys. Ca element forms a thermally stable CaMgSn phase (Sn/Ca weight ratio: 3/1~3.5/1) with Sn and Mg in the Mg-Sn alloy, which further improves the elevated temperature properties of the alloy [10,11,12,13]. Ast and Ghidelli et al [14,15] reviewed the micro-pillar splitting and micro-cantilever bending approaches to fracture toughness evaluation at the micro-scale, which can be used as a reference in the research of Mg alloy
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