Effect of the Ca2Mg6Zn3 Phase on the Corrosion Behavior of Biodegradable Mg-4.0Zn-0.2Mn-xCa Alloys in Hank’s Solution

Abstract

The effect of the Ca2Mg6Zn3 phase on the corrosion behavior of biodegradable Mg-4.0Zn-0.2Mn-xCa (ZM-xCa, x = 0.1, 0.3, 0.5 and 1.0 wt.%) alloys in Hank’s solution was investigated with respect to phase spacing, morphology, distribution and volume fraction. With the increase in Ca addition, the volume fraction of the Ca2Mg6Zn3 phase increased from 2.5% to 7.6%, while its spacing declined monotonically from 43 μm to 30 μm. The Volta potentials of secondary phases relative to the Mg matrix were measured by using scanning kelvin probe force microscopy (SKPFM). The results show that the Volta potential of the intragranular spherical Ca2Mg6Zn3 phase (+109 mV) was higher than that of the dendritic Ca2Mg6Zn3 phase (+80 mV). It is suggested that the Ca2Mg6Zn3 acted as a cathode to accelerate the corrosion process due to the micro-galvanic effect. The corrosion preferred to occur around the spherical Ca2Mg6Zn3 phase at the early stage and developed into the intragranular region. The corrosion rate increased slightly with increasing Ca content from 0.1 wt.% to 0.5 wt.% because of the enhanced micro-galvanic corrosion effect. The decrease in the phase spacing and sharp increase in the secondary phase content resulted in a dramatic increase in the corrosion rate of the ZM-1.0Ca alloy.

The in vivo and in vitro corrosion behavior of MgO/Mg-Zn-Ca composite with different Zn/Ca ratio

“…With further increase Ca content, the Mg 2 Ca phase starts to precipitate out from the alloy matrix, and the main second phases are mainly Mg 2 Ca + Ca 2 Mg 6 Zn 3 phase when the Zn/Ca mass ratio is below 2. For the above three types of second phases, the potential of Ca 2 Mg 6 Zn 3 phase is about 80 mV higher than that of the matrix (Fu et al, 2022), which has the smallest potential difference among these second phases. Therefore, avoiding the formation of MgZn phase in Mg-Zn-Ca alloy and increasing the proportion of Ca 2 Mg 6 Zn 3 phase will help to improve the corrosion resistance of Mg-Zn-Ca alloy.…”

Producing Zones of Enhanced Passivation on the Surface of a Biodegradable Magnesium Alloy

“…Роль частиц вторичных фаз и примесных включений в процессе коррозии магниевых сплавов долгое время является предметом оживленных дискуссий. Традиционно считается, что фазы, обладающие более положительным электродным потенциалом по отношению к магнию [1,2], негативно влияют на скорость коррозии и склонность к образованию язв, поскольку за счет гальванического эффекта [3] между ними и матрицей инициируется электрохимическая коррозия [2,3]. Однако это не всегда так.…”

Effect of CaO Content and Annealing Treatment on the Room-Temperature Mechanical Properties of AZ61 and AZ61-CaO Alloys

“…Therefore, other elements, such as calcium, are added, thereby creating thermally stable intermetallic particles with Al (Al 2 Ca) and limiting the formation of the thermally unstable Mg 17 Al 12 phase. It has previously been shown that the addition of Ca in AZ31 Mg alloy softened prismatic slips and the difference between CRSS basal and CRSS prismatic decreased considerably [34,[44][45][46][47][48][49][50]. Although Ca is relatively more cost-effective than RE elements, it is crucial to consider that both the extraction of elemental Ca and the integration of Mg-Ca master alloy can increase production costs.…”