The Effect of Equal-Channel Angular Pressing on the Microstructure, the Mechanical and Corrosion Properties and the Anti-Tumor Activity of Magnesium Alloyed with Silver

Abstract

The effect of equal-channel angular pressing (ECAP) on the microstructure, texture, mechanical properties, corrosion resistance and cytotoxicity of two magnesium-silver alloys, Mg-2.0%Ag and Mg-4.0%Ag, was studied. Their average grain size was found to be reduced to 3.2 ± 1.4 μm and 2.8 ± 1.3 μm, respectively. Despite the substantial grain refinement, a drop in the strength characteristics of the alloys was observed, which can be attributed to the formation of inclined basal texture. On a positive side, an increase in tensile ductility to ~34% for Mg-2.0%Ag and ~27% for Mg-4.0%Ag was observed. This effect can be associated with the activity of basal and prismatic slip induced by ECAP. One of the ECAP regimes tested gave rise to a drop in the corrosion resistance of both alloys. An interesting observation was a cytotoxic effect both alloys had on tumor cells in vitro. This effect was accompanied with the release of lactate dehydrogenase, an increase in oxidative stress, coupled with the induction of NO-ions and an increase in the content of such markers of apoptosis as Annexin V and Caspase 3/7. Differences in the chemical composition and the processing history-dependent microstructure of the alloys did not have any significant effect on the magnitude of their antiproliferative effect.

Degradation Analysis of Thin Mg-xAg Wires Using X-ray Near-Field Holotomography

“…Moreover, Tie et al utilized electrochemical corrosion resistance measurements for their analysis, which can only provide immediate measurements but fails to provide information on the longer term material behaviour. In agreement with the study by Estrin et al [15], in which Mg-2Ag and Mg-4Ag after T4 treatment and following equal-channel angular pressing (ECAP) were studied, we find that at early time points (2 or 3 days) the degradation rate of the different alloys after heat treatment do not differ significantly. At the same time, ECAP, which reduces the grain size and increases the number of Mg 4 Ag precipitates, similar to the recrystallized state in this study, leads to higher degradation rates in Mg-4Ag than Mg-2Ag, which is in agreement with the trends observed here.…”

“…By selecting the content of Ag accordingly, the degradation rate of the Mg-Ag system becomes controllable. For example, Estrin et al [15] adjusted the degradation rate of Mg-Ag alloys to be cytotoxic to tumour cells in in vitro tests. Processing of rolled Mg-xAg (x = 6 and 8 wt.%) sheets above the solvus temperature also enabled limiting the degradation rate in physiological media to 0.5 mm/year after 7 days [13].…”

Rationale for Processing of a Mg-Zn-Ca Alloy by Equal-Channel Angular Pressing for Use in Biodegradable Implants for Osteoreconstruction

“…It is known that ECAP can significantly improve the mechanical and in-service properties of metallic materials [35][36][37]. In the case of magnesium alloys, ECAP makes it possible to improve their strength [38] and, in addition, increase ductility due to the ECAP-induced transformation of texture [39,40]. In the past, we studied the effect of ECAP on the mechanical properties of alloy Mg-1%Zn-0.3%Ca [41].…”

The Effect of Equal-Channel Angular Pressing on Microstructure, Mechanical Properties, and Biodegradation Behavior of Magnesium Alloyed with Silver and Gadolinium

“…Studies carried out on the U2OS cancer cell line showed the effectiveness of the additions of Zn [18] and La [19] as inhibitors of cell growth, the effect being enhanced with an increase in the content of these elements. In addition, the present authors also carried out research aimed at studying the effect of the addition of rare earth elements [20] and Ag [21] on the vitality of tumor cells. These previous studies allow us to conclude that the use of magnesium alloys with an appropriate composition and degradation behavior is a promising avenue for treatment of cancer patients.…”

“…These alloys are attractive candidates for treatment of cancer patients. The earlier studies on alloys of the Mg-Ag [21,30] and Mg-Gd [31][32][33] systems showed that this deformation method is promising for the refinement of the microstructure and the associated increase in strength and ductility of alloys of these systems.…”