Microstructure,mechanical properties and corrosion behavior of quaternary Mg−1Zn−0.2Ca−xAg alloy wires applied as degradable anastomotic nails

The microstructure,mechanical properties and corrosion behavior of quaternary degradable Mg−1Zn−0.2Ca−xAg(x=1,2,4 wt.%)alloy wires,intended as anastomotic nails,were investigated.It was found that these Ag-containing alloy wires mainly consist of Mg matrix and Ag17Mg54 phase,characterized by SEM,EDS,XRD and TEM.Tensile and knotting tests results demonstrate the superior mechanical properties of these alloy wires.Especially,Mg−1Zn−0.2Ca−4Ag alloy exhibits the highest mechanical properties,i.e.an ultimate tensile strength of 334 MPa and an elongation of 8.6%.Moreover,with increasing Ag content,the corrosion rates of these alloy wires remarkably increase due to the formation of more micro-galvanic coupling between Mg matrix and Ag17Mg54 phase,shown by mass loss and scanning Kelvin probe force microscopy(SKPFM)results.The present alloy can be completely degraded within 28 d,satisfying the property requirements of anastomotic nails.

Behavior and influence of Pband Biin Ag-Cu-Zn brazing alloy

The effects of trace content of Pb and Bi elements on the spreading property and the strength of brazed joints of Ag Cu Zn filler metal have been studied. The results show that Pb has little effect on both above properties, and Bi has remarkable influence on the spreading property but little effect on the strength of brazed joint. Pb and Bi dissolve into the Ag Cu Zn matrix and will melt and gather at lower temperature when that alloy is being heated. Therefore a liquid forms on the surface of the Ag Cu Zn alloy and overlays the melting alloy, then keeps the filler metal away from the materials being joined, and so decreases the spreading property.

Corrosion behaviour of Mg−Gd−Y−Zn−Ag alloy components with different sizes after cooling

The corrosion behaviour of Mg−6Gd−3Y−1Zn−0.3Ag(wt.%)alloy components with different sizes after cooling was investigated.The alloys in the small components(SC)cooled fast,which were composed ofα-Mg matrix and coarse long-period stacking ordered(LPSO)phases.The alloys in the large components(LC)cooled slowly,and there were thin lamellar LPSO phases precipitating inside the grains,except forα-Mg matrix and coarse LPSO phases.The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample.Electrochemical impedance spectroscopy(EIS)test showed that the surface film on LC alloys provided worse protection.The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion,which accelerated the rupture of the surface film.

Spiral-eutectic-reinforced Biodegradable Zn-Mg-Ag Alloy Prepared via Selective Laser Melting

Zn is a promising biodegradable metal owing to its moderate degradation rate and acceptable biocompatibility.However,the insufficient mechanical strength and plasticity of pure Zn limits its application in bone implants.In this study,a spiral eutectic structure is constructed in Zn-Mg-Ag alloys prepared via selective laser melting to improve their mechanical properties.Results show that the prepared Zn-Mg-Ag alloys are composed of a primary Zn matrix and a eutectic phase,which is composed of alternating𝛼-Zn and an intermetallic compound,MgZn 2.Moreover,the eutectic phase resembles a spiral and increases with Ag content in the alloys.The eutectic pinning effect hinders dislocation and hence results in dislocation accumulation.Meanwhile,the spiral structure alters the propagation direction and dissipates the propagation energy of cracks layer by layer.Consequently,a compressive strength of up to 309±15 MPa and an improved strain of 27%are exhibited in Zn-3Mg-1Ag alloy.Moreover,the Zn-Mg-Ag alloys show high biocompatibility with MG-63 cells and antibacterial activity against Escherichia coli.These findings indicate the potential of spiral eutectic structures for enhancing both the mechanical strength and plasticity of biodegradable Zn alloys.