Additive manufacturing of biodegradable magnesium-based materials:Design strategies,properties,and biomedical applications

Magnesium(Mg)-based materials are a new generation of alloys with the exclusive ability to be biodegradable within the human/animal body.In addition to biodegradability,their inherent biocompatibility and similar-to-bone density make Mg-based alloys good candidates for fabricating surgical bioimplants for use in orthopedic and traumatology treatments.To this end,nowadays additive manufacturing(AM)along with three-dimensional(3D)printing represents a promising manufacturing technique as it allows for the integration of bioimplant design and manufacturing processes specific to given applications.Meanwhile,this technique also faces many new challenges associated with the properties of Mg-based alloys,including high chemical reactivity,potential for combustion,and low vaporization temperature.In this review article,various AM processes to fabricate biomedical implants from Mg-based alloys,along with their metallic microstructure,mechanical properties,biodegradability,biocompatibility,and antibacterial properties,as well as various post-AM treatments were critically reviewed.Also,the challenges and issues involved in AM processes from the perspectives of bioimplant design,properties,and applications were identified;the possibilities and potential scope of the Mg-based scaffolds/implants are discussed and highlighted.

Mechanical properties,corrosion behavior and biocompatibility of orthopedic pure titanium−magnesium alloy screw prepared by friction welding

The dissimilar joining of biodegradable magnesium alloy to pure commercial titanium by rotational friction welding with rotational speeds of 1100,1200 and 1300 r/min for the production of bio-screw was investigated.The metallographic analysis revealed that a good joining was obtained at the Ti/Mg alloy joint.On the magnesium alloy side,various regions such as the weld center zone(WCZ),dynamic recrystallization zone(DRX),thermo-mechanically affected zone(TMAZ)and partially deformed zone(PDZ)were observed.The highest tensile and shear strengths were 173 and 103.2 MPa,respectively at a rotational speed of 1300 r/min.The Ti/Mg alloy dissimilar friction welded joint failed at the vicinity of the intermetallic zone containing Ti3Al phase.The hardness values from the base metal magnesium alloy to the joining point increased mainly due to grain refinement(8.57μm in diameter)and the presence of titanium particles,while the hardness values were constant on the titanium side.It was also found that the corrosion rate of the Ti/Mg alloy joint was higher compared with that of the Ti and Mg alloy from the immersion studies.Additionally,the sample with a rotational speed of 1300 r/min showed better biocompatibility and a cell viability of 98.12%due to better corrosion resistance.

Role of interlayer composition in microstructure and mechanical properties during TLP bonding of GTD-111/IN-718 superalloys

An investigation was carried out to assess the applicability of transient liquid phase bonding of two dissimilar super-alloys with different interlayers. The effect of using three types of interlayer such as BNi-2, BNi-3, and BNi-9 on microstructure and mechanical properties was studied in the GTD-111/IN-718 system at 1100 ℃ for different bonding time. To determine the compositional changes and microstructure in the joint region, field emission scanning electron microscopy equipped with energy dispersive spectroscopy was utilized. The formation of Ni_(3)B in the athermally solidified zone(ASZ) is controlled by the B content and, accordingly, the morphology of Ni_(3)Si is governed by the Si content. The Cr content might impede the relocation of B from the interlayer into the base metal and the formation of CrB inside the ASZ is dominated by the Cr content. The high micro-hardness of the eutectic compounds is originated from the formation of boride matrixes such as Ni or Cr boride. The shear strength of the joint using BNi-9 after the completion of isothermal solidification is lower compared that that using BNi-3 and BNi-2, which could be related to the absence of Si in the filler metals constituent and the significant presence of Cr in BNi-9.

Synthesis of a NiTi_(2)–AlNi–Al_(2)O_(3) nanocomposite by mechanical alloying and heat treatment of Al–TiO_(2)–NiO

The aim of the present study was to investigate the phases formed during ball milling of Al–TiO_2–NiO. For this purpose, a mixture of Al–TiO_2–NiO with a molar ratio of 6:1:1 was used. Characterization of the milled powders by X-ray diffraction, differential thermal analysis, field-emission scanning electron microscopy, and transmission electron microscopy showed the formation of nanocrystalline NiTi_2 along with AlNi. A thermodynamical investigation confirmed that NiO was reduced by Al during ball milling, which consequently promoted TiO_2 reduction and the formation of NiTi_2. Al is capable of reducing NiO either during ball milling or at temperatures above the melting point of Al; by contrast, TiO_2 can be reduced by Al only by milling.