Preparation and properties of open-cell zinc foams as human bone substitute material

Foamed zinc was prepared by infiltration casting process.The mechanical properties and corrosion resistance of the samples were studied,and the feasibility of the foamed zinc as a bone implant material was discussed.All the compression stress-strain curves of open-cell zinc foams with various cell size(1-4 mm)and porosity(55%-67%)show three stages:elastic stage,plastic stage,and densification stage.The compression strength increases with decreasing density.The smooth stress-strain response indicates a progressively deformation of open-cell zinc foam.In addition,the cell wall or edge bending and fracture are the dominated mechanisms for failure of open cell zinc foam.The immersion test for determining the corrosion rate of open cell zinc foam was conducted in simulated body fluid.It was found that zinc foam with a small cell size and high porosity showed a higher corrosion rate.In addition,open-cell zinc foams can effectively induce Ca-P deposition in immersion tests,showing good bioactivity.Therefore,the open cell zinc foam prepared in this experiment has a good potential application as a human bone substitute material.

Asymmetry in interface and bending property of Al/Cu/Al bimetallic laminates

This work was aimed to study the interfacial microstructures and three-point bending properties of Al/Cu/Al bimetallic laminates produced by the asymmetrical roll bonding and annealing. It is found that the microstructure and bonding strength of the Al/Cu interface are different with those of the Cu/Al interface. The interfacial microstructure of Cu/Al interface is improved due to the large interfacial plastic deformation caused by the different rotation speeds of roll in the asymmetrical roll bonding process. The bonding strength between Al and Cu layer can be enhanced by the moderate atomic diffusion, but is dramatically depressed by the formation of intermetallic compounds in the interface.The bending strength of bimetallic laminates is enhanced when the Cu/Al interface is loaded in tension because of the improvement of stress transition and damping by the Cu/Al interface during the three-point bending deformation. The bending fracture reveals that the interfacial cracks can be inhibited from the restricted stress concentration in the improved Cu/Al interface.

Deformation behavior and crack propagation on interface of Al/Cu laminated composites in uniaxial tensile test

The microstructural characterization and uniaxial tensile tests of Al/Cu laminated composites were taken to investigate the interface effect and fracture process of the composites.The electron microscopic graphs before and after tensile test were used to evaluate the fracture behavior.Experimental results show that the fracture surfaces of laminated composites mainly present brittle failure characteristics,accompanied with several dimples on the matrixes and a few tearing on the interface.Cracks generally initiate from the interfacial interlayer and variously propagate depending on the interfacial bonding.It is found that Cu/Al interface with enhanced bonding strength generally hinders the propagation of interlayer cracks,while the interface with weak bonding delaminates by the cracks propagation through the interfacial defects.The additional shear stress on the interface between Cu and Al layers due to their different tensile ductilities aggravates the interfacial propagation of cracks.The local plastic deformation of individual matrix layer then occurs after cracks coalesce and failure in the interface.Therefore,the strong bonding interface and matching properties between individual matrix layers are required to improve the fracture performance of Al/Cu laminated composites.