Preparation, Characterization And Properties Of Ni/ZK61 Bicontinuous Composites

Magnesium alloy has the advantages of low density,high specific strength,high specific elastic modulus and high heat dissipation compared with o ther metal structural materials.However,its low mechanical strength and poor wear resistance at room temperature severely limit the development of magnesium alloys in the field of lightweight structural materials.At present,domestic and foreign researchers have designed and developed a bi-continuous magnesium matrix composites.The reinforcement in the composites has a three-dimensional connected network structure,which can effectively solve the disadvantages caused by the traditional reinforcement and improve the strength and plasticity of the magnesium matrix composites.In this experiment,the high-strength magnesium alloy ZK61 was selected as the matrix,and the foamed nickel with mature technology and continuous structure was used as the reinforcement,and the Ni/ZK61 composites were prepared by spark plasma spark sintering.The microstructures interface bonding,mechanical properties and corrosion resistance of ZK61 alloy and Ni/ZK61 composites were studied by changing the sintering temperature;the formation law and mechanism of the interface reaction product between the foamed nickel and the magnesium matrix are analyzed;the strengthening and fracture damage mechanism of the Ni/ZK61 composites are discussed.The result show that :(1)With the increase of sintering temperature,the microstructure,density and mechanical properties of ZK61 alloy and Ni/ZK61 composites are also continuously improved.The microstructures and mechanical properties of N i/ZK61 composites are stronger than that of base alloy,especially the ductility is improved.When the sintering temperature is 500 ℃,the microhardness,compression strength and strain of the Ni/ZK61 are 80.4±16.7HV,371±5 MPa and 17.0±0.5%,respectively,which are4.3%,6% and 30.8% higher than the base alloy.(2)Both the nickel foam and the magnesium matrix have a three-dimensional connected network structure.This continuous distribution structure is conducive to the dispersion and transfer of stress in the composites.In addition,there is a three-dimensional interlocking mechanical interlock between the nickel foam and the magnesium matrix,which can realize effective stress transfer between the nickel foam and the magnesium matrix,avoid premature failure caused by interface cracking,and resulting in Ni/ZK61 composites have higher damage tolerance.(3)In the Ni/ZK61 bi-continuous composite material with a sintering temperature of 500℃,a certain degree of interfacial reaction occurs between the inside of the foamed nickel and the magnesium matrix,resulting in a larger diffusion area outside the foamed nickel,which reduces the contact area between the foamed nickel and the magnesium matrix,that is,the probability of galvanic corrosion is reduced,thereby improving the corrosion resistance of the overall composites.The design concept of bi-continuous composites proposes a new direction for metal matrix composites.