Effect Of Cr Alloying On Compressive Properties Of Root - Like Porous Cu

Unidirectional solidification of metal-gas eutectic (also known as "GASAR"), is a new method for producing porous materials. The porous material fabricated by this method not only has the advantages such as low the stress concentration, high mechanical properties and heat conduction ability etc, but also has anisotropic mechanical properties, high strength and modulus than that of traditional porous material. The shape of the gas pore resembles the root in lotus, and therefore also widely known as lotus-type porous materials.Although the fabrication and and properties of the lotus-type porous metal has been investigated extensively for many years, the vast majority of these research works have focused on producing gas pores in pure metal substrate. This is obviously not conducive to the application of the lotus porous metal materials, because of the low strength of pure metal. Alloying is the most effective way to improve the mechanical properties of the lotus-type porous metal materials, and is an hot research topic on the current research fields of porous metal materials.The lotus porous Cu-Cr alloys which have different Cr contents were produced successfully through controlling processing parameters (gas pressure and superheating temperature, which are also the most effective and easily controlled parameters). The effect of mushy zone width on the pore morphology and matrix are analyzed, and the results show that with the increasing of Cr, the mushy width firstly increases and then decreases. And the matrix microstructure undergoes an series variation:the bulky alpha Cu grainâ†'alpha solid solutionâ†'cellular crystalâ†'alpha dendrite and alpha+beta eutectic; In addition, the hydrogen atoms absorbed by the growing gas pore firstly increases and then decreases, and the channel that hydrogen atoms diffuse from melt into pore is getting complex, which results in an porosity increases while the average pore diameter firstly increases and then decreases.Compressive tests of lotus porous Cu-Cr alloys were carried out, and the results showed that the compressive properties of lotus porous Cu-Cr alloys depend on the Cr contents, the average pore diameter, porosity, and the angle between load direction and pore axis (ALP). The compressive stress-train curves of the porous pure Cu and Cu-Cr alloys consisted of linear elastic stage, plateau stage and densification stage. With the increasing of Cr, the densification strain and the length of plateau stage are decreased, which leads to the degradation of energy absorption ability; With the increasing of average pore diameter, the slope of compressive stress-strain curves decrease, and the Young’s modulus, the yield strength, the energy absorption per unit volume and the strain hardening index are all decreased; With the increasing of porosity, the slope of compressive stress-strain, the Young’s modulus, the yield strength value and the energy absorption per unit volume decreased,.In addition, the deformation behavior related to the angle between load direction and pores axis (ALP), and the lotus porous Cu-Cr alloy compression process has obvious anisotropic characteristics.