Porous Structure Design,preparation And Properties Of Ordered Porous Aluminum Materials

Porous metals are a kind of materials with structural properties and functional properties,which have wide application and good prospect in many industrial fields such as aerospace,military industry,vehicle transportation and biomedicine.Compared with random porous metals,ordered porous metals have regular structures with excellent designability and controllability,which is conducive to optimizing the performance and expanding the application of ordered porous metals.Therefore,the structural design of ordered porous metals must be the focus of research in this field.Structural design is an important method to optimize the mechanical properties of ordered porous metals,while introducing filler into the ordered porous structure to replace the original gas phase and obtain the co-continuous interpenetrating structure composites based on ordered porous metals is another important and effective strengthening method.As a kind of lightweight structural materials,ordered porous metals can be used to fill thin-walled tubes to become lightweight composite components,which further expands the engineering application of ordered porous metals.It is difficult to prepare ordered porous metals only by traditional preparation methods,but the rapid development of additive manufacturing technology provides a new opportunity to prepare ordered porous metals by traditional methods.Study on the preparation method of ordered porous metals is the basis of structural design and performance optimization of ordered porous metals.From the above,it is of great significance to carry out related investigations on the design,fabrication and property of ordered porous metals.In this study,an indirect additive manufacturing method was proposed to solve the problem of preparing ordered porous aluminum.The three-dimensional structure of ordered porous aluminum was designed to strengthen the role of stretching-dominated mechanism.The intermetallic compound Mg₁₇Al₁₂ was used to fill ordered porous aluminum and the Mg₁₇Al₁₂/AI ordered structure composites were prepared.The ordered porous aluminum was introduced into the thin-walled aluminum tube to prepare the ordered porous aluminum filled tubes.The details are as follows:(1)According to the structural characteristics of ordered porous aluminum,an indirect additive manufacturing method combining selective laser sintering technology and infiltration casting technology was proposed to successfully prepare ordered porous aluminum only under gravity condition.This method has the advantages of wide material adaptability,low laser power,low cost,high dimensional accuracy and suitable for large size structure preparation.The size error of ordered porous aluminum prepared by the indirect additive manufacturing method is analysed.It is found that the porosity of ordered porous aluminum specimen is higher than the corresponding porosity of design model.The direction of size change is identical in the preparation step and the size error mainly comes from the size difference between the resin-coated sand preform and the preform model,which is caused by the binding of resin-coated sand.The effects of matrix material on the mechanical properties of ordered porous aluminum are as follows:the compressive stress-strain curve of pure Al-based ordered porous aluminum shows a steady and continuous rising trend,while the ZL1 11-based ordered porous aluminum sample has several peaks with obvious fluctuation of the plateau area.The infiltration temperature has little effect on the compressive properties of pure Al-based ordered porous aluminum,but it has great effect on the compressive properties of ZL111-based ordered porous aluminum.(2)The basic cubic ordered porous aluminum,high-density cubic ordered porous aluminum,uniform joint strengthened ordered porous aluminum and graded joint strengthened ordered porous aluminum were all prepared by indirect additive manufacturing method.The effect of structural strengthening design on the compressive properties of ordered porous aluminum was studied.The quasi-static compression test results show that pure Al-based ordered porous aluminum has good plasticity but low strength and energy absorption capacity.Pure Al-based high-density cubic ordered porous aluminum has better compressive properties.The compressive strength is 11.3MPa and the plateau stress is 39.4MPa.However,its energy absorption performance is not outstanding due to the narrow plateau area and low densification strain.The deformation mechanism of pure Al-based ordered porous aluminum is gradually transformed from the initial stretching-dominated mechanism to the bending-dominated mechanism.ZL111-based ordered porous aluminum has higher compressive strength and specific compressive strength.ZL111-based high-density cubic ordered porous aluminum has the highest compressive strength of 86.5MPa and plateau stress of 47.3MPa.ZL111-based uniform joint strengthened ordered porous aluminum has the highest specific compressive strength,while ZL111-based graded joint strengthened ordered porous aluminum has the highest specific plateau stress.ZL111-based high-density ordered porous aluminum has the optimal energy absorption capacity and energy absorption efficiency.Due to the fracture of struts and joints,the deformation mechanism of ZL111-based ordered porous aluminum is mainly stretching-dominated mechanism.(3)The basic cubic and uniform joint strengthened pure Al-based ordered porous aluminum were used as the matrix skeleton of infiltration casting.The intermetallic compound Mg₁₇Al₁₂ was filled only under gravity condition to prepare the co-continuous interpenetrating Mg₁₇Al₁₂/Al ordered structure composites.The effect of structural design on the compressive properties of Mg₁₇Al₁₂/Al ordered structure composites was investigated.The quasi-static compression test results of co-continuous interpenetrating Mg₁₇Al₁₂/Al ordered structure composites show that the compressive properties and energy absorption capacity of Mg₁₇Al₁₂/Al ordered structure composites are better than that of ordered porous aluminum and Mg₁₇Al₁₂/Al composites with random structure.The stress-strain curve has an obvious linear elastic stage.The ordered structure can improve the compressive properties and energy absorption behaviour.Compared with the basic cubic Mg17A12/Al ordered structure composites,the uniform joint strengthened Mg₁₇Al₁₂/Al ordered structure composites show better compressive properties(compressive strength 87.6MPa and plateau stress 54.6MPa)and energy absorption behaviour.As the matrix skeleton,the uniform joint strengthened ordered porous aluminum has a stronger constraint on the filler of Mg₁₇Al₁₂,which is conducive to improving the mechanical properties.(4)The preparation process of in-situ ordered porous aluminum filled thin-walled tubes was optimized by the SiPESC integrated computing platform and in-situ ordered porous aluminum filled thin-walled tubes were prepared successfully.Ex-situ ordered porous aluminum filled thin-walled tubes with different filling forms were prepared by inserting ordered porous aluminum directly into thin-walled tubes.The compressive properties of in-situ and ex-situ ordered porous aluminum filled tubes were investigated.The results of quasi-static compression test show that the compressive properties of the ex-situ ordered porous aluminum filled thin-walled tubes are superior to that of the empty tube and the in-situ ordered porous aluminum filled thin-walled tube.The filler type,filling ratio and filling position can control the compressive properties and energy absorption behavior of ex-situ ordered porous aluminum filled thin-walled tubes.As the filler of thin-wall tubes,ordered porous aluminum with uniform joint strengthening structure is conducive to obtaining excellent compressive properties(compressive strength 82.2MPa and plateau stress 50.6MPa)and energy absorption behavior.Compared with the ex-situ ordered porous aluminum horizontally filled thin-walled tubes,the ex-situ ordered porous aluminum vertically filled thin-walled tubes show superior energy absorption behavior.The interaction between the thin-walled tube and the ordered porous aluminum filler depends on the different filling forms,which has an important influence(1+1>2)on the improvement of the compressive properties and energy absorption behavior of the ex-situ ordered porous aluminum filled thin-walled tubes.