Study On Mechanical Properties Of Porous Structure Of CuCrZr Alloy Formed By Selective Laser Melting

Copper alloys have excellent electrical conductivity(second only to silver in all metals),thermal conductivity(thermal conductivity up to 420W/(m * k))and excellent friction reduction and wear resistance,which can meet the needs of different fields.The porous structure of copper alloy is a new type of multifunctional structure with both structural and functional properties.Selective laser melting technology(SLM)has some advantages in the fabrication of Periodic porous structures with Triply Periodic Minimal Surfaces(TPMS).Based on the Selective laser melting technology(SLM),the static and dynamic mechanical properties of Diamond structure and Gyroid structure are studied in this paper,The effects of different heat treatment processes on the mechanical properties of porous structures are analyzed.The porous structure is designed parameterized by implicit function driving,and the control of performance is realized by changing the cell type and relative density,based on selective laser melting technology,MATLAB parameterized programming,finite element simulation,microstructure analysis and mechanical testing,A systematic research on porous structure is carried out.The main work carried out and some of the results achieved in this paper are as follows:(1)The design of TPMS porous structure.First,the TPMS surface model space is determined,and the points in the model space are traversed sequentially based on the TPMS function expression,and then the points in the space are substituted into the functions for evaluation,the points which satisfy the requirement of functional equivalence are spliced into polygons according to certain rules to approach the isosurface.Finally,the polygons are synthesized into an approximate model of TPMS surface.(2)Study on microstructure and mechanical properties of CuCrZr solid formed by SLM.By analyzing the microstructure of CuCrZr alloy,it is found that the grain of CuCrZr alloy formed by SLM has obvious ductility growth along the machining direction,which shows that(3)there are columnar crystals with length about 8μm and width about 2.5μm on the side surface,the growth trend is parallel to the processing direction.The microstructure of the samples did not change obviously after heat treatment.After 50% compression,the larger epitaxial grains disappear and become smaller irregular grains when the microstructure in XZ plane is observed.A quasi-static compression numerical model of Diamond structure and Gyroid structure was established,and the stress distribution of each structure under the same displacement load was compared.The results of compression experiments were explained and theoretical basis was provided.(4)Study on mechanical properties of porous structure of CuCrZr alloy formed by SLM.Gyroid porous structures and Diamond porous structures with different volume fractions were designed based on a Three period minimal surface(TPMS).Then,the relationship between mechanical properties and volume fractions of porous structures,as well as the failure modes and energy absorption characteristics of porous structures,were studied under different strain rate loading conditions.A Gibson Ashby model for mechanical properties and volume fraction was established.(5)Study on the influence of heat treatment process on the mechanical properties of CuCrZr alloy porous structure.The prepared porous structure was post treated by direct aging to further seek better mechanical properties.Set up three different heat treatment processes(heating to 400 ℃,450 ℃,and 500 ℃ for 1 hour each for air cooling).Under different heat treatment conditions,the mechanical properties such as elastic modulus and yield strength during compression of CuCrZr alloy porous structures have significantly improved compared to normal temperature conditions.Under the same conditions,the yield strength and elastic modulus of Diamond porous structures are superior to those of Gyroid porous structures.