Study On Microstructure And Mechanical Behavior Of Lattice Structure Copper Alloy Prepared By Laser Selective Melting

Copper and copper alloys are widely used in the electronics industry due to their excellent thermal conductivity.Among them,lattice structure copper alloys have great value in the fields of battery,heat dissipation,sensing and driving,but traditional preparation methods such as investment casting and wire assembly molding and the like cannot effectively control the mechanical properties of the lattice structure.The laser selective melting(SLM)technology can realize the precise regulation of the mechanical properties of the lattice structure copper alloy through the control process,which provides a novel and efficient method for preparing the lattice structure copper alloy.Based on this,the SLM technology is used to prepare the lattice alloy copper alloy.Firstly,the parameters of the SLM preparation and heat treatment process of the selected copper alloy system are optimized to obtain the optimal preparation parameters.Then,the lattice structure copper alloy is prepared on this basis.And carry out fine/microscopic structural analysis and mechanical property test analysis to reveal the correlation of "preparation process-tissue structure-mechanical properties".In this paper,Cu-10 Sn alloy powder prepared by water atomization,the relative density of Cu-10 Sn alloy samples prepared by the optimal process parameters reached 99.7%.The microstructure of Cu-10 Sn alloy was found to be α-Cu solid solution and Cu41Sn11 intermetallic compound.The grain morphology was mainly columnar dendrites.The prepared Cu-10 Sn alloy has a yield strength of 392±6 MPa,a tensile strength at break of 749±5 MPa,and a plastic deformation of 29±2.3% under quasistatic tensile test.The comprehensive mechanical properties are superior to those of the as-cast sample.In order to further seek better mechanical properties of the printed samples,three vacuum heat treatment processes were designed,which were the first process(heated to 613 K,heated for two hours and then air cooled to room temperature),the second process(heated to 673 K,heated for four hours and then heated Heat treatment to 1073 K,finally air cooled to room temperature)and the third process(heated to 1133 K,held for two hours and then air cooled to room temperature).The microstructure of the Cu-10 Sn alloy after the first process has not changed much.The yield strength of the sample decreased to 351±4 MPa,the tensile plasticity increased slightly,and the breaking strength increased to 767±3 MPa.The grain of the Cu-10 Sn alloy after the second process is transformed into equiaxed crystal,and there is an annealed twin structure inside some grains.The yield strength of the sample decreases to 245±5 MPa,and the tensile plasticity increases to 54±1.9%.The fracture strength increased to 832±6 MPa.Most of the grains of Cu-10 Sn alloy after the third process growth occurred,and there were twin crystals inside some grains.The yield strength of the sample decreased to 175±4 MPa,tensile plasticity.Slightly increased,and the breaking strength decreased to 421 ± 5 MPa.The comprehensive comparison of the samples after the second process showed superior comprehensive mechanical properties.On this basis,by changing the length of the rod under the condition that the diameter of the lattice structure rod is constant,the body center cube(type I and type II)and diamond(type I and type II)lattice structure Cu-10 Sn alloy are respectively prepared by SLM.The surface topography and lateral morphology of the type I bodycentered cubic lattice structure and the type II body-centered cubic lattice structure are similar to those of the dense solid Cu-10 Sn alloy,and are mainly composed of columnar crystals.The yield strain interval of the type I body-centered cubic lattice structure is very small,and the entire lattice structure skeleton is deformed from the bottom,and its elastic deformation is about 4.3%,and the yield strength is about 97 MPa;With the increase of strain,the stress of the type II body-centered cubic lattice structure increases slowly,and the stress-strain platform trend is gentle and has better bearing capacity.The elastic deformation is about 4.9% and the yield strength is about 35 MPa.There is a difference between the type I diamond lattice structure and the design model,and the elastic deformation is about 2.3%,and the yield strength is about 207 MPa;In the type II diamond dot matrix structure,the roughness of the pillar or the node region is large,and the fineness of the model cannot be achieved.The elastic deformation is about 3.3%,and the yield strength is about 75 MPa.The process applicability is best through comprehensive comparison of the type II body-centered cubic lattice structure.The second process of the type II body-centered cubic lattice structure is carried out.The microstructure is dominated by equiaxed crystals,and there are twin crystal structures inside some grains,which is consistent with the results of the block samples after the second process.The mechanical properties were tested.The elastic deformation was 6.7%,the yield strength was about 45 MPa,and the stress platform area was smoother,which was beneficial to maintain a good average stress distribution during the load-bearing process,which has better process suitability.