Research On Preparation Of Cu-based Memory Alloy Powder Core Wire And Its Arc Additive Manufacturing Characteristics

Additive manufacturing of shape memory alloys is an important research topic in the field of smart materials.In this paper,aiming at the problem of large memory loss in the shape memory alloy additive manufacturing process,on the basis of reviewing the relevant research status at home and abroad and the previous research of the research group,put forward the research idea of "powder core wire wrapped with low boiling point alloy element powder with high boiling point skin as additive material for manufacturing shape memory alloy".Targeting Cu-based memory alloys with excellent shape memory properties,low prices,good electrical and thermal conductivity properties,wide adjustable range of phase transition points,etc.The study on the preparation of Cu-based memory alloy powder core wire and its arc-additive manufacturing characteristics is aimed at providing technical support for enriching and developing materials for additive manufacturing,and also promoting the further widespread application of Cu-based memory alloys in engineering practiceThe main work completed and results achieved in this article are as follows(1)The design model of the raw material batching scheme under different filling rates of the ternary alloy powder core wire prepared by the round tube method is established.By analyzing the requirements of "equal mass ratio","equal volume" and "filled powder density" in the drawing process,which are satisfied by the powder core wire metal round tube and the filled powder,established the design model of the raw material batching scheme under different filling rates of the ternary alloy powder core wire prepared by the round tube method,and applied this model to the powder filling process of Cu-Al-Ni memory alloy powder core wire.Combined with the actual material acquisition conditions,the actual material parameters of the Cu-14Al-4Ni memory alloy powder core wire with a theoretical filling rate of 20%,a target outer diameter of Φ2mm,and a weight of 15g were obtained under the experimental conditions in this paper.(2)The drawing process of Cu-based memory alloy powder core wire was analyzed Established The finite element model of the multi-pass drawing process of Cu-based memory alloy powder core wire,and the influence of the drawing process parameters on the stability of the powder filling rate and the distribution of the equivalent stress and strain and the residual stress in the powder core wire during the drawing deformation were studied The study found that a larger amount of pass deformation shows a lower stress-strain gradient and a smoother trend of residual stress in all directions.At the same time,the preparation process parameters of the Cu-based memory alloy powder core wire required for the research in this paper are obtained,that is,the mold half cone angle δ is 4°,the length of the sizing belt l is 3.5 mm,the drawing speed v is 500 mm/s and the average pass deformation is 14%(3)The process parameters of Cu-based memory alloy manufactured by powder-core wire arc additive are optimized.The multi-layer single-pass finite element model of Cu-based memory alloy powder core wire arc additive manufacturing was established,and the temperature variation law of each characteristic point of different deposits was studied,and optimized the process parameters of Cu-based memory alloy powder core wire arc additive manufacturing.Studies have shown that during multiple fused deposition processes,the temperature of each deposited layer continues to rise as the deposition progresses,and the highest temperature of the top layer(the third layer)is close to 3500 0 C.At the same time,the optimal process parameters for Cu-based memory alloys produced by powder core wire arc additive under the experimental conditions in this paper are the deposition speed of 6mm/s,the deposition current of 170A,and the interlayer waiting time of 30s(4)The microstructure of single-pass three-layer Cu-Al-Ni memory alloy manufactured by powder core wire arc additive manufacturing was investigated,and its memory performance was analyzed based on the structure characteristics.At the same time,the effect of nano-Ni doping with different contents on Cu-based memory alloys manufactured by powder core wire arc additive manufacturing was initially explored Studies have shown that there is severe composition segregation in Cu-based memory alloys manufactured by arc additive.Homogenization annealing can effectively eliminate composition segregation but the alloy grains are coarse.In addition,the martensite morphology under quenching is not as expected;Nano-Ni doping is helpful to eliminate the segregation of the as-deposited components,the grains are refined,and the orientation of the martensite variants in the quenched state is consistent,and the interface is clearly distinguishable.Among them,0.5wt.%nano-doping is the best.