Research On Additive Manufacturing And Loss Suppression Characteristics Of Fe-Based Memory Alloy With Micro-Nano Powder Core Wire

It has become a key topic in the field of intelligent material manufacturing to use additive manufacturing technology to prepare memory alloy structural parts,and realize the organic integration of shape memory alloy and additive manufacturing technology.However,in the process of additive manufacturing,it is very easy to produce the problems such as burning loss of elements,coarse grains and other problems,resulting in a large loss of shape memory function.In order to solve this problem,this paper proposes that the core wire material of "high boiling point cladding low boiling point alloy element powder" is used as the additive to manufacture shape memory alloy,and the research idea of reducing the loss of memory function in the manufacturing process of shape memory alloy additive by introducing the nano effect and other modification effects by nano alloying some alloy elements in the core of the powder;at the same time,the Fe based memory alloy with the advantages of low price,stable memory effect and high strength was selected as the research object to carry out the research on the manufacture of shape memory alloy additive with micro-nano powder core wire,aiming to clarify the process of silk,manufacturing process,structure and performance of the additive,and to explore the nano components of the micro nano powder core wire to the Fe based memory alloy additive.Therefore,it can promote the wide application of Fe based memory alloy,and enrich and develop the materials for additive manufacturing,especially the powder core wire for additive manufacturing and its related theories..The main works done and the results accomplished are as follows:(1)Based on the analysis of the temperature field in the manufacturing process of Fe based memory alloy single-layer and single-layer three-layer arc additive,the parameter selection with the least influence degree of element proportion in the manufacturing process of Fe based memory alloy with arc additive is determined,and the initial process window of the manufacturing process of Fe based memory alloy with single-layer three-layer melting deposition layer is obtained,and the manufacturing process of Fe based memory alloy additive with single-layer three-layer melting deposition layer is studied The change rule of temperature field in the manufacturing process.The results show that in the process of multiple melting deposition,over 2/3 of the deposition area of the former layer has been melted and deposited,resulting in the secondary or even multiple element burning loss of Mn,Si and other elements that are easy to burn;meanwhile,in the process of the third layer melting deposition,the highest temperature of each monitoring point is close to 4000?,which will further accelerate the element burning loss.(2)The preparation of Fe based memory alloy cored wire and the manufacturing process of arc additive were studied.Through the introduction of the round tube process,the development of the tip drawing integrated drawing equipment,the calculation of the powder filling ratio model,and the high temperature anti-oxidation treatment of the steel pipe before drawing,the whole process of the preparation of the Fe based memory alloy powder core wire was obtained.At the same time,the orthogonal test optimization was adopted,and the surface smoothness and the surface smoothness grade ? of the single three-layer deposition layer were taken as the evaluation index The optimum technological parameters for the manufacture of Fe based memory alloy with micro nano powder core wire additive were determined.The results show that when current I=190 A,deposition velocity V=0.4 m/min and interlayer cooling time T=45 s,the weld bead on the alloy surface is relatively flat and smooth,the internal morphology of the sample is intact,and there are no defects such as pores,cavities and cracks.(3)The cast structure,homogenization and solid solution structure of Fe based memory alloy made of four kinds of nano silicon doped cored wire arc additives were investigated.The results show that the doping of nano silicon interrupts the growth of as cast structure,and the as cast properties are gradually eliminated with the increase of nano silicon doping,and the as cast structure is completely eliminated after homogenization and solution treatment.At the same time,compared with the memory alloy prepared by conventional micro powder cored wire,the composition of Fe based memory alloy prepared by doping 10%,30% and 50% nano silicon accounts for the total Si element respectively In addition,the burning loss of Mn element is smaller than that of the conventional core wire,and the burning loss of 30% nano silicon is reduced by 24.17%.(4)The shape memory properties of Fe based memory alloy made of four kinds of nano silicon doped cored wire arc additives were studied.By observing the microstructure before and after deformation recovery,the influence of nano silicon doping on the change of shape memory properties was explained,and the inhibition of nano silicon doping on the loss of shape memory in the manufacture of Fe based memory alloy arc additives was clarified.The results show that the shape memory performance of the doped nano silicon is improved to some extent,and the recovery rate of deformation is increased by 244% when the nano silicon which accounts for 30% of the total Si element is doped;the main inhibition effect of the nano silicon doping on the loss of shape memory performance in the additive manufacturing is to inhibit the burning loss of alloy element and the decrease and increase of alloy strength The number of ? martensite and the inhibition of irreversible ?' martensite formation are four aspects.