电子束增材制造钛合金的组织特征与拉伸性能研究
发布时间：2018-10-26 12:46
【摘要】：钛合金由于其性能优势,在航空航天领域得到广泛的应用,同时增材制造技术在复杂结构零件成型、减少加工程序、缩短加工周期等方面具有明显的优势,在先进制造技术领域有较好的应用前景。而电子束增材制造技术作为一种新型技术,在成型件组织、力学性能等方面还有待进一步探究。因此,本文以TA3、TB5、TC4钛合金作为基材,对电子束增材制造钛合金进行了研究,分析了送丝速度、送丝方式及束流强度对单道多层成型的影响;在此基础上研究了单道多层组织及力学性能的变化规律,并着重分析了基材类型对成型件组织、硬度及拉伸强度的影响及成型层-基材界面处的拉伸性能变化规律。影响单道多层成型的工艺参数主要有送丝速度、沉积方式和束流强度。当送丝速度Vs=20mm/s时,适当减少束流并结合单、双向沉积方式可得到60层单壁试样。单壁试样成型层上有明显的熔凝线纹路及层带形貌特征,其组织为条状α相及残余β组成的网篮状组织,显微硬度值在260HV~300HV之间波动,网篮状组织尺寸及成型层硬度值均以成型高度5mm为一个单位呈现周期性变化。堆积层数低于5层时,成型层组织为沿外延生长的粗大β柱状晶,柱状晶内为α相及残余β相组成网篮状组织,随着成型层数的增多,柱状晶的长度和宽度均增大;条状α相及针状马氏体α,相逐渐减少,转变为次生细长针状α组成网篮组织;1层时α相平均尺寸为2.24μm,经过5次堆积后,平均尺寸减小至1.27μm,且其晶体取向主要由0001和12-30晶向之间转向了0001与01-11晶向之间;最大极密度从30.14增大至46.8,经过5次热循环后,织构得到了强化。当堆积层数小于10层时,基材不同,基材与成型层之间的元素扩散是导致成型层组织与硬度区别的主要原因。FL_(TA3)、FL_(TC4)组织主要为条状α相和细长针状的α相组成的片层β转变组织,FL_(TA3)中α相尺寸更大,而FL_(TB5)存在大量的短小的针状马氏体α,相。显微硬度值变化趋势为FL_(TB5)大于FL_(TC4)大于FL_(TA3)。在堆积层数约5层内,FL_(TB5)的显微硬度可达到370HV左右,而FL_(TA3)、FL_(TC4)硬度则在300HV左右,堆积层数高于5层后,不同基材的成型层显微硬度差别减小,显微硬度值差为20HV左右。不同基材的成型层拉伸性能相差不大,拉伸强度为800MPa左右,延伸率均在20%以上,略低于退火态TC4基材。成型层断裂方式均为韧性断裂,与TC4基材断裂方式相同。基材-成型层界面的强度均比基材或成型层的强度高。成型层-TA3基材界面的断裂在TA3基材上的过渡区,断裂方式为准解理断裂;成型层-TB5基材界面的断裂在TB5基材上过渡区,断口方式为解理断裂;而成型层-TC4基材界面的断裂在成型层侧,断裂方式为韧性断裂。
[Abstract]:Titanium alloy has been widely used in the field of aerospace because of its property advantage. At the same time, the technology of adding material has obvious advantages in forming parts with complex structure, reducing processing procedure, shortening processing period, etc. It has a good application prospect in the field of advanced manufacturing technology. As a new technology, electron beam augmentation technology needs to be further explored in the aspects of forming structure and mechanical properties. In this paper, TA3,TB5,TC4 titanium alloy was used as the substrate, and the effect of wire feeding speed, wire feeding mode and beam strength on single channel multilayer forming was analyzed. The influence of substrate type on the microstructure, hardness and tensile strength of the molded parts and the tensile properties at the interface between the molding layer and the substrate were studied. The main process parameters affecting single-pass multilayer molding are wire feeding speed, deposition mode and beam intensity. When the wire feeding speed is Vs=20mm/s, 60 layers of single-wall samples can be obtained by combining the beam and the single layer with the appropriate reduction of the beam current. The forming layer of single wall specimen has obvious melting line pattern and laminar morphology, and its microstructure is a net structure composed of stripe 伪 phase and residual 尾, and the microhardness fluctuates between 260HV~300HV. The size of netted structure and the hardness of the molding layer changed periodically with the molding height 5mm as a unit. When the number of stacking layers is less than 5 layers, the forming layer structure is a coarse 尾 columnar crystal grown along the epitaxy, and the 伪 phase and the residual 尾 phase in the columnar crystal form a net like structure. The length and width of the columnar crystal increase with the increase of the number of the forming layers. The stripe 伪 phase and acicular martensite 伪 phase gradually decreased, and the secondary fine acicular 伪 formed a net basket tissue. The average size of 伪 phase is 2.24 渭 m in the first layer. After five stacking, the average size of 伪 phase decreases to 1.27 渭 m, and the orientation of 伪 phase is mainly shifted from 0001 and 12-30 to between 0001 and 01-11. The maximum polar density increased from 30.14 to 46.8, and the texture was strengthened after five thermal cycles. When the number of layers is less than 10 layers, the substrate is different, and the diffusion of elements between the substrate and the molding layer is the main reason for the difference between the microstructure and hardness of the molding layer.; FL_ (TA3), The structure of FL_ (TC4) is mainly composed of lamellar 尾 transition structure composed of stripe 伪 phase and slender needle-like 伪 phase. The size of 伪 phase in FL_ (TA3) is larger, while a large number of short acicular martensite 伪 and phase exist in FL_ (TB5). The change trend of microhardness is that FL_ (TB5) is larger than FL_ (TC4) than FL_ (TA3). The microhardness of FL_ (TB5) can reach about 370HV, while the hardness of FL_ (TA3) and FL_ (TC4) is about 300HV within about 5 layers. The microhardness difference is about 20HV. The tensile properties of different substrates have little difference. The tensile strength is about 800MPa, and the elongation is above 20%, which is slightly lower than that of annealed TC4 substrates. The fracture mode of forming layer is ductile fracture, which is the same as that of TC4 substrate. The strength of the interface between the substrate and the molding layer is higher than that of the substrate or the molding layer. The fracture of the interface between the forming layer and the TA3 substrate is in the transition zone on the TA3 substrate, and the fracture mode is quasi-cleavage fracture, while the fracture between the molding layer and the TB5 substrate is in the transition zone on the TB5 substrate, and the fracture mode is cleavage fracture. The fracture of the interface between the forming layer and the TC4 substrate is at the side of the forming layer, and the fracture mode is ductile fracture.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.23;TG661
本文编号：2295770
[Abstract]:Titanium alloy has been widely used in the field of aerospace because of its property advantage. At the same time, the technology of adding material has obvious advantages in forming parts with complex structure, reducing processing procedure, shortening processing period, etc. It has a good application prospect in the field of advanced manufacturing technology. As a new technology, electron beam augmentation technology needs to be further explored in the aspects of forming structure and mechanical properties. In this paper, TA3,TB5,TC4 titanium alloy was used as the substrate, and the effect of wire feeding speed, wire feeding mode and beam strength on single channel multilayer forming was analyzed. The influence of substrate type on the microstructure, hardness and tensile strength of the molded parts and the tensile properties at the interface between the molding layer and the substrate were studied. The main process parameters affecting single-pass multilayer molding are wire feeding speed, deposition mode and beam intensity. When the wire feeding speed is Vs=20mm/s, 60 layers of single-wall samples can be obtained by combining the beam and the single layer with the appropriate reduction of the beam current. The forming layer of single wall specimen has obvious melting line pattern and laminar morphology, and its microstructure is a net structure composed of stripe 伪 phase and residual 尾, and the microhardness fluctuates between 260HV~300HV. The size of netted structure and the hardness of the molding layer changed periodically with the molding height 5mm as a unit. When the number of stacking layers is less than 5 layers, the forming layer structure is a coarse 尾 columnar crystal grown along the epitaxy, and the 伪 phase and the residual 尾 phase in the columnar crystal form a net like structure. The length and width of the columnar crystal increase with the increase of the number of the forming layers. The stripe 伪 phase and acicular martensite 伪 phase gradually decreased, and the secondary fine acicular 伪 formed a net basket tissue. The average size of 伪 phase is 2.24 渭 m in the first layer. After five stacking, the average size of 伪 phase decreases to 1.27 渭 m, and the orientation of 伪 phase is mainly shifted from 0001 and 12-30 to between 0001 and 01-11. The maximum polar density increased from 30.14 to 46.8, and the texture was strengthened after five thermal cycles. When the number of layers is less than 10 layers, the substrate is different, and the diffusion of elements between the substrate and the molding layer is the main reason for the difference between the microstructure and hardness of the molding layer.; FL_ (TA3), The structure of FL_ (TC4) is mainly composed of lamellar 尾 transition structure composed of stripe 伪 phase and slender needle-like 伪 phase. The size of 伪 phase in FL_ (TA3) is larger, while a large number of short acicular martensite 伪 and phase exist in FL_ (TB5). The change trend of microhardness is that FL_ (TB5) is larger than FL_ (TC4) than FL_ (TA3). The microhardness of FL_ (TB5) can reach about 370HV, while the hardness of FL_ (TA3) and FL_ (TC4) is about 300HV within about 5 layers. The microhardness difference is about 20HV. The tensile properties of different substrates have little difference. The tensile strength is about 800MPa, and the elongation is above 20%, which is slightly lower than that of annealed TC4 substrates. The fracture mode of forming layer is ductile fracture, which is the same as that of TC4 substrate. The strength of the interface between the substrate and the molding layer is higher than that of the substrate or the molding layer. The fracture of the interface between the forming layer and the TA3 substrate is in the transition zone on the TA3 substrate, and the fracture mode is quasi-cleavage fracture, while the fracture between the molding layer and the TB5 substrate is in the transition zone on the TB5 substrate, and the fracture mode is cleavage fracture. The fracture of the interface between the forming layer and the TC4 substrate is at the side of the forming layer, and the fracture mode is ductile fracture.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.23;TG661
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