電子束增材制造鈦合金的組織特征與拉伸性能研究
發(fā)布時間：2018-10-26 12:46
【摘要】：鈦合金由于其性能優(yōu)勢,在航空航天領域得到廣泛的應用,同時增材制造技術在復雜結構零件成型、減少加工程序、縮短加工周期等方面具有明顯的優(yōu)勢,在先進制造技術領域有較好的應用前景。而電子束增材制造技術作為一種新型技術,在成型件組織、力學性能等方面還有待進一步探究。因此,本文以TA3、TB5、TC4鈦合金作為基材,對電子束增材制造鈦合金進行了研究,分析了送絲速度、送絲方式及束流強度對單道多層成型的影響;在此基礎上研究了單道多層組織及力學性能的變化規(guī)律,并著重分析了基材類型對成型件組織、硬度及拉伸強度的影響及成型層-基材界面處的拉伸性能變化規(guī)律。影響單道多層成型的工藝參數(shù)主要有送絲速度、沉積方式和束流強度。當送絲速度Vs=20mm/s時,適當減少束流并結合單、雙向沉積方式可得到60層單壁試樣。單壁試樣成型層上有明顯的熔凝線紋路及層帶形貌特征,其組織為條狀α相及殘余β組成的網(wǎng)籃狀組織,顯微硬度值在260HV~300HV之間波動,網(wǎng)籃狀組織尺寸及成型層硬度值均以成型高度5mm為一個單位呈現(xiàn)周期性變化。堆積層數(shù)低于5層時,成型層組織為沿外延生長的粗大β柱狀晶,柱狀晶內為α相及殘余β相組成網(wǎng)籃狀組織,隨著成型層數(shù)的增多,柱狀晶的長度和寬度均增大;條狀α相及針狀馬氏體α,相逐漸減少,轉變?yōu)榇紊氶L針狀α組成網(wǎng)籃組織;1層時α相平均尺寸為2.24μm,經(jīng)過5次堆積后,平均尺寸減小至1.27μm,且其晶體取向主要由0001和12-30晶向之間轉向了0001與01-11晶向之間;最大極密度從30.14增大至46.8,經(jīng)過5次熱循環(huán)后,織構得到了強化。當堆積層數(shù)小于10層時,基材不同,基材與成型層之間的元素擴散是導致成型層組織與硬度區(qū)別的主要原因。FL_(TA3)、FL_(TC4)組織主要為條狀α相和細長針狀的α相組成的片層β轉變組織,FL_(TA3)中α相尺寸更大,而FL_(TB5)存在大量的短小的針狀馬氏體α,相。顯微硬度值變化趨勢為FL_(TB5)大于FL_(TC4)大于FL_(TA3)。在堆積層數(shù)約5層內,FL_(TB5)的顯微硬度可達到370HV左右,而FL_(TA3)、FL_(TC4)硬度則在300HV左右,堆積層數(shù)高于5層后,不同基材的成型層顯微硬度差別減小,顯微硬度值差為20HV左右。不同基材的成型層拉伸性能相差不大,拉伸強度為800MPa左右,延伸率均在20%以上,略低于退火態(tài)TC4基材。成型層斷裂方式均為韌性斷裂,與TC4基材斷裂方式相同�；�-成型層界面的強度均比基材或成型層的強度高。成型層-TA3基材界面的斷裂在TA3基材上的過渡區(qū),斷裂方式為準解理斷裂;成型層-TB5基材界面的斷裂在TB5基材上過渡區(qū),斷口方式為解理斷裂;而成型層-TC4基材界面的斷裂在成型層側,斷裂方式為韌性斷裂。
[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 偽 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 偽 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 偽 phase and acicular martensite 偽 phase gradually decreased, and the secondary fine acicular 偽 formed a net basket tissue. The average size of 偽 phase is 2.24 渭 m in the first layer. After five stacking, the average size of 偽 phase decreases to 1.27 渭 m, and the orientation of 偽 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 偽 phase and slender needle-like 偽 phase. The size of 偽 phase in FL_ (TA3) is larger, while a large number of short acicular martensite 偽 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.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.23;TG661
本文編號：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 偽 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 偽 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 偽 phase and acicular martensite 偽 phase gradually decreased, and the secondary fine acicular 偽 formed a net basket tissue. The average size of 偽 phase is 2.24 渭 m in the first layer. After five stacking, the average size of 偽 phase decreases to 1.27 渭 m, and the orientation of 偽 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 偽 phase and slender needle-like 偽 phase. The size of 偽 phase in FL_ (TA3) is larger, while a large number of short acicular martensite 偽 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.
【學位授予單位】：南昌航空大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG146.23;TG661
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