For a long time,the deep penetration of laser beam welding(LBW)of ultra-thick titanium alloys used for super large-sized equipment has always been a significant challenge in engineering fields due to the dispersion of...For a long time,the deep penetration of laser beam welding(LBW)of ultra-thick titanium alloys used for super large-sized equipment has always been a significant challenge in engineering fields due to the dispersion of most laser beam energy in air.In this study,we designed the good matching of laser beam and welding parameters at a high power of 30 kW and a low ambient pressure of 0.3 Pa,and the deep weld penetration(95 mm)of Ti-6Al-4V alloy ultra-thick plates was first time achieved via vacuum LBW(VLBW).It was much larger than ever reported in titanium alloy VLBW joints.During VLBW,the plasma plume was gradually inhibited with the decrease in ambient pressures and basically disappeared below 101 Pa.The lower ambient pressure improved the stability of the molten pool,and enhanced the energy absorption inside the keyhole,thereby largely increasing the weld penetration.After VLBW,the contents of the impurity gas elements(N,H,and O)in the joint hardly changed.A relatively uniform welding temperature and cooling rate throughout the thickness resulted in a relatively homogeneous microstructure in the joint,leading to uniform hardness,strength,and toughness throughout the thickness.The secondaryα(α_(s))andαmartensite precipitated in the heat-affected zone and fusion zone,respectively.They increased theα_(s)/βand α/βinterfaces,resulting in their higher microhardness values than those in the base material(BM).In this case,the VLBW joint reached 987 MPa in strength,achieving equal strength welding to the BM.Furthermore,the impact energy(28 J)and fracture toughness(82.4 MPa m^(1/2))of the joint both could reach over 90%of the BM,achieving excellent strength-toughness matching.This study provides a new way for the high-property deep penetration welding of ultra-thick titanium alloys for large-sized components.展开更多
It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool...It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.展开更多
For a long time,the large loss of the strength and toughness of fusion welded joints for thick nearβtitanium alloys has largely hindered their engineering application,which results from the few precipitations of the ...For a long time,the large loss of the strength and toughness of fusion welded joints for thick nearβtitanium alloys has largely hindered their engineering application,which results from the few precipitations of the strengtheningαphase during welding cooling.In this study,double annealing treatment was designed for electron beam welded joints of 30-mm-thick nearβTi-5Al-5Mo-5V-1Cr-1Fe alloy,with the aim of regulating the proportion of multi-level lamellar microstructures and enhancing the joint properties.Among various annealing temperatures(first annealing at 750–880 ℃+second annealing at 580 ℃),the 750 ℃+580 ℃ annealed joint exhibited simultaneously enhanced strength and toughness,with the increase in tensile strength and impact energy from 844 MPa and 8.8 J for the as-welded joint to 1129 MPa and 14.5 J for annealed joint,respectively,which were superior to those of the joints of Ti5Al-5Mo-5V-1Cr-1Fe alloy as reported.The great increases in the strength and toughness were mainly attributed to the excellent proportion matching of formed multi-level lamellar microstructures(76.1%of primaryα(αp)lamellae and 7.9%of secondaryα(αs)lamellae),among which theαp phase andαs phase mainly affected the joint toughness and strength,respectively.The good coupling ofαp phase andαs phase improved the precipitation strengthening and the resistance to crack propagation.The modified strengthening mechanism models were proposed by introducing the thickness and proportion parameters of the precipitated phase.It was indicated that the theoretical calculation values were in good agreement with the experimental ones,and the solution strengthening and precipitation strengthening provided a large contribution(a sum of about 75%)to the yield strength of the annealed joints.This study provides a novel method via designing proper multi-level lamellar microstructures to simultaneously improve the strength and toughness of nearβtitanium alloy joints.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)+2 种基金the Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revitalization Talents Program(No.XLYC2403094)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.PTYQ2024YZ0009).
文摘For a long time,the deep penetration of laser beam welding(LBW)of ultra-thick titanium alloys used for super large-sized equipment has always been a significant challenge in engineering fields due to the dispersion of most laser beam energy in air.In this study,we designed the good matching of laser beam and welding parameters at a high power of 30 kW and a low ambient pressure of 0.3 Pa,and the deep weld penetration(95 mm)of Ti-6Al-4V alloy ultra-thick plates was first time achieved via vacuum LBW(VLBW).It was much larger than ever reported in titanium alloy VLBW joints.During VLBW,the plasma plume was gradually inhibited with the decrease in ambient pressures and basically disappeared below 101 Pa.The lower ambient pressure improved the stability of the molten pool,and enhanced the energy absorption inside the keyhole,thereby largely increasing the weld penetration.After VLBW,the contents of the impurity gas elements(N,H,and O)in the joint hardly changed.A relatively uniform welding temperature and cooling rate throughout the thickness resulted in a relatively homogeneous microstructure in the joint,leading to uniform hardness,strength,and toughness throughout the thickness.The secondaryα(α_(s))andαmartensite precipitated in the heat-affected zone and fusion zone,respectively.They increased theα_(s)/βand α/βinterfaces,resulting in their higher microhardness values than those in the base material(BM).In this case,the VLBW joint reached 987 MPa in strength,achieving equal strength welding to the BM.Furthermore,the impact energy(28 J)and fracture toughness(82.4 MPa m^(1/2))of the joint both could reach over 90%of the BM,achieving excellent strength-toughness matching.This study provides a new way for the high-property deep penetration welding of ultra-thick titanium alloys for large-sized components.
基金supported by the National Key Research and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)+2 种基金the Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revitalization Talents Program(No.XLYC2403094)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.PTYQ2024YZ0009).
文摘It is rather difficult for titanium alloy ultra-thick plates to achieve superior weld formation and excellent mechanical properties along the weld penetration direction due to the large fluctuations of the molten pool,largely limiting their engineering application.In this study,106-mm-thick Ti-6Al-4V ELI alloy plates were successfully butt welded via electron beam welding(EBW).The defect-free EBW joint with full penetration was obtained.The precipitated secondary α(α_(s))in heat affected zone(HAZ),αlamellae in fusion line(FL)and α′martensite in fusion zone(FZ)increased the α_(s)/β,α/β and α′/β interfaces,respectively,resulting in the higher microhardness and impact energy values(57 J in the HAZ,62 J in the FL and 51.9 J in the FZ)than those in the base material(BM).The impact energy of the joint in this study was higher than that for Ti-6Al-4V ELI alloy joints as reported,which was mainly attributed to the formation of the relatively thickerαphase and finer interlamellar spacing in this study,enhancing the resistance to crack propagation.Furthermore,the average fracture toughness(90.2 MPa m^(1/2))of the FZ was higher than that of the BM(74.2 MPa m^(1/2)).This study provides references for the welding application of titanium alloy ultra-thick plates in the manufacture of large-sized components.
基金supported by the National Key Re-search and Development Program of China(No.2023YFC2810700)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2021193)+2 种基金Liaoning Province Excellent Youth Foundation(No.2024JH3/10200021)the Liaoning Revital-ization Talents Program(No.XLYC2403094)the Scientific In-strument Developing Project of the Chinese Academy of Sciences(No.PTYQ2024YZ0009).
文摘For a long time,the large loss of the strength and toughness of fusion welded joints for thick nearβtitanium alloys has largely hindered their engineering application,which results from the few precipitations of the strengtheningαphase during welding cooling.In this study,double annealing treatment was designed for electron beam welded joints of 30-mm-thick nearβTi-5Al-5Mo-5V-1Cr-1Fe alloy,with the aim of regulating the proportion of multi-level lamellar microstructures and enhancing the joint properties.Among various annealing temperatures(first annealing at 750–880 ℃+second annealing at 580 ℃),the 750 ℃+580 ℃ annealed joint exhibited simultaneously enhanced strength and toughness,with the increase in tensile strength and impact energy from 844 MPa and 8.8 J for the as-welded joint to 1129 MPa and 14.5 J for annealed joint,respectively,which were superior to those of the joints of Ti5Al-5Mo-5V-1Cr-1Fe alloy as reported.The great increases in the strength and toughness were mainly attributed to the excellent proportion matching of formed multi-level lamellar microstructures(76.1%of primaryα(αp)lamellae and 7.9%of secondaryα(αs)lamellae),among which theαp phase andαs phase mainly affected the joint toughness and strength,respectively.The good coupling ofαp phase andαs phase improved the precipitation strengthening and the resistance to crack propagation.The modified strengthening mechanism models were proposed by introducing the thickness and proportion parameters of the precipitated phase.It was indicated that the theoretical calculation values were in good agreement with the experimental ones,and the solution strengthening and precipitation strengthening provided a large contribution(a sum of about 75%)to the yield strength of the annealed joints.This study provides a novel method via designing proper multi-level lamellar microstructures to simultaneously improve the strength and toughness of nearβtitanium alloy joints.
