Taking a Ti−5Al−5Mo−5V−1Cr−1Fe alloy as exemplary case,the fatigue crack growth sensitivity and fracture features with various tailoredαphase morphologies were thoroughly investigated using fatigue crack growth rate(...Taking a Ti−5Al−5Mo−5V−1Cr−1Fe alloy as exemplary case,the fatigue crack growth sensitivity and fracture features with various tailoredαphase morphologies were thoroughly investigated using fatigue crack growth rate(FCGR)test,optical microscopy(OM)and scanning electron microscopy(SEM).The tailored microstructures by heat treatments include the fine and coarse secondaryαphase,as well as the widmanstatten and basket weave features.The sample with coarse secondaryαphase exhibits better comprehensive properties of good crack propagation resistance(with long Paris regime ranging from 15 to 60 MPa·m1/2),high yield strength(1113 MPa)and ultimate strength(1150 MPa),and good elongation(11.6%).The good crack propagation resistance can be attributed to crack deflection,long secondary crack,and tortuous crack path induced by coarse secondaryαphase.展开更多
在Gleeble-1500热模拟机上对Ti-5Al-5Mo-5V-1Cr-1Fe合金进行高温热压缩实验,研究该合金在变形温度为750~900℃、应变速率为0.001~1 s 1条件下的流变应力行为。利用光学显微镜分析合金在不同变形条件下的组织演化规律。结果表明：合金的...在Gleeble-1500热模拟机上对Ti-5Al-5Mo-5V-1Cr-1Fe合金进行高温热压缩实验,研究该合金在变形温度为750~900℃、应变速率为0.001~1 s 1条件下的流变应力行为。利用光学显微镜分析合金在不同变形条件下的组织演化规律。结果表明：合金的流变应力随着应变速率的增大和变形温度的降低而增大;流变应力随着应变的增加而增大,出现峰值后逐渐趋于平稳;变形过程中的流变应力可用Arrhenius双曲正弦本构关系来描述,平均变形激活能为454.2 kJ/mol;各种变形条件均可细化原始晶粒尺寸。随着温度的升高和应变速率的降低,合金的主要软化机制由动态回复逐渐变为动态再结晶;在（α＋β）相区变形（750~850℃）时,α相对β晶粒的动态再结晶的发生起到阻碍作用。展开更多
In this work,a near-beta Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy was fabricated by selective laser melting(SLM),and the microstructure evolution together with the mechanical properties was studied.The as-fabricated alloy...In this work,a near-beta Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy was fabricated by selective laser melting(SLM),and the microstructure evolution together with the mechanical properties was studied.The as-fabricated alloy showed columnarβgrains spreading over multiple layers and paralleling to the building direction.The distinct microstructure of as-fabricated alloy was composed of near-β(more than 98.1%)with a submicron cellular structure.Different SLM processing parameters such as hatch spacing could affect the microstructure of as-fabricated alloy,which could thus further significantly affect the mechanical properties of as-fabricated alloy.In addition,the as-fabricated alloy with the distinct microstructure exhibits yield strength of 818 MPa combined with elongation of more than 19%,which shows that SLM is a potential technology for manufacturing near-beta titanium components.展开更多
Hot compression behavior of Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe alloy with an equiaxed（α＋β） starting microstructure was investigated by isothermal compression test and optical microscopy. Based on the true strain-stress d...Hot compression behavior of Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe alloy with an equiaxed（α＋β） starting microstructure was investigated by isothermal compression test and optical microscopy. Based on the true strain-stress data with temperature correction, constitutive models with a high accuracy were developed and processing maps were established. Strain inhomogeneity at different locations in the compressed sample is reduced by raising temperature, leading to a uniform distribution of α phases. For the temperature range of 800-840 ℃ with a strain rate of 10 s^-1, the transformed volume fraction of α phase increases and the average grain size of α phase decreases slightly with increasing the temperature, indicating co-existence of dynamic recovery and dynamic recrystallization. Flow localization and faint β grain boundaries are observed at the strain rate of 10 s^-1 in the temperature range of 860-900 ℃. The processing map analysis shows that hot working of Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe alloy should be conducted with the strain rate lower than 0.01 s^-1 to extend its workability.展开更多
The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue cr...The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.展开更多
The microstructural evolution, mechanical properties and fracture mechanism of a Ti.5Al.5Mo.5V.3Cr.1Zr (Ti-55531) alloy after solution (760.820℃) plus aging (580.640℃) treatments were investigated. The results show ...The microstructural evolution, mechanical properties and fracture mechanism of a Ti.5Al.5Mo.5V.3Cr.1Zr (Ti-55531) alloy after solution (760.820℃) plus aging (580.640℃) treatments were investigated. The results show that the volume fraction of the primary α(αp) phase decreases with the increase of solution temperature, and the length of the secondary α phase (αs) decreases while its width increases with the increase of aging temperature. Yield and tensile strengths decrease with the increase of solution temperature, while increase with the increase of aging temperature. A good balance of tensile strength and ductility of the alloy is obtained under solution of 800℃ for 2 h plus aging of 640℃ for 8 h, in which the tensile strength is 1434 MPa and the elongation is 7.7%. The coarsening αs phase makes crack propagation paths deflected and tortuous, which increases the crack propagation resistance and improves the ductility and fracture toughness.展开更多
Split Hopkinson pressure bar test system was used to investigate the plastic deformation behavior and dynamic response character of a-type Ti–5Al–2.5Sn ELI and near a-type Ti–8Al–1Mo–1V titanium alloy when subjec...Split Hopkinson pressure bar test system was used to investigate the plastic deformation behavior and dynamic response character of a-type Ti–5Al–2.5Sn ELI and near a-type Ti–8Al–1Mo–1V titanium alloy when subjected to dynamic loading. In the present work, stress–strain curves at strain rate from 1.5 9 103to 5.0 9 103s-1were analyzed, and optical microscope（OM） was used to reveal adiabatic shearing behavior of recovered samples. Results show that both the two alloys manifest significant strain hardening effects. Critical damage strain rate of the two alloys is about 4.3 9 103s-1, under which the impact absorbs energy of Ti–5Al–2.5Sn ELI and Ti–8Al–1Mo–1V are 560 and 470 MJ m-3, respectively. Both of them fracture along the maximum shearing strength orientation, an angle of 45° to the compression axis. No adiabatic shear band（ASB） is found in Ti–5Al–2.5Sn ELI alloy, whereas several ASBs with different widths exist without regular direction in Ti–8Al–1Mo–1V alloy.展开更多
基金Project(U1867201)supported by the National Natural Science Foundation of ChinaProject supported by State Key Laboratory of Powder Metallurgy,Central South University,China。
文摘Taking a Ti−5Al−5Mo−5V−1Cr−1Fe alloy as exemplary case,the fatigue crack growth sensitivity and fracture features with various tailoredαphase morphologies were thoroughly investigated using fatigue crack growth rate(FCGR)test,optical microscopy(OM)and scanning electron microscopy(SEM).The tailored microstructures by heat treatments include the fine and coarse secondaryαphase,as well as the widmanstatten and basket weave features.The sample with coarse secondaryαphase exhibits better comprehensive properties of good crack propagation resistance(with long Paris regime ranging from 15 to 60 MPa·m1/2),high yield strength(1113 MPa)and ultimate strength(1150 MPa),and good elongation(11.6%).The good crack propagation resistance can be attributed to crack deflection,long secondary crack,and tortuous crack path induced by coarse secondaryαphase.
文摘在Gleeble-1500热模拟机上对Ti-5Al-5Mo-5V-1Cr-1Fe合金进行高温热压缩实验,研究该合金在变形温度为750~900℃、应变速率为0.001~1 s 1条件下的流变应力行为。利用光学显微镜分析合金在不同变形条件下的组织演化规律。结果表明：合金的流变应力随着应变速率的增大和变形温度的降低而增大;流变应力随着应变的增加而增大,出现峰值后逐渐趋于平稳;变形过程中的流变应力可用Arrhenius双曲正弦本构关系来描述,平均变形激活能为454.2 kJ/mol;各种变形条件均可细化原始晶粒尺寸。随着温度的升高和应变速率的降低,合金的主要软化机制由动态回复逐渐变为动态再结晶;在（α＋β）相区变形（750~850℃）时,α相对β晶粒的动态再结晶的发生起到阻碍作用。
基金Project(2019B010943001)supported by Key-area Research and Development Program of Guangdong Province,ChinaProject(2020)supported by the Fund of State Key Laboratory of Powder Metallurgy,Central South University,China。
文摘In this work,a near-beta Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy was fabricated by selective laser melting(SLM),and the microstructure evolution together with the mechanical properties was studied.The as-fabricated alloy showed columnarβgrains spreading over multiple layers and paralleling to the building direction.The distinct microstructure of as-fabricated alloy was composed of near-β(more than 98.1%)with a submicron cellular structure.Different SLM processing parameters such as hatch spacing could affect the microstructure of as-fabricated alloy,which could thus further significantly affect the mechanical properties of as-fabricated alloy.In addition,the as-fabricated alloy with the distinct microstructure exhibits yield strength of 818 MPa combined with elongation of more than 19%,which shows that SLM is a potential technology for manufacturing near-beta titanium components.
基金Project(BS2013CL034)supported by the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province,ChinaProject(51401115)supported by the National Natural Science Foundation of ChinaProject(GN2013001)supported by Independent Innovation Foundation of Shandong University,China
文摘Hot compression behavior of Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe alloy with an equiaxed（α＋β） starting microstructure was investigated by isothermal compression test and optical microscopy. Based on the true strain-stress data with temperature correction, constitutive models with a high accuracy were developed and processing maps were established. Strain inhomogeneity at different locations in the compressed sample is reduced by raising temperature, leading to a uniform distribution of α phases. For the temperature range of 800-840 ℃ with a strain rate of 10 s^-1, the transformed volume fraction of α phase increases and the average grain size of α phase decreases slightly with increasing the temperature, indicating co-existence of dynamic recovery and dynamic recrystallization. Flow localization and faint β grain boundaries are observed at the strain rate of 10 s^-1 in the temperature range of 860-900 ℃. The processing map analysis shows that hot working of Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe alloy should be conducted with the strain rate lower than 0.01 s^-1 to extend its workability.
文摘The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.
基金Project(SKLSP201853) supported by the Fund of the State Key Laboratory of Solidification Processing in NWPU,ChinaProject(51625505) supported by the National Science Fund for Distinguished Young Scholars of China+1 种基金Project(U1537203) supported by the Key Program Project of the Joint Fund of Astronomy and National Natural Science Foundation of ChinaProject(KYQD1801) supported by the Scientific Research Foundation of Tianjin University of Technology and Education,China
文摘The microstructural evolution, mechanical properties and fracture mechanism of a Ti.5Al.5Mo.5V.3Cr.1Zr (Ti-55531) alloy after solution (760.820℃) plus aging (580.640℃) treatments were investigated. The results show that the volume fraction of the primary α(αp) phase decreases with the increase of solution temperature, and the length of the secondary α phase (αs) decreases while its width increases with the increase of aging temperature. Yield and tensile strengths decrease with the increase of solution temperature, while increase with the increase of aging temperature. A good balance of tensile strength and ductility of the alloy is obtained under solution of 800℃ for 2 h plus aging of 640℃ for 8 h, in which the tensile strength is 1434 MPa and the elongation is 7.7%. The coarsening αs phase makes crack propagation paths deflected and tortuous, which increases the crack propagation resistance and improves the ductility and fracture toughness.
基金financially supported by the Ministry of Science and Technology of China (No. 2012DFG51540)
文摘Split Hopkinson pressure bar test system was used to investigate the plastic deformation behavior and dynamic response character of a-type Ti–5Al–2.5Sn ELI and near a-type Ti–8Al–1Mo–1V titanium alloy when subjected to dynamic loading. In the present work, stress–strain curves at strain rate from 1.5 9 103to 5.0 9 103s-1were analyzed, and optical microscope（OM） was used to reveal adiabatic shearing behavior of recovered samples. Results show that both the two alloys manifest significant strain hardening effects. Critical damage strain rate of the two alloys is about 4.3 9 103s-1, under which the impact absorbs energy of Ti–5Al–2.5Sn ELI and Ti–8Al–1Mo–1V are 560 and 470 MJ m-3, respectively. Both of them fracture along the maximum shearing strength orientation, an angle of 45° to the compression axis. No adiabatic shear band（ASB） is found in Ti–5Al–2.5Sn ELI alloy, whereas several ASBs with different widths exist without regular direction in Ti–8Al–1Mo–1V alloy.
