High Nb-TiAl (Ti-44Al-8Nb-0.2W-0.2B-0.5Y,at.%) ingot was fabricated by vacuum arc remelting (VAR).The as-cast ingot was hot-isostatic pressed (HIP) and homogenizing annealing processed.The influence of heat treatment ...High Nb-TiAl (Ti-44Al-8Nb-0.2W-0.2B-0.5Y,at.%) ingot was fabricated by vacuum arc remelting (VAR).The as-cast ingot was hot-isostatic pressed (HIP) and homogenizing annealing processed.The influence of heat treatment temperature and thermomechanical processing on the microstructure and tensile property of the alloy was investigated by X-ray diffractometry (XRD),scanning electron microscopy (SEM) and tensile tests.It was found that the high Nb-TiAl alloy after HIP and annealing was mainly composed of coarse α2/γ lamellae,β/B2 phase and γ phase and the solidification path of this alloy was:L→L+β→β→α+β→α→α+β+γ→α2+β+γ.The water quenching results showed that the alloy was in α single phase region at 1,340 °C.After heating at 1,340 °C for 30 min followed by furnace cooling,the alloy showed a full lamellar microstructure and its ultimate tensile strength was about 538 MPa,with an elongation of 0.3% at room temperature.Free-crack forged pancakes with fine-grained fully lamellar structure (FFLS) were obtained with an initial deformation temperature of 1,340 °C and the ultimate tensile strength of forged alloy was about 820 MPa,with an elongation of 0.9% at room temperature,which was much higher than that of alloy after HIP and annealing because of microstructural refinement.展开更多
A novel nonlinear gray transform method is proposed to enhance the contrast of a typhoon cloud image.Generally,the typhoon cloud image obtained by a satellite cannot be directly used to make an accurate prediction of ...A novel nonlinear gray transform method is proposed to enhance the contrast of a typhoon cloud image.Generally,the typhoon cloud image obtained by a satellite cannot be directly used to make an accurate prediction of the typhoon＇s center or intensity because the contrast of the received typhoon cloud image may be bad.Our aim is to extrude the typhoon＇s eye in the typhoon cloud image.A normalized arc-tangent transformation operation is designed to enhance global contrast of the typhoon cloud image.Differential evolution algorithm is used to choose the optimal nonlinear transform parameter.Finally,geodesic activity contour model is used to extract the typhoon＇s eye to verify the performance of the proposed method.Experimental results show that the proposed method can efficiently enhance the global contrast of the typhoon cloud image while greatly extruding the typhoon＇s eye.展开更多
The microstructure and cellular transition characteristics of an intermetallic Ti-42Al-3Nb-1Mo-0.1B (at.%) alloy were investigated.The as-cast microstructure of the alloy is mainly composed of (α2+γ) lamellar struct...The microstructure and cellular transition characteristics of an intermetallic Ti-42Al-3Nb-1Mo-0.1B (at.%) alloy were investigated.The as-cast microstructure of the alloy is mainly composed of (α2+γ) lamellar structure and (β+γ) mixture structure,which distributes along the boundaries of the lamellar colonies.In order to study the phase transformation of lamellar structure at aging temperature,a two-step heat treatment was carried out.After the first step of annealing treatment at 1,260 °C,the microstructure with relatively finer lamellar space and (γ+β/B2) mixture structure is obtained.Aging treatment,as the second heat treatment step,has significant influence on the microstructure,attributing to a cellular reaction of α2+γ→γ+β.With the increase of aging temperature,the (α2+γ) lamellar structure continues to dissolve,whereas the contents of both the equiaxed γ and β/B2 grains continuously increase.Besides,the orientation of lamellae α2,equiaxed γ and equiaxed β/B2 in the cellular transition region follows a specific relationship of {0-11}β<1-11>β//{0001}α2<2-1-10>α2//{1-11}γ<-101>γ.展开更多
In this study, a new near-beta titanium alloy, Ti- 4Al-1 Sn-2Zr-5Mo-8V-2.5Cr, was prepared by induction skull melting (ISM) and multidirectional forging. The effect of aging heat treat me rn on microstructure and ten ...In this study, a new near-beta titanium alloy, Ti- 4Al-1 Sn-2Zr-5Mo-8V-2.5Cr, was prepared by induction skull melting (ISM) and multidirectional forging. The effect of aging heat treat me rn on microstructure and ten sile properties of the alloy after solution treatment in the twophase (α+β) region was investigated. The microstructure results show that the globular primary ot phase (cxp) and the needle-like secondary y. phase (ots) are precipitated in the P matrix. The size of ots increases with the increase in aging temperature, while the con tent of ots goes up to a peak value and then decreases. The tensile testing results show that the strength increases first and then decreases with the in crease in temperature. The variation of ductility presents the opposite way compared with the trend of strength level. When aged at 500℃, the alloy exhibits an excellebalance of tensile strength (1529 MPa) and elongation (9.22%). And the relative mechanism of sirengthening and toughening was analyzed and discussed.展开更多
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(Nos.52171122,52071228,51904205,51901151)the Natural Science Foundation of Shanxi Province,China(No.20210302124077)+2 种基金the Central Government Guides the Special Fund Projects of Local Scientific and Technological Development,China(No.YDZJSX2021A016)the Natural Science Foundation of Ningxia,China(No.2022AAC02077)the Key Research and Development Program of Shanxi Province,China(Nos.201903D421084,201903D121056).
基金the financial supports from the Key Research and Development Program of Shanxi Province,China(Nos.201903D421084,201903D121056)the National Natural Science Foundation of China(Nos.52171122,52071228,51901151)。
基金the National Natural Science Foundation of China(Project Nos.:51971074,51471056)the State Key Laboratory for Advanced Metal and Materials Foundation(Project No.:2013-ZD06)the National Basic Research Program of China(Project No.:2011CB605502)。
文摘High Nb-TiAl (Ti-44Al-8Nb-0.2W-0.2B-0.5Y,at.%) ingot was fabricated by vacuum arc remelting (VAR).The as-cast ingot was hot-isostatic pressed (HIP) and homogenizing annealing processed.The influence of heat treatment temperature and thermomechanical processing on the microstructure and tensile property of the alloy was investigated by X-ray diffractometry (XRD),scanning electron microscopy (SEM) and tensile tests.It was found that the high Nb-TiAl alloy after HIP and annealing was mainly composed of coarse α2/γ lamellae,β/B2 phase and γ phase and the solidification path of this alloy was:L→L+β→β→α+β→α→α+β+γ→α2+β+γ.The water quenching results showed that the alloy was in α single phase region at 1,340 °C.After heating at 1,340 °C for 30 min followed by furnace cooling,the alloy showed a full lamellar microstructure and its ultimate tensile strength was about 538 MPa,with an elongation of 0.3% at room temperature.Free-crack forged pancakes with fine-grained fully lamellar structure (FFLS) were obtained with an initial deformation temperature of 1,340 °C and the ultimate tensile strength of forged alloy was about 820 MPa,with an elongation of 0.9% at room temperature,which was much higher than that of alloy after HIP and annealing because of microstructural refinement.
基金supported by National Natural Science Foundation of China (No. 40805048,No. 11026226)Typhoon Research Foundation of Shanghai Typhoon Institute/China Meteorological Administration (No. 2008ST01)+1 种基金Research Foundation of State Key Laboratory of Remote Sensing Science,Jointly sponsored by the Instituteof Remote Sensing Applications of Chinese Academy of Sciences and Beijing Normal University (No. 2009KFJJ013)Research Foundation of State Key Laboratory of Severe Weather/Chinese Academy of Meteorological Sciences (No. 2008LASW-B03)
文摘A novel nonlinear gray transform method is proposed to enhance the contrast of a typhoon cloud image.Generally,the typhoon cloud image obtained by a satellite cannot be directly used to make an accurate prediction of the typhoon＇s center or intensity because the contrast of the received typhoon cloud image may be bad.Our aim is to extrude the typhoon＇s eye in the typhoon cloud image.A normalized arc-tangent transformation operation is designed to enhance global contrast of the typhoon cloud image.Differential evolution algorithm is used to choose the optimal nonlinear transform parameter.Finally,geodesic activity contour model is used to extract the typhoon＇s eye to verify the performance of the proposed method.Experimental results show that the proposed method can efficiently enhance the global contrast of the typhoon cloud image while greatly extruding the typhoon＇s eye.
基金the National Natural Science Foundation of China(Grant Nos.:52071228,51704174,51801112)the Natural Science Foundation of Shanxi Province(Grant Nos.:201903D121056 and 201903D421084)the Shandong Province Key Research and Development Program(Grant No.:2019GGX102045)。
文摘The microstructure and cellular transition characteristics of an intermetallic Ti-42Al-3Nb-1Mo-0.1B (at.%) alloy were investigated.The as-cast microstructure of the alloy is mainly composed of (α2+γ) lamellar structure and (β+γ) mixture structure,which distributes along the boundaries of the lamellar colonies.In order to study the phase transformation of lamellar structure at aging temperature,a two-step heat treatment was carried out.After the first step of annealing treatment at 1,260 °C,the microstructure with relatively finer lamellar space and (γ+β/B2) mixture structure is obtained.Aging treatment,as the second heat treatment step,has significant influence on the microstructure,attributing to a cellular reaction of α2+γ→γ+β.With the increase of aging temperature,the (α2+γ) lamellar structure continues to dissolve,whereas the contents of both the equiaxed γ and β/B2 grains continuously increase.Besides,the orientation of lamellae α2,equiaxed γ and equiaxed β/B2 in the cellular transition region follows a specific relationship of {0-11}β<1-11>β//{0001}α2<2-1-10>α2//{1-11}γ<-101>γ.
基金financially supported by the National Natural Science Foundation of China (Nos. 51504163, 51604191 and 51601099)
文摘In this study, a new near-beta titanium alloy, Ti- 4Al-1 Sn-2Zr-5Mo-8V-2.5Cr, was prepared by induction skull melting (ISM) and multidirectional forging. The effect of aging heat treat me rn on microstructure and ten sile properties of the alloy after solution treatment in the twophase (α+β) region was investigated. The microstructure results show that the globular primary ot phase (cxp) and the needle-like secondary y. phase (ots) are precipitated in the P matrix. The size of ots increases with the increase in aging temperature, while the con tent of ots goes up to a peak value and then decreases. The tensile testing results show that the strength increases first and then decreases with the in crease in temperature. The variation of ductility presents the opposite way compared with the trend of strength level. When aged at 500℃, the alloy exhibits an excellebalance of tensile strength (1529 MPa) and elongation (9.22%). And the relative mechanism of sirengthening and toughening was analyzed and discussed.
