A Zr-rich phase,Ni_5Zr,with low melting point has been fouhd in an Ni_3Al alloy doped with Zr(1.2at.-%).It will cause the incipient melt of the alloy after being homogenized at 1300℃. This makes it difficult to homog...A Zr-rich phase,Ni_5Zr,with low melting point has been fouhd in an Ni_3Al alloy doped with Zr(1.2at.-%).It will cause the incipient melt of the alloy after being homogenized at 1300℃. This makes it difficult to homogenize the coarse casting structures completely and limits the further improvement of properties of the Ni_3Al alloy.展开更多
An additive of Y to Ni_3Al based alloy may form a phase YNi_5 which increases in amount with the increase of Y content.It was found that the YNi_5 phase in Ni_3Al alloy could remarkably make its grains finer and its g...An additive of Y to Ni_3Al based alloy may form a phase YNi_5 which increases in amount with the increase of Y content.It was found that the YNi_5 phase in Ni_3Al alloy could remarkably make its grains finer and its grain boundaries more crooked other than straight.If the Y con- tent≥0.1 wt-%,it occurs as solid solution state and is favorable to high temperature compressive properties and oxidation resistance of the alloy.While Y≥0.3 wt-%,the forma- tion of YNi_5 is predominant in the shape of irregular strips inside Ni_3Al grains and along their grain boundaries.This seems to be quite harmful to high temperature strength,ductility and oxidation resistance of the alloy.展开更多
In consideration of the envelopment of γ dendrites by the Hf-rich melts at the late period of solidification of the cast Ni-base superalloys containing Hf,a heat of brazing filler alloy composed of Ni-18.6Co-4.5Cr-4....In consideration of the envelopment of γ dendrites by the Hf-rich melts at the late period of solidification of the cast Ni-base superalloys containing Hf,a heat of brazing filler alloy composed of Ni-18.6Co-4.5Cr-4.7 W-25.6Hf(wt-%)was prepared.This alloy is hypereutectic.γ phase is the leading phase in eutectic γ+Ni_5Hf and γ bars are surrounded by Ni_5Hf phase.At the section perpendicular or parallel to the γ growing direction,the eutectic morphology is cellular or laminar respectively.The content of Ni_5Hf in the alloy is 68.7v.-%. The compositions of primary and eutectic Ni_5Hf are very similar.Ni,Co and Hf are the main elements and solubility of Cr and W in Ni_5Hf is very low.This alloy is an ideal brazing filler suitable to the directional or single crystal superalloy,and the elements are beneficial to superalloys properties.This filler alloy is of low melting point and of good fluidity.After braz- ing at 1240℃,5 min+1190℃,I h in 10^(-3) Pa vacuum,the microstructure of bond is the same as that of Hf-bearing superalloy.No Si and B contamination is involved.展开更多
Based on X-ray diffraction, microscopic and magnetic analysis, the structure and magnetic properties of Co77Zr18W5 melt-spun ribbons were studied in this paper. A new element to stabilize the metastable Co5Zr phase wa...Based on X-ray diffraction, microscopic and magnetic analysis, the structure and magnetic properties of Co77Zr18W5 melt-spun ribbons were studied in this paper. A new element to stabilize the metastable Co5Zr phase was found and the coercivity observed in Co-Zr alloys can be obviously enhanced by proper tungsten substitution. The Curie temperature of Co77Zr18W5 ribbons is 475℃ which suggests that W doped Co-Zr alloys may become an attractive candidate perma- nent magnets for practical applications in high temperature. Annealing of the Co77Zr18W5 ribbons results in a decrease of the coercivity which confirmed that the hard magnetic phase is Co5Zr phase in 77Zr18W5 melt-spun ribbons.展开更多
Impact, tensile, and fatigue tests were performed in In783 alloy serving 4000, 23,000 and 48,000 h. The microstructure was then analysed by optical microscopy(OM), scanning electron microscopy(SEM), and transmission e...Impact, tensile, and fatigue tests were performed in In783 alloy serving 4000, 23,000 and 48,000 h. The microstructure was then analysed by optical microscopy(OM), scanning electron microscopy(SEM), and transmission electron microscopy(TEM) to probe the relationship between microstructure and properties. The results show that a new Ni_(5)Al_(3) phase is found, which grows gradually in β phase with serving time increasing,destroying the martensitic structure of the β phase, and degenerating the toughness of the β phase(approximately13.88% reduction). Therefore, the degradation of the βphase results in a sharp dropping of the resistance to stress accelerated grain boundary oxygen(SAGBO) during serving;thus, the intergranular fracture morphology degree increases with duration of service(almost 40% increase from the fractured surface). In addition, the strength of alloy will be gradually enhanced when the γ'phase becomes relatively bulky with serving time increasing due to considerable distortion of the dislocations as a result of the spacing of individual particles, in which any movement of the dislocation will have to overcome a larger number of obstacles per unit length.展开更多
As reported in our previous works, a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures. In Mg-7Gd-5Y-1...As reported in our previous works, a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures. In Mg-7Gd-5Y-1Nd-0.5Zr alloy, the β pre- cipitate phase was assumed to he one of the main strengthening phases in peak-aged samples. This study aimed to determine the crys- tal structure and orientation relationship of the β precipitate phase in Mg-7Gd-5Y-INd-0.5Zr alloy using transmission electron mi- croscopy and high-resolution electron microscopy. The results indicated that the β precipitate had a face-centered cubic structure with a lattice parameter of a=2.22 nm. The orientation relationship between the β precipitate phase and the ct-Mg matrix was （i-12）β（1-100）α, [110]β[0001 ]α. Theβ plates formed on prismatic planes could play an important role in alloy strengthening by proving effective barriers to gliding dislocations. A single β plate often contained several domains of （1 11）β twin-related variants. A composition of Mgs（Y0.4Gdo.4Nd0.2） was suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.展开更多
The minor precipitations caused by B and Zr which are the normal constituents of U720 Li alloy have been studied by analyzing the solidification process and the composition evolution. The present study aims to supply ...The minor precipitations caused by B and Zr which are the normal constituents of U720 Li alloy have been studied by analyzing the solidification process and the composition evolution. The present study aims to supply the elementary information about the existing form of B and Zr in the as-cast microstructure, which is helpful for the subsequent processing, such as homogenization treatment. The M_3B_2 and Ni_5Zr phases were observed in the U720 Li alloy in as-cast state, which were usually accompanying with each other together with g-Ni_3 Ti phase at the edge of eutectic（γ＋γ＇）. Combining the DTA analysis and heating and quenching tests, the solidification sequence was determined to be the following： c matrix, eutectic（γ＋γ＇）, g-Ni_3Ti, M_3B_2 and Ni_5Zr. The in situ composition analysis by EDS and EPMA revealed that the precipitation and microstructure were governed by the composition evolution in the liquids. The solidification of c matrix increased the Ti concentration in the residual liquids and resulted in the eutectic（γ＋γ＇） formation; the（γ＋γ＇） formation increased the Ti/Al radio in the liquids and the g-Ni_3Ti was formed in front of the eutectic（γ＋γ＇）; the g-Ni_3Ti precipitation consumed up Al and Ti and increased the concentration of B, Mo and Cr, and M_3B_2 boride is formed;the previous precipitation of the phases consumed up most of the elements other than Ni and Zr, and Ni_5Zr is formed finally. The melting points are in the ranges of 1130–1140 °C for Ni_5Zr phase, 1180–1190 °C for M_3B_2 boride and1190–1200 °C for g-Ni_3Ti phase.展开更多
La–Mg–Ni-based hydrogen storage alloys have excellent hydrogen storage properties.This work reports the hydrogen storage performance of a series of A_(2)B_(7)-type La_(0.96)Mg_(0.04)N_(i3.34)Al_(0.13)alloy and La_(0...La–Mg–Ni-based hydrogen storage alloys have excellent hydrogen storage properties.This work reports the hydrogen storage performance of a series of A_(2)B_(7)-type La_(0.96)Mg_(0.04)N_(i3.34)Al_(0.13)alloy and La_(0.96-x)Y_(x)Mg_(0.04)Ni_(3.47–0.6x)Al_(0.6x)(x=0,0.22,0.33,0.44)alloys,and explores the effect of Y and Al element combined substitution on the microstructure and hydrogen storage performance of A_(2)B_(7)-type La–Mg–Ni-based alloys.The alloys are composed of Ce_(2)Ni_(7)phase and LaNi_(5)phase.With the increase of x,the cell volume of Ce_(2)Ni_(7)phase decreases,while that of LaNi_(5)phase increases,indicating that Y atom mainly enters Ce_(2)Ni_(7)phase and Al atom mainly enters LaNi_(5)phase.An appropriate amount of co-substitution increases the hydrogen storage capacity and reduces the hydrogen absorption/desorption plateau pressure hysteresis of the alloy.When x=0.44,the hydrogen storage capacity of the alloy is 1.449 wt%,and the hysteresis coefficient is 0.302.The cell volume of Ce_(2)Ni_(7)phase and LaNi_(5)phase expands to different degrees after 20 absorption/desorption cycles.With the increase of x,the volume expansion rate decreases,and the cycle capacity retention rate also gradually decreases.This is related to the amorphization of Ce_(2)Ni_(7)phase.When x=0.22,the capacity retention rate of the alloy is 91.4%.展开更多
文摘A Zr-rich phase,Ni_5Zr,with low melting point has been fouhd in an Ni_3Al alloy doped with Zr(1.2at.-%).It will cause the incipient melt of the alloy after being homogenized at 1300℃. This makes it difficult to homogenize the coarse casting structures completely and limits the further improvement of properties of the Ni_3Al alloy.
文摘An additive of Y to Ni_3Al based alloy may form a phase YNi_5 which increases in amount with the increase of Y content.It was found that the YNi_5 phase in Ni_3Al alloy could remarkably make its grains finer and its grain boundaries more crooked other than straight.If the Y con- tent≥0.1 wt-%,it occurs as solid solution state and is favorable to high temperature compressive properties and oxidation resistance of the alloy.While Y≥0.3 wt-%,the forma- tion of YNi_5 is predominant in the shape of irregular strips inside Ni_3Al grains and along their grain boundaries.This seems to be quite harmful to high temperature strength,ductility and oxidation resistance of the alloy.
文摘In consideration of the envelopment of γ dendrites by the Hf-rich melts at the late period of solidification of the cast Ni-base superalloys containing Hf,a heat of brazing filler alloy composed of Ni-18.6Co-4.5Cr-4.7 W-25.6Hf(wt-%)was prepared.This alloy is hypereutectic.γ phase is the leading phase in eutectic γ+Ni_5Hf and γ bars are surrounded by Ni_5Hf phase.At the section perpendicular or parallel to the γ growing direction,the eutectic morphology is cellular or laminar respectively.The content of Ni_5Hf in the alloy is 68.7v.-%. The compositions of primary and eutectic Ni_5Hf are very similar.Ni,Co and Hf are the main elements and solubility of Cr and W in Ni_5Hf is very low.This alloy is an ideal brazing filler suitable to the directional or single crystal superalloy,and the elements are beneficial to superalloys properties.This filler alloy is of low melting point and of good fluidity.After braz- ing at 1240℃,5 min+1190℃,I h in 10^(-3) Pa vacuum,the microstructure of bond is the same as that of Hf-bearing superalloy.No Si and B contamination is involved.
文摘Based on X-ray diffraction, microscopic and magnetic analysis, the structure and magnetic properties of Co77Zr18W5 melt-spun ribbons were studied in this paper. A new element to stabilize the metastable Co5Zr phase was found and the coercivity observed in Co-Zr alloys can be obviously enhanced by proper tungsten substitution. The Curie temperature of Co77Zr18W5 ribbons is 475℃ which suggests that W doped Co-Zr alloys may become an attractive candidate perma- nent magnets for practical applications in high temperature. Annealing of the Co77Zr18W5 ribbons results in a decrease of the coercivity which confirmed that the hard magnetic phase is Co5Zr phase in 77Zr18W5 melt-spun ribbons.
基金financially supported by the National Key R&D Program of China (2016YFC081902)the Shenhua Guohua (Beijing) Electric Power Research Institute Co.,Ltd。
文摘Impact, tensile, and fatigue tests were performed in In783 alloy serving 4000, 23,000 and 48,000 h. The microstructure was then analysed by optical microscopy(OM), scanning electron microscopy(SEM), and transmission electron microscopy(TEM) to probe the relationship between microstructure and properties. The results show that a new Ni_(5)Al_(3) phase is found, which grows gradually in β phase with serving time increasing,destroying the martensitic structure of the β phase, and degenerating the toughness of the β phase(approximately13.88% reduction). Therefore, the degradation of the βphase results in a sharp dropping of the resistance to stress accelerated grain boundary oxygen(SAGBO) during serving;thus, the intergranular fracture morphology degree increases with duration of service(almost 40% increase from the fractured surface). In addition, the strength of alloy will be gradually enhanced when the γ'phase becomes relatively bulky with serving time increasing due to considerable distortion of the dislocations as a result of the spacing of individual particles, in which any movement of the dislocation will have to overcome a larger number of obstacles per unit length.
基金supported by the National "Twelfth Five-Year Plan" Key Technologies Program of China (2011DAE22B01)
文摘As reported in our previous works, a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures. In Mg-7Gd-5Y-1Nd-0.5Zr alloy, the β pre- cipitate phase was assumed to he one of the main strengthening phases in peak-aged samples. This study aimed to determine the crys- tal structure and orientation relationship of the β precipitate phase in Mg-7Gd-5Y-INd-0.5Zr alloy using transmission electron mi- croscopy and high-resolution electron microscopy. The results indicated that the β precipitate had a face-centered cubic structure with a lattice parameter of a=2.22 nm. The orientation relationship between the β precipitate phase and the ct-Mg matrix was （i-12）β（1-100）α, [110]β[0001 ]α. Theβ plates formed on prismatic planes could play an important role in alloy strengthening by proving effective barriers to gliding dislocations. A single β plate often contained several domains of （1 11）β twin-related variants. A composition of Mgs（Y0.4Gdo.4Nd0.2） was suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.
文摘The minor precipitations caused by B and Zr which are the normal constituents of U720 Li alloy have been studied by analyzing the solidification process and the composition evolution. The present study aims to supply the elementary information about the existing form of B and Zr in the as-cast microstructure, which is helpful for the subsequent processing, such as homogenization treatment. The M_3B_2 and Ni_5Zr phases were observed in the U720 Li alloy in as-cast state, which were usually accompanying with each other together with g-Ni_3 Ti phase at the edge of eutectic（γ＋γ＇）. Combining the DTA analysis and heating and quenching tests, the solidification sequence was determined to be the following： c matrix, eutectic（γ＋γ＇）, g-Ni_3Ti, M_3B_2 and Ni_5Zr. The in situ composition analysis by EDS and EPMA revealed that the precipitation and microstructure were governed by the composition evolution in the liquids. The solidification of c matrix increased the Ti concentration in the residual liquids and resulted in the eutectic（γ＋γ＇） formation; the（γ＋γ＇） formation increased the Ti/Al radio in the liquids and the g-Ni_3Ti was formed in front of the eutectic（γ＋γ＇）; the g-Ni_3Ti precipitation consumed up Al and Ti and increased the concentration of B, Mo and Cr, and M_3B_2 boride is formed;the previous precipitation of the phases consumed up most of the elements other than Ni and Zr, and Ni_5Zr is formed finally. The melting points are in the ranges of 1130–1140 °C for Ni_5Zr phase, 1180–1190 °C for M_3B_2 boride and1190–1200 °C for g-Ni_3Ti phase.
基金supported by the National Key Research and Development Program of China(No.2022YFB3803800)the National Natural Science Foundation of China(Nos.51971197 and 52071281)+4 种基金the Basic Innovation Research Project in Yanshan University(No.2022LGZD004)the China Postdoctoral Science Foundation(No.2023M742945)the Postdoctoral Research Project of Hebei Province(No.B2023003023)the Subsidy for Hebei Key Laboratory of Applied Chemistry after Operation Performance(No.22567616H)the Special Project for Local Science and Technology Development Guided by the Central Government of China(No.236Z1406G).
文摘La–Mg–Ni-based hydrogen storage alloys have excellent hydrogen storage properties.This work reports the hydrogen storage performance of a series of A_(2)B_(7)-type La_(0.96)Mg_(0.04)N_(i3.34)Al_(0.13)alloy and La_(0.96-x)Y_(x)Mg_(0.04)Ni_(3.47–0.6x)Al_(0.6x)(x=0,0.22,0.33,0.44)alloys,and explores the effect of Y and Al element combined substitution on the microstructure and hydrogen storage performance of A_(2)B_(7)-type La–Mg–Ni-based alloys.The alloys are composed of Ce_(2)Ni_(7)phase and LaNi_(5)phase.With the increase of x,the cell volume of Ce_(2)Ni_(7)phase decreases,while that of LaNi_(5)phase increases,indicating that Y atom mainly enters Ce_(2)Ni_(7)phase and Al atom mainly enters LaNi_(5)phase.An appropriate amount of co-substitution increases the hydrogen storage capacity and reduces the hydrogen absorption/desorption plateau pressure hysteresis of the alloy.When x=0.44,the hydrogen storage capacity of the alloy is 1.449 wt%,and the hysteresis coefficient is 0.302.The cell volume of Ce_(2)Ni_(7)phase and LaNi_(5)phase expands to different degrees after 20 absorption/desorption cycles.With the increase of x,the volume expansion rate decreases,and the cycle capacity retention rate also gradually decreases.This is related to the amorphization of Ce_(2)Ni_(7)phase.When x=0.22,the capacity retention rate of the alloy is 91.4%.
