The paper reports on the atomic investigation aboutβphase in Mg_(96)Gd_(2)Y_(1)Ni_(1) alloy by using the first-principles study and the high-angle annular dark-field scanning transmission electron microscope(HAADF-ST...The paper reports on the atomic investigation aboutβphase in Mg_(96)Gd_(2)Y_(1)Ni_(1) alloy by using the first-principles study and the high-angle annular dark-field scanning transmission electron microscope(HAADF-STEM)corrected by atomic Cs.By using HAADF-STEM,the rectangularβphases were observed in the underage and peak aging stages in Mg_(96)Gd_(2)Y_(1)Ni_(1) alloy.Theβphase could be precipitated from the previously precipitatedβphase,and theβphase grew in steps when it was precipitated.A special transition structure of three atomic layer thicknesses was first observed at the edge of theβphase and the structure of this interface is probably as theβ/Mg_(1) interface for the analysis of thermodynamic characterization and electronic characterization.Theβ'phase and theβ_(H) structure were precipitated only at the edge of the length directions of theβphase.Theβ'phase continues to grow into aβphase directly without the formation ofβ_(1) phase,resulting in an increase in the length of theβphase,which is discovered for the first time.展开更多
Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ult...Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ultrathin films induced by stretching was investigated using transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The results show that stretching can enhance the crystallinity and increase the average thickness of the lamellae.A fullα-βphase transition can be achieved for PVDF ultrathin films of 20.6%βphase stretched to aλ(stretching ratio)of 1.5,while fewαphases still exist for ultrathin films of 35.0%βphase,together with bent and tilted lamellae.Compared to thicker PVDF films undergoing stretching-inducedα-βphase transition,the higherα-βphase transition efficiency of the PVDF ultrathin films can be attributed to the parallel aligned lamellar structure.Moreover,a higherβ-phase content can suppressα-βphase transition because of the stress concentration effect ofβ-phase.Ultimately,these results provide valuable insights into the stretching-inducedα-βphase transition of PVDF ultrathin films.展开更多
The phase transformation behavior of an as-cast Ti-42Al-5 Mn(at.%)alloy after subsequent quenching from 1380℃to 1000℃was investigated based on the differential thermal analysis(DTA),electron probe micro analyzer-bac...The phase transformation behavior of an as-cast Ti-42Al-5 Mn(at.%)alloy after subsequent quenching from 1380℃to 1000℃was investigated based on the differential thermal analysis(DTA),electron probe micro analyzer-backscattered electrons(EPMA-BSE),transmission electron microscope(TEM)and X-ray diffraction(XRD).The results show that,the solidification path can be summarized as follows:Liquid→Liquid+β→β→β→α→β+α+γ→βo+α2+γ→βo+γ+α2/γ→βo+γ+α2/γ+βo,sec,with the phase transformationα→βtemperature(Tβ)=1311℃,phase transformationγ→βtemperature of(Tγsolv)=1231℃,phase transformationα2→αorβo→βtemperature(Tα2→α/Tβo→β)=1168 C,eutectoid temperature(Teut)=1132℃and T(α2/γ→βo,sec)≈1120℃.In comparison with Ti-42 Al alloy,the Teut and Tγsolv are slightly increased while both the Tp is decreased obviously by 5%Mn addition.When quenched from the temperature of 1380-1260℃,the martensitic transformationβ→α'could occur to form the needlelike martensite structure inβarea.This kind of martensitic structure is much obvious with the increase of temperature from 1260℃to 1380℃.When the temperature is below Tγsolv(1231℃),theγgrains would nucleate directly from theβphase.For the temperature slightly lower than T(eut)(1132℃),the dottedβ(o,sec)phases could nucleate in the lamellar colonies besides theγlamellae precipitated withinα2 phase.Finally,at room-temperature(RT),the alloy exhibits(po+α2+γ)triple phase with microstructure ofβo+lamellae+γ,of which the lamellar structure consists ofα2,γandβo,sec phases.The phase transformation mechanisms in this alloy,involvingβ→α',β→γ,α2→α2/γandα2→βo,sec were discussed.展开更多
In this study,non-toxic in-situβphases of reinforced Ti/Zr-based bulk metallic glass matrix composites(BMGCs)of(Ti_(0.65)Zr_(0.35))100-xCux(x=5,10,15 at.%)are fabricated via selective laser melting.The effect of Cu c...In this study,non-toxic in-situβphases of reinforced Ti/Zr-based bulk metallic glass matrix composites(BMGCs)of(Ti_(0.65)Zr_(0.35))100-xCux(x=5,10,15 at.%)are fabricated via selective laser melting.The effect of Cu content on phase formation,microstructure,and mechanical properties is investigated.The average volume fraction and width of theβphase decreases with increasing Cu content,while a more amorphous phase and the(Ti,Zr)_(2)Cu phase forms.In the center zone of the molten pool,theβphase grows in the direction of the temperature gradient,and the amorphous phase distributes among theβphases.This occurs using:sphere morphology(for x=5),a more continuous elongated sphere and network morphology(for x=10),and network morphology(for x=15),respectively.In the edge zone of the molten pool,due to the smaller cooling rate and the existence of a partially molten zone,theβphase becomes coarser,and an amorphous phase forms for more continuous networks.Furthermore,the hardness improves significantly with increasing Cu content.No crack is found for x=5.Although the average volume fraction of theβphase for x=5 is about 90%,the compression yield strength is 1386±64 MPa,reaching to an average level of conventionally fabricated counterparts,due to finer microstructure,and twinning and martensitic transformation of theβphase.展开更多
目的评估不同酸洗液酸洗预处理后六铝四钒钛(Ti-6Al-4V)合金的微观形貌和耐腐蚀性能的变化,以确定适合作为植入性生物材料的钛合金的酸洗方法。方法采用接触角测量、扫描电子显微镜、X射线能谱仪、电化学测试等研究HF+H 2 SO 4酸洗液、H...目的评估不同酸洗液酸洗预处理后六铝四钒钛(Ti-6Al-4V)合金的微观形貌和耐腐蚀性能的变化,以确定适合作为植入性生物材料的钛合金的酸洗方法。方法采用接触角测量、扫描电子显微镜、X射线能谱仪、电化学测试等研究HF+H 2 SO 4酸洗液、HF+HNO 3酸洗液、HF酸洗液对Ti-6Al-4V合金试样进行酸洗后的微观形貌、亲水性能及耐腐蚀性能等。结果Ti-6Al-4V合金试样在3种酸洗液中表现为不同的酸洗速率:HF+H 2 SO 4酸洗组为0.088μm/s、HF+HNO 3酸洗组为0.064μm/s、HF酸洗组为0.097μm/s。3组试样均表现出特征性的α+β相微观形貌,HF+HNO 3酸洗组和HF酸洗组β相占比大于HF+H 2 SO 4酸洗组,HF酸洗组出现了氢化物相,光学显微镜下HF+HNO 3酸洗组试样点蚀现象最少;在模拟体液中做耐腐蚀性能测试,自腐蚀电位结果为去离子水组>HF+HNO 3酸洗组>HF+H 2 SO 4酸洗组>HF酸洗组。结论经HF+HNO 3酸洗的Ti-6Al-4V合金试样表面平滑,接触角为47.63°±2.40°、失重率为1.11%±0.08%,可均匀去除有机杂质及氧化膜,C/Ti与O/Ti值分别下降至0.047±0.001、0.040±0.008,且有较高耐腐蚀性能,自腐蚀电位为-0.676 V。可选用HF+HNO 3酸洗液以获得耐腐蚀性能较高且表面清洁、均匀的植入性生物Ti-6Al-4V合金。展开更多
The bulk interaction between two phases in AgI(η-Al_(2)O_(3) orα-Fe_(2)O_(3))has been investigated by means of electrical conductivity,DTA and Mössbauer spectra.It shows that bothα→βphase transition of AgI a...The bulk interaction between two phases in AgI(η-Al_(2)O_(3) orα-Fe_(2)O_(3))has been investigated by means of electrical conductivity,DTA and Mössbauer spectra.It shows that bothα→βphase transition of AgI and Morin transition ofα-Fe_(2)O_(3) influence each other.展开更多
为有效调控有机复合膜压电性能,本研究采用旋涂法制备出结构致密的PVDF/BaTiO_(3)有机复合膜,形成明显的1-3型结构。XRD拟合结果显示在质量分数15%制备条件下,PVDF形成了良好的结晶态,此时膜内β相含量较高。通过压电相图验证了PVDF/BaT...为有效调控有机复合膜压电性能,本研究采用旋涂法制备出结构致密的PVDF/BaTiO_(3)有机复合膜,形成明显的1-3型结构。XRD拟合结果显示在质量分数15%制备条件下,PVDF形成了良好的结晶态,此时膜内β相含量较高。通过压电相图验证了PVDF/BaTiO_(3)有机复合膜压电性为真实存在,当质量分数为15%时,复合膜压电响应结果优于其他,输出电压最大可达105 m V左右,这与XRD拟合结果中显示的该浓度下β相含量最高有关。本研究为调控有机压电薄膜性能提供了一条可行性思路。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
The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission el...The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.51825101)the National Key Research and Development Program of China(Grant No.2016YFB0701201)。
文摘The paper reports on the atomic investigation aboutβphase in Mg_(96)Gd_(2)Y_(1)Ni_(1) alloy by using the first-principles study and the high-angle annular dark-field scanning transmission electron microscope(HAADF-STEM)corrected by atomic Cs.By using HAADF-STEM,the rectangularβphases were observed in the underage and peak aging stages in Mg_(96)Gd_(2)Y_(1)Ni_(1) alloy.Theβphase could be precipitated from the previously precipitatedβphase,and theβphase grew in steps when it was precipitated.A special transition structure of three atomic layer thicknesses was first observed at the edge of theβphase and the structure of this interface is probably as theβ/Mg_(1) interface for the analysis of thermodynamic characterization and electronic characterization.Theβ'phase and theβ_(H) structure were precipitated only at the edge of the length directions of theβphase.Theβ'phase continues to grow into aβphase directly without the formation ofβ_(1) phase,resulting in an increase in the length of theβphase,which is discovered for the first time.
基金financially supported from the National Natural Science Foundation of China(Nos.52203026 and 52027804)。
文摘Highly oriented poly(vinylidene fluoride)(PVDF)ultrathin films with differentβ-phase contents were prepared using the melt-draw method.The effect ofβ-phase content onα-βphase transition of highly oriented PVDF ultrathin films induced by stretching was investigated using transmission electron microscopy(TEM)and Fourier transform infrared(FTIR)spectroscopy.The results show that stretching can enhance the crystallinity and increase the average thickness of the lamellae.A fullα-βphase transition can be achieved for PVDF ultrathin films of 20.6%βphase stretched to aλ(stretching ratio)of 1.5,while fewαphases still exist for ultrathin films of 35.0%βphase,together with bent and tilted lamellae.Compared to thicker PVDF films undergoing stretching-inducedα-βphase transition,the higherα-βphase transition efficiency of the PVDF ultrathin films can be attributed to the parallel aligned lamellar structure.Moreover,a higherβ-phase content can suppressα-βphase transition because of the stress concentration effect ofβ-phase.Ultimately,these results provide valuable insights into the stretching-inducedα-βphase transition of PVDF ultrathin films.
文摘The phase transformation behavior of an as-cast Ti-42Al-5 Mn(at.%)alloy after subsequent quenching from 1380℃to 1000℃was investigated based on the differential thermal analysis(DTA),electron probe micro analyzer-backscattered electrons(EPMA-BSE),transmission electron microscope(TEM)and X-ray diffraction(XRD).The results show that,the solidification path can be summarized as follows:Liquid→Liquid+β→β→β→α→β+α+γ→βo+α2+γ→βo+γ+α2/γ→βo+γ+α2/γ+βo,sec,with the phase transformationα→βtemperature(Tβ)=1311℃,phase transformationγ→βtemperature of(Tγsolv)=1231℃,phase transformationα2→αorβo→βtemperature(Tα2→α/Tβo→β)=1168 C,eutectoid temperature(Teut)=1132℃and T(α2/γ→βo,sec)≈1120℃.In comparison with Ti-42 Al alloy,the Teut and Tγsolv are slightly increased while both the Tp is decreased obviously by 5%Mn addition.When quenched from the temperature of 1380-1260℃,the martensitic transformationβ→α'could occur to form the needlelike martensite structure inβarea.This kind of martensitic structure is much obvious with the increase of temperature from 1260℃to 1380℃.When the temperature is below Tγsolv(1231℃),theγgrains would nucleate directly from theβphase.For the temperature slightly lower than T(eut)(1132℃),the dottedβ(o,sec)phases could nucleate in the lamellar colonies besides theγlamellae precipitated withinα2 phase.Finally,at room-temperature(RT),the alloy exhibits(po+α2+γ)triple phase with microstructure ofβo+lamellae+γ,of which the lamellar structure consists ofα2,γandβo,sec phases.The phase transformation mechanisms in this alloy,involvingβ→α',β→γ,α2→α2/γandα2→βo,sec were discussed.
基金supported by the National Key Research and Development Plan of China(No.2018YFB0704101)the Fundamental Research Funds for the Central Universities(No.3102019ZX013)the Planning Programme of Shan Xi Province’s Co-Ordination and Innovation Project of Science and Technology(No.2016KTZDCY02-02)。
文摘In this study,non-toxic in-situβphases of reinforced Ti/Zr-based bulk metallic glass matrix composites(BMGCs)of(Ti_(0.65)Zr_(0.35))100-xCux(x=5,10,15 at.%)are fabricated via selective laser melting.The effect of Cu content on phase formation,microstructure,and mechanical properties is investigated.The average volume fraction and width of theβphase decreases with increasing Cu content,while a more amorphous phase and the(Ti,Zr)_(2)Cu phase forms.In the center zone of the molten pool,theβphase grows in the direction of the temperature gradient,and the amorphous phase distributes among theβphases.This occurs using:sphere morphology(for x=5),a more continuous elongated sphere and network morphology(for x=10),and network morphology(for x=15),respectively.In the edge zone of the molten pool,due to the smaller cooling rate and the existence of a partially molten zone,theβphase becomes coarser,and an amorphous phase forms for more continuous networks.Furthermore,the hardness improves significantly with increasing Cu content.No crack is found for x=5.Although the average volume fraction of theβphase for x=5 is about 90%,the compression yield strength is 1386±64 MPa,reaching to an average level of conventionally fabricated counterparts,due to finer microstructure,and twinning and martensitic transformation of theβphase.
文摘The bulk interaction between two phases in AgI(η-Al_(2)O_(3) orα-Fe_(2)O_(3))has been investigated by means of electrical conductivity,DTA and Mössbauer spectra.It shows that bothα→βphase transition of AgI and Morin transition ofα-Fe_(2)O_(3) influence each other.
文摘为有效调控有机复合膜压电性能,本研究采用旋涂法制备出结构致密的PVDF/BaTiO_(3)有机复合膜,形成明显的1-3型结构。XRD拟合结果显示在质量分数15%制备条件下,PVDF形成了良好的结晶态,此时膜内β相含量较高。通过压电相图验证了PVDF/BaTiO_(3)有机复合膜压电性为真实存在,当质量分数为15%时,复合膜压电响应结果优于其他,输出电压最大可达105 m V左右,这与XRD拟合结果中显示的该浓度下β相含量最高有关。本研究为调控有机压电薄膜性能提供了一条可行性思路。
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Projects(52274402,52174381)supported by the National Natural Science Foundation of China。
文摘The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.
