采用硬度测试仪、透射电镜(Transmission electron microscopy,TEM)、X射线衍射仪(X-ray diffraction,XRD)等手段研究了冷轧过程中AlFeMn合金板材的硬度、微观组织、织构变化。AlFeMn合金的显微硬度先随冷轧率增加而增加,在冷轧率为82%...采用硬度测试仪、透射电镜(Transmission electron microscopy,TEM)、X射线衍射仪(X-ray diffraction,XRD)等手段研究了冷轧过程中AlFeMn合金板材的硬度、微观组织、织构变化。AlFeMn合金的显微硬度先随冷轧率增加而增加,在冷轧率为82%时,硬度达到峰值;然后硬度随冷轧率增加而下降。与此同时,合金中的位错密度明显降低,出现多边化亚晶。结果表明,冷轧过程中,AlFeMn合金存在由加工硬化转变为加工软化的行为。加工软化在中低应变量(≤78%冷轧率)时,copper、S取向含量随冷轧率增加略有增加,而brass取向含量基本保持不变;在达到82%冷轧率时,copper、S、brass取向含量明显急剧增加,在冷轧率超过84%后含量又急剧降低。Cube取向含量在加工硬化期间一直降低,在加工软化后期含量略有增加。结果表明,加工软化的发生伴随有晶粒取向的变化。展开更多
TIG welding experiments of TC2 titanium alloy sheet was carried out,and the well-formed weld was obtained.After welding process,the cross-section microstructure,mechanical properties,fracture morphology and quality in...TIG welding experiments of TC2 titanium alloy sheet was carried out,and the well-formed weld was obtained.After welding process,the cross-section microstructure,mechanical properties,fracture morphology and quality inspection of the joint were studied.The results show that the microstructure of the weld consists of a large number of acicularα′andβblock.The microhardness curve shows that the microhardness value in the fusion zone(FZ)of the joint is significantly higher than that in the heat affected zone(HAZ)and the base metal(BM),and the microhardness of the base metal is the lowest.The tensile strength of the joint is equivalent to that of the base metal,and the fracture morphology shows that the fracture mechanism of the joint is mixed ductile-brittle fracture mode.The weld quality is excellent through chemical inspection,penetrant inspection and X-ray inspection.展开更多
The temperature evolution of the crystal structure for Nd_(0.5)Sr_(0.5)MnO_3 has been investigated by powder XRD between 125 Kand 725K.The structure can be described with a monoclinic symmetry(space group P21/m)in the...The temperature evolution of the crystal structure for Nd_(0.5)Sr_(0.5)MnO_3 has been investigated by powder XRD between 125 Kand 725K.The structure can be described with a monoclinic symmetry(space group P21/m)in the temperature range of 125—175 K,while with the increase in temperature between 175 Kand 575 Kthe structure involves a higher orthorhombic symmetry(space group Imma).The rhombohedral structure with space group R-3cis observed at high temperature region of 575—725K.The increase in the magnetization at low temperatures can be ascribed to the field-induced short-range magnetic order of the Nd3+ions.The dc and ac susceptibility data show some anomalies around the FM-PM transition region which can be attributed to the glass behavior and magnetic relaxation.展开更多
The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding(FSW)joints prepared in water/air.For comparable analysis,the submerged FSW(SFSW)and conventional FSW are bot...The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding(FSW)joints prepared in water/air.For comparable analysis,the submerged FSW(SFSW)and conventional FSW are both conducted on 6061-T6 aluminum alloy plates at the combination rotation speed of 800 r/min and the traverse rate of 50 mm/min.The results show that a greatest grain refinement is achieved by SFSW,which is remarkably smaller than that of the base material(BM)and air FSW(AFSW)samples,leading to a significant improvement of tensile strength from 202.5 MPa in the AFSW sample to 232 MPa in the SFSW sample.展开更多
Ti-4Al-1.5Mn dual phase titanium alloy sheet was spot welded by pneumatic resistance spot welder.The effects of different welding parameters on shear load and nugget diameter were studied.The results show that the max...Ti-4Al-1.5Mn dual phase titanium alloy sheet was spot welded by pneumatic resistance spot welder.The effects of different welding parameters on shear load and nugget diameter were studied.The results show that the maximum shear load of solder joint increases first and then decreases with the increase of electrode pressure and welding current,while the nugget diameter increases with the increase of electrode pressure and welding current.Electrode pressure of 0.20 MPa and welding current of 46 A are the optimal process parameters,under which the maximum shear load of solder joint reaches 8.80 kN.The microstructure of nugget zone is coarse acicular martensite,and the solder joints fail in a mixed mode of intergranular brittle-ductile fracture.展开更多
Double perovskite oxide Sr_2FeMoO_6 powder is prepared by a solid state reaction method.The microwave absorption properties of Sr_2FeMoO_6 and paraffin wax composites are studied in the frequency range of 2—18GHz at ...Double perovskite oxide Sr_2FeMoO_6 powder is prepared by a solid state reaction method.The microwave absorption properties of Sr_2FeMoO_6 and paraffin wax composites are studied in the frequency range of 2—18GHz at room temperature.The optimum absorption-36.7dB is achieved at 17.7GHz with a matching thickness of 5.0mm,which indicates that Sr_2FeMoO_6/paraffin composites can be potential microwave absorbers in a relatively high frequency range.The excellent microwave absorption properties are attributed to the good electromagnetic match between dielectric loss and magnetic loss.The dielectric loss is considered to be caused by orientation polarization and interfacial polarization,while the magnetic loss is caused by natural resonance in the low frequency range,eddy current loss as well as exchange resonance in the high frequency range.展开更多
利用光学显微镜(Optical microscope,OM)、X射线衍射仪(X-ray diffractometer,XRD)、扫描电子显微镜(Scanning electron microscope,SEM)、能谱分析仪(Energy dispersive spectrometer,EDS)、透射电镜(Transmission electron microscope...利用光学显微镜(Optical microscope,OM)、X射线衍射仪(X-ray diffractometer,XRD)、扫描电子显微镜(Scanning electron microscope,SEM)、能谱分析仪(Energy dispersive spectrometer,EDS)、透射电镜(Transmission electron microscope,TEM)和电子万能试验机等手段对传统砂型重力铸造方法制备的EV31A合金的显微组织和性能进行了深入研究。实验结果表明:铸态EV31A合金的显微组织由α-Mg和α-Mg+Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)共晶相组成,由于稀土元素含量较少,共晶反应发生在α-Mg结晶后期,表现为除少量固溶于α-Mg基体中,含稀土元素的Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)相主要分布在α-Mg的晶界处。Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)相为bcc结构,晶格常数为0.285 nm,呈鱼骨状,尺寸在数十微米。合金中α-Mg基体的晶粒尺寸为56.8μm。EV31A铸态合金的抗拉强度、屈服强度和延伸率分别为207 MPa、124 MPa和7.0%。合金具有优异力学性能主要归因于Zr元素所带来的细晶强化,Gd、Nd、Zr等溶质原子的固溶强化,共晶Mg_(41)(Nd_(0.9),Gd_(0.1))_(5)相所带来的第二相强化等多种强化方式的协同作用。展开更多
文摘采用硬度测试仪、透射电镜(Transmission electron microscopy,TEM)、X射线衍射仪(X-ray diffraction,XRD)等手段研究了冷轧过程中AlFeMn合金板材的硬度、微观组织、织构变化。AlFeMn合金的显微硬度先随冷轧率增加而增加,在冷轧率为82%时,硬度达到峰值;然后硬度随冷轧率增加而下降。与此同时,合金中的位错密度明显降低,出现多边化亚晶。结果表明,冷轧过程中,AlFeMn合金存在由加工硬化转变为加工软化的行为。加工软化在中低应变量(≤78%冷轧率)时,copper、S取向含量随冷轧率增加略有增加,而brass取向含量基本保持不变;在达到82%冷轧率时,copper、S、brass取向含量明显急剧增加,在冷轧率超过84%后含量又急剧降低。Cube取向含量在加工硬化期间一直降低,在加工软化后期含量略有增加。结果表明,加工软化的发生伴随有晶粒取向的变化。
基金the Priority Academic Program Development of Jiangsu Higher Education Institution and Beijing Institute of Aeronautical Materials(No.KZ82171509).
文摘TIG welding experiments of TC2 titanium alloy sheet was carried out,and the well-formed weld was obtained.After welding process,the cross-section microstructure,mechanical properties,fracture morphology and quality inspection of the joint were studied.The results show that the microstructure of the weld consists of a large number of acicularα′andβblock.The microhardness curve shows that the microhardness value in the fusion zone(FZ)of the joint is significantly higher than that in the heat affected zone(HAZ)and the base metal(BM),and the microhardness of the base metal is the lowest.The tensile strength of the joint is equivalent to that of the base metal,and the fracture morphology shows that the fracture mechanism of the joint is mixed ductile-brittle fracture mode.The weld quality is excellent through chemical inspection,penetrant inspection and X-ray inspection.
基金supported by the Jiangsu Provincial Natural Science Foundation(No.BK20141411)
文摘The temperature evolution of the crystal structure for Nd_(0.5)Sr_(0.5)MnO_3 has been investigated by powder XRD between 125 Kand 725K.The structure can be described with a monoclinic symmetry(space group P21/m)in the temperature range of 125—175 K,while with the increase in temperature between 175 Kand 575 Kthe structure involves a higher orthorhombic symmetry(space group Imma).The rhombohedral structure with space group R-3cis observed at high temperature region of 575—725K.The increase in the magnetization at low temperatures can be ascribed to the field-induced short-range magnetic order of the Nd3+ions.The dc and ac susceptibility data show some anomalies around the FM-PM transition region which can be attributed to the glass behavior and magnetic relaxation.
文摘The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding(FSW)joints prepared in water/air.For comparable analysis,the submerged FSW(SFSW)and conventional FSW are both conducted on 6061-T6 aluminum alloy plates at the combination rotation speed of 800 r/min and the traverse rate of 50 mm/min.The results show that a greatest grain refinement is achieved by SFSW,which is remarkably smaller than that of the base material(BM)and air FSW(AFSW)samples,leading to a significant improvement of tensile strength from 202.5 MPa in the AFSW sample to 232 MPa in the SFSW sample.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institution and Beijing Institute of Aeronautical Materials(No.KZ82171509)。
文摘Ti-4Al-1.5Mn dual phase titanium alloy sheet was spot welded by pneumatic resistance spot welder.The effects of different welding parameters on shear load and nugget diameter were studied.The results show that the maximum shear load of solder joint increases first and then decreases with the increase of electrode pressure and welding current,while the nugget diameter increases with the increase of electrode pressure and welding current.Electrode pressure of 0.20 MPa and welding current of 46 A are the optimal process parameters,under which the maximum shear load of solder joint reaches 8.80 kN.The microstructure of nugget zone is coarse acicular martensite,and the solder joints fail in a mixed mode of intergranular brittle-ductile fracture.
基金supported by the Jiangsu Provincial Natural Science Foundation(No.BK20141411)a project funded by Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),Nanjing,China
文摘Double perovskite oxide Sr_2FeMoO_6 powder is prepared by a solid state reaction method.The microwave absorption properties of Sr_2FeMoO_6 and paraffin wax composites are studied in the frequency range of 2—18GHz at room temperature.The optimum absorption-36.7dB is achieved at 17.7GHz with a matching thickness of 5.0mm,which indicates that Sr_2FeMoO_6/paraffin composites can be potential microwave absorbers in a relatively high frequency range.The excellent microwave absorption properties are attributed to the good electromagnetic match between dielectric loss and magnetic loss.The dielectric loss is considered to be caused by orientation polarization and interfacial polarization,while the magnetic loss is caused by natural resonance in the low frequency range,eddy current loss as well as exchange resonance in the high frequency range.
