The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are...The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field：（i） the GB plane area determines the current carrying cross section;（ii） the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force.Furthermore,the vortex motion in a bicrystal GB is studied by investigating transverse（Hall） and longitudinal current–voltage characteristics（I–Vxx and I–Vxy）.It is found that the I–Vxx curve diverges from linearity at a high driving current,while the I–Vxy curve keeps nearly linear,which indicates the vortices inside the GB break out of the GB by Lorentz force.展开更多
Since the discovery of high-temperature superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub>（YBCO） people aremuch concerned about its microwave surface resistance. It was fou...Since the discovery of high-temperature superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub>（YBCO） people aremuch concerned about its microwave surface resistance. It was found that although themicrowave surface resistance of c-axis oriented YBCO thin films is an order of magnitudelower than Cu, it is much higher than the value predicted by the BCS theory, and also展开更多
采用Gleeble1500热模拟试验机,研究不同热输入对Q890高强钢焊接热影响区粗晶区的微观组织和韧性影响规律.结果表明,随着热输入的增加,粗晶区的微观组织表现出从马氏体组织向马氏体、贝氏体的混合组织,再向贝氏体、粒状贝氏体的混合组织...采用Gleeble1500热模拟试验机,研究不同热输入对Q890高强钢焊接热影响区粗晶区的微观组织和韧性影响规律.结果表明,随着热输入的增加,粗晶区的微观组织表现出从马氏体组织向马氏体、贝氏体的混合组织,再向贝氏体、粒状贝氏体的混合组织的转变.当热输入为19.7 k J/cm时,冲击吸收功最高为83 J,主要原因是由于先相贝氏体分割后相马氏体,大角度晶界密度最大,改善了冲击韧性.当热输入较高时,粗晶区脆化的原因是由于M-A组元呈链状分布,造成局部应力集中,成为裂纹起裂和扩展的主要通道.展开更多
塑性变形诱导晶粒细化过程中存在着复杂的变形机制,但是当达到稳定态之后进一步变形不会细化材料的微观结构。研究表明,金属材料能够制备的最小晶粒尺寸的微观结构既取决于材料的层错能、晶体结构等内部属性,也受到应变、应变速率、变...塑性变形诱导晶粒细化过程中存在着复杂的变形机制,但是当达到稳定态之后进一步变形不会细化材料的微观结构。研究表明,金属材料能够制备的最小晶粒尺寸的微观结构既取决于材料的层错能、晶体结构等内部属性,也受到应变、应变速率、变形温度等外部条件的影响。通过高应变速率(500~1500 s-1)的霍普金森实验研究了1060工业纯铝在变形过程中微观结构和晶体取向差与应变速率之间的关系,微观结构和晶体取向分别用FEI Verios 460 SEM和FEI Nano SEM Nova 430进行表征。结果表明,随着应变速率的增加,晶粒尺寸明显得到细化,同时晶粒的择优取向增加;另外,材料形成了大量小角度晶界,并且硬度达到了430 MPa。因此,对高层错能低熔点的纯铝来说,常温条件下高应变速率能够促进小角度晶界的形成并且能够提升材料的硬度。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61501222,61371036,and 61571219)the School Scientific Research Fund of Nanjing Institute of Technology,China(Grant Nos.YKJ201418)
文摘The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field：（i） the GB plane area determines the current carrying cross section;（ii） the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force.Furthermore,the vortex motion in a bicrystal GB is studied by investigating transverse（Hall） and longitudinal current–voltage characteristics（I–Vxx and I–Vxy）.It is found that the I–Vxx curve diverges from linearity at a high driving current,while the I–Vxy curve keeps nearly linear,which indicates the vortices inside the GB break out of the GB by Lorentz force.
基金Project supported by the National Center for Research and Development on Superconductivity.
文摘Since the discovery of high-temperature superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub>（YBCO） people aremuch concerned about its microwave surface resistance. It was found that although themicrowave surface resistance of c-axis oriented YBCO thin films is an order of magnitudelower than Cu, it is much higher than the value predicted by the BCS theory, and also
文摘采用Gleeble1500热模拟试验机,研究不同热输入对Q890高强钢焊接热影响区粗晶区的微观组织和韧性影响规律.结果表明,随着热输入的增加,粗晶区的微观组织表现出从马氏体组织向马氏体、贝氏体的混合组织,再向贝氏体、粒状贝氏体的混合组织的转变.当热输入为19.7 k J/cm时,冲击吸收功最高为83 J,主要原因是由于先相贝氏体分割后相马氏体,大角度晶界密度最大,改善了冲击韧性.当热输入较高时,粗晶区脆化的原因是由于M-A组元呈链状分布,造成局部应力集中,成为裂纹起裂和扩展的主要通道.
文摘塑性变形诱导晶粒细化过程中存在着复杂的变形机制,但是当达到稳定态之后进一步变形不会细化材料的微观结构。研究表明,金属材料能够制备的最小晶粒尺寸的微观结构既取决于材料的层错能、晶体结构等内部属性,也受到应变、应变速率、变形温度等外部条件的影响。通过高应变速率(500~1500 s-1)的霍普金森实验研究了1060工业纯铝在变形过程中微观结构和晶体取向差与应变速率之间的关系,微观结构和晶体取向分别用FEI Verios 460 SEM和FEI Nano SEM Nova 430进行表征。结果表明,随着应变速率的增加,晶粒尺寸明显得到细化,同时晶粒的择优取向增加;另外,材料形成了大量小角度晶界,并且硬度达到了430 MPa。因此,对高层错能低熔点的纯铝来说,常温条件下高应变速率能够促进小角度晶界的形成并且能够提升材料的硬度。
