大塑性变形制备超细晶铝锂合金的组织及力学性能研究进展

综述了大塑性变形工艺制备超细晶铝锂合金的显微组织及其力学性能,分析了大塑性变形过程中铝锂合金的组织演变及其影响因素。铝锂合金的强化机制主要是基于析出强化,结合大塑性变形得到的超细晶粒组织可以显著提高强度和塑性,并得到优异的超塑性。表明大塑性变形加工铝锂合金,尤其是等通道挤压制备的超细晶铝镁锂合金在超塑性工业具有广阔的发展前景。     

Influence of grain boundary sliding on diffusion in yttria doped zirconia

Grain boundary sliding during high temperature deformation can lead to stress concentrations and an enhancement of diffusion in mobile boundaries. Experiments were conducted on a fine grained 3 mol% yttria stabilized tetragonal zirconia, under conditions associated with superplastic flow involving grain boundary sliding. Tracer diffusion studies under creep conditions and without load indicate that there is no enhancement in either the lattice or grain boundary diffusivities. The experimental creep data are consistent with an interface controlled diffusion creep mechanism.     

Paradoxes of Severe Plastic Deformation

Severe plastic deformation (SPD) can lead to emergence of microstructural features and properties in materials which are fundamentally different from the ones well known for conventional cold deformation. In particular, the instances of unusual phase transformations resulting in development of highly metastable states associated with formation of supersaturated solid solutions, disordering or amorphization and their further decomposition during heating, high thermal stability of the SPD‐produced nanostructures, and the paradox of strength and ductility in some SPD‐processed metals and alloys are discussed.     

大晶粒超塑性变形机理的研究

本文通过对供应状态铝锰β-黄铜超塑性的系统研究,探讨了其在大晶粒组织条件下的超塑性变形机理;应用刻痕实验和金相组织观察方法,发现了大量亚晶界和亚晶界的运动。根据实验结果分析和理论计算提出了亚晶界的移动和滑动是大晶粒超塑性变形的主导机制,由测量得知晶界滑动变形对总变形的贡献仅为～10％,这说明晶界滑动是调节机制。     

Superplasticity Enhanced by Two-stage Deformation in a Hot-extruded AZ61 Magnesium Alloy

A two-stage strain rate deformation method is proposed to enhance the superplasticity in a hot extruded AZ61 alloy. In the stage-one of deformation, a relatively high strain rate was applied in order to obtain fine grains through dynamic recrystallization. The optimum strain rate for DRX at 300℃ was identified as -5×10-3s-1. Stage-two is conducted at relatively low strain rate in order to utilize the fine grains refined by DRX during stage-one to make the grain boundary sliding operate more smoothly, which resulting in enhanced superplastic elongation from 350% to 440%.     

Ti-6Al-4V等离子弧焊对接板超塑胀形特性研究

通过自由胀形实验研究了等离子弧焊对接板的超塑胀形性能及影响因素．结果表明等离子弧焊对接板具有良好的超塑胀形性能，其极限胀形高度可超过凹模半径．在胀形过程中，焊缝组织发展成球状α 长条状α组织．焊缝和基体间存在变形不均匀性．在同样的胀形条件下，胀形气压有—最佳数值，气压过大或过小均降低极限胀形高度．最后给出了一个应用等离子弧焊对接板进行超塑胀形的实例．     

锌铝超塑性合金超塑压缩试验研究

对Ｚｎ－２２％Ａｌ超塑性合金进行了等温超塑压缩试验。在相同的温度、变形速率条件下，研究了不同的变形强度与流动应力及硬度，以及在相同的温度、变形程度条件下，不同的变形速率与流动应力等的关系。     

超细晶超高碳钢研究现状及展望

超细晶超高碳钢是国外近年来发展起来的一类新型的、并具有重要发展前景的高性能钢铁材料.在系统总结大量文献资料的基础上,综述国内外近年来超细晶超高碳钢的研究进展,包括制备工艺,微观组织及其影响因素,室温力学性能,超塑性,层状超高碳钢复合材料等,指出今后超细晶超高碳钢研究的发展方向.     

Zn-Al22合金超塑微成形

采用超塑成形工艺研究了细晶超塑Zn-Al22合金的微成形。采用表面带有微槽和微孔两种形式的不锈钢模具,对所选材料进行了微成形性试验,并利用提出的评价方法对其成形进行评价。微挤压试验证明了材料的微成形性。分析了润滑、压力及模具结构对成形的影响。采用SEM对成形件微观形貌进行了分析。     

Study on practical application of a new seismic damper using a Zn–Al alloy with a nanocrystalline microstructure

Superplastic Zn–Al alloy has some excellent properties needed for a seismic damper, such as high ductility, low work hardening and no harmful metal to human health. In addition, superplastic materials with ultra-fined grains exhibit the high-strain-rate superplasticity and/or low-temperature superplasticity. Some investigations were carried out for nano-sized Zn–Al alloy in order to develop a high-performance seismic damper capable of replacing conventional dampers, such as low-yield-point steel. First, the design for appropriate structure as a damping device using superplastic Zn–Al alloy was discussed by FEM analysis. Secondly, a bulk Zn–Al alloy with nanocrystalline microstructure was manufactured by thermo-mechanical controlling process (TMCP) technology, and the tensile properties of this alloy were compared with that of low-yield-point steel. Then, the full-size cyclic testing of the damping device was carried out in order to evaluate the response for earthquake. As a result, an ecological and high performance seismic damper, the so-called “maintenance-free seismic damper”, has been successfully developed and put into actual use in a high-rise building.