• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Mechanical and tribological properties of ultrafine grained zinc-copper-aluminum alloy obtained by Equal Channel Angular Extrusion.
【24h】

Mechanical and tribological properties of ultrafine grained zinc-copper-aluminum alloy obtained by Equal Channel Angular Extrusion.

机译：等通道角挤压获得的超细晶粒锌铜铝合金的力学和摩擦学性能。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The Zn-9%Al-3%Cu (ZCA-9) alloy was subjected to Equal Channel Angular Extrusion (ECAE) process using two different processing techniques, routes A and BC at 65°C. For route A, the specimens are processed along the extrusion axis without any rotation whereas the specimens are rotated 90° counter-clockwise around its extrusion axis between successive passes for route BC. The influences of the ECAE passes and its routes, on the mechanical properties such as strength, hardness, ductility and damping and the tribological properties such as wear, friction were investigated. The specimens were tested in uniaxial tension, compression, creep, nanoindentation and frequency scan damping tests were conducted to determine the mechanical properties. Wear and nanoscratch tests were also conducted to determine the tribological properties of the as-cast and ECAE processed ZCA-9 alloy. The microstructural features such as grain size, texture and presence of different phases in the as-cast, as-ECAE and post-ECAE aged alloy at the temperature of 160°C and 250°C were correlated with the mechanical properties. An upper bound model was developed to predict the extrusion pressure required during the ECAE process and was compared with experimental results.;Microstructural observations revealed a greatly refined and equiaxed grain structure with the crystallite size between 0.2-0.8 microm in as-cast and the ECAE processed ZCA-9 alloy. After post-ECAE aging of this alloy processed by route BC for 300 hours, the grain sizes were found to be in range of 1.65--1.88 microm at temperature of 160°C and grain sizes between 2.10--3.37 microm at the temperature of 250°C. The grain sizes were found to have increased with increase in number of passes. In the specimens processed by route A, elongated grain structures were observed with agglomerates of Zn-rich and Alrich grains while in route B C specimens, the equiaxed grains were observed.;The ECAE process was found very effective in improving the mechanical properties of ZCA-9 alloy. The mechanical properties were found to vary significantly with the grain size, strain rate and temperature. The ultimate tensile strength (UTS), yield strength (YS), hardness and damping capacity were found to increase after one pass and then gradually decreases with further increase in number of passes, i.e., increase in grain sizes. Aging at temperature of 160°C of the as-cast and ECAE processed specimens showed a slight increase in the UTS, YS and hardness compared to the unaged specimens. However, the as-ECAE processed specimens showed exceptionally high ductility with increase in number of passes compared to the aged specimens. In compression, the YS and the work hardening rate were found to increase with increasing strain rates. The strain hardening exponent was seen to decrease with increase in number of passes. Tension-compression asymmetry in the YS was observed in the as-cast and one pass ECAE processed alloy with asymmetry more in the favor of compression (higher).;The ECAE processed specimens exhibited poor creep resistance and duration to failure compared to the as-cast specimen. This creep resistance of the ECAE processed specimens was seen to deteriorate at a higher testing temperature of 160°C. The wear results demonstrated that the wear resistance of the alloy can be improved with eight ECAE passes of route A. No significant change in the coefficient of friction was observed with change in sliding speeds. The damping capacity of the ZCA-9 alloy was found to decrease with increase in frequency.;The upper bound study shows that there is a good agreement between the theoretical and experimental pressure required to extrude the material through the equal channel angular die.
机译：Zn-9％Al-3％Cu（ZCA-9）合金在65°C下使用两种不同的加工技术（路线A和BC）进行了等通道角挤压（ECAE）工艺。对于路径A，样品在不进行任何旋转的情况下沿挤压轴进行处理，而样品在路径BC的连续遍历之间围绕其挤压轴逆时针旋转90°。研究了ECAE通道及其路径对机械性能（如强度，硬度，延展性和阻尼）的影响，以及摩擦学性能（如磨损，摩擦）。对样品进行了单轴拉伸，压缩，蠕变，纳米压痕和频率扫描阻尼测试，以确定其机械性能。还进行了磨损和纳米划痕试验，以确定铸态和ECAE处理的ZCA-9合金的摩擦学性能。在160°C和250°C的温度下，铸态，as-ECAE和后ECAE时效合金的微观结构特征（例如晶粒尺寸，织构和不同相的存在）与机械性能相关。建立了一个上限模型来预测ECAE过程中所需的挤压压力，并将其与实验结果进行了比较。；显微组织观察显示，铸态和ECAE中的晶粒尺寸在0.2-0.8微米之间，具有非常细化和等轴的晶粒结构加工的ZCA-9合金。在经BC路线处理的该合金的ECAE后老化300小时后，发现在160°C的温度下晶粒尺寸在1.65--1.88微米范围内，在200摄氏度的温度下晶粒尺寸在2.10--3.37微米之间。 250℃。发现晶粒度随着通过次数的增加而增加。在路线A加工的试样中，观察到细长的晶粒结构，富含锌和Alrich晶粒的团聚体，而在路线BC试样中，观察到等轴晶粒。； ECAE工艺对于改善ZCA-的机械性能非常有效。 9合金。发现机械性能随晶粒尺寸，应变速率和温度而显着变化。发现在一次通过后极限抗拉强度（UTS），屈服强度（YS），硬度和阻尼能力增加，然后随着通过次数的进一步增加即晶粒尺寸的增加而逐渐降低。与未老化的试样相比，铸态和ECAE处理的试样在160°C的温度下时效显示UTS，YS和硬度略有增加。但是，与老化后的样品相比，经ECAE处理的样品具有极高的延展性，并且通过次数增加。在压缩中，发现YS和加工硬化率随应变率的增加而增加。观察到应变硬化指数随着通过次数的增加而降低。在铸态和一次通过ECAE处理的合金中观察到YS中的拉伸压缩不对称性，其中不对称性更多地倾向于压缩（更高）。与原始状态相比，ECAE处理的样品表现出较差的抗蠕变性和破坏持续时间-铸造标本。在160°C的较高测试温度下，观察到的经ECAE处理的样品的抗蠕变性降低。磨损结果表明，通过路径A的8次ECAE加工可以改善合金的耐磨性。随着滑动速度的变化，未观察到摩擦系数的显着变化。发现ZCA-9合金的阻尼能力随频率的增加而降低。上限研究表明，通过等通道角模挤压材料所需的理论压力与实验压力之间有很好的一致性。

著录项

  • 作者

    Patil, Akshay G.;

  • 作者单位

    Michigan Technological University.;

  • 授予单位 Michigan Technological University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 207 p.
  • 总页数 207
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号