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Effects of chemistry on toughness and temperature on structural evolution in metallic glasses.

机译：化学对韧性和温度的影响对金属玻璃的结构演变。

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摘要

The notch toughness of various Bulk Metallic Glasses (BMGs) were investigated. Systematic changes in composition to change the Poisson's ratio were employed to increase the notch toughness of a variety of Fe-BMGs. The Fe 50Mn10Mo14Cr4C16B6 BMG possessed very high hardness (e.g. 12 GPa) but very low notch toughness (e.g. 5.7MPam1/2) at room temperature, consistent with fracture surface observations of brittle features. Many of the other Fe-BMG variants, created to change the Poisson's ratio, exhibited higher toughness but more scatter in the data, reflected in a lower Weibull modulus. SEM examination revealed fracture initiation always occurred at inclusions in samples exhibiting lower toughness and/or Weibull modulus for a given chemistry. Implications of these observations on reliability of BMGs are presented. In addition, high-temperature micro-hardness testing on fully amorphous Fe48Mo14Cr 15Y2C15B6 was performed in order to determine the behavior and structure evolution under a variety test conditions. The effects of changes in test temperature on the micro-hardness/strength were determined over the temperature range from 25°C to 620°C. Although high (e.g., > 12 GPa) micro-hardness was exhibited at 25°C, significant hardness reductions were exhibited near Tg. In addition, the effect of exposure time (up to 300 minutes) at elevated temperature on the evolution of micro-hardness/strength was also evaluated for selected temperatures between 25°C and 620°C. The micro-hardness results were complemented with X-ray diffraction (XRD), conventional transmission electron microscopy (TEM), and an in-situ heating TEM study in order to evaluate any structural evolution that could explain the large differences in hardness evolution under different test conditions.
机译：研究了各种块状金属玻璃（BMG）的缺口韧性。系统地改变组成以改变泊松比，以增加各种Fe-BMG的缺口韧性。 Fe 50Mn10Mo14Cr4C16B6 BMG在室温下具有非常高的硬度（例如12 GPa），但是缺口韧性非常低（例如5.7MPam1 / 2），这与断裂表面的脆性观察一致。为改变泊​​松比而创建的许多其他Fe-BMG变体表现出更高的韧性，但数据分散性更高，反映出较低的威布尔模量。 SEM检查显示，对于给定的化学性质，样品中的夹杂物总是发生断裂起始，表现出较低的韧性和/或威布尔模量。这些意见对BMG的可靠性提出了建议。另外，为了确定在各种测试条件下的行为和结构演变，对完全非晶态的Fe48Mo14Cr 15Y2C15B6进行了高温显微硬度测试。在25°C至620°C的温度范围内确定了测试温度变化对显微硬度/强度的影响。尽管在25℃下表现出高（例如＞ 12GPa）的显微硬度，但是在Tg附近表现出显着的硬度降低。此外，还针对25°C至620°C之间的选定温度评估了高温下的暴露时间（最长300分钟）对显微硬度/强度演变的影响。显微硬度结果与X射线衍射（XRD），常规透射电子显微镜（TEM）和原位加热TEM研究相辅相成，以便评估可以解释不同条件下硬度变化的巨大差异的任何结构演变测试条件。

著录项

  • 作者

    Shamimi Nouri, Ali.;

  • 作者单位

    Case Western Reserve University.;

  • 授予单位 Case Western Reserve University.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 200 p.
  • 总页数 200
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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