首页> 外文学位 >Microstructure and properties of molybdenum disilicide and its composites.
【24h】

Microstructure and properties of molybdenum disilicide and its composites.

机译:二硅化钼及其复合材料的微观结构和性能。

获取原文
获取原文并翻译 | 示例

摘要

Molybdenum disilicide (MoSi2) is a candidate material for high temperature structural applications due to its high melting point and excellent oxidation resistance. A major impediment to implementing this material is its poor room temperature fracture toughness. This study incorporates the microstructure-mechanical property relationship for MoSi2, MoSi 2 alloys, and composites in an effort to determine the feasibility for improving room temperature fracture toughness without undermining the beneficial oxidation and creep properties.; The fracture toughness values reported in the literature vary significantly, and the first part of this study examines the origins for these differences. A diverse array of samples was collected from laboratories involved in exploring MoSi2. These samples were investigated for their microstructural features and indentation response. The non-ideal indentation cracking observed with some MoSi2 samples is based on the anisotropic single crystal properties. The orientation dependency for indentation deformation and fracture was observed for the (110) plane of MoSi2. Fracture toughness values were determined from the damage zone surrounding the indent irrespective of the formation of the ideal radial/median cracking system. Adjustments to fracture toughness values are made to account for the elastic/plastic response. Results from this study indicate that a finely dispersed secondary phase enhances tortuous crack paths and microcracking.; The indentation analysis used for MoSi2 was also applied to MoSi2-Al2O3 and MoSi2-SiC samples. The Al2O3 addition increases the dihedral wetting angles of the triple junction SiO2 in MoSi2 and retards grain growth. These microstructural changes result in differences in the indentation cracking behavior. The fracture toughness improvement for the hot-pressed MoSi2-SiC sample, which is confirmed by four-point bend tests, may be attributed to higher residual stresses that aid in the tortuous crack behavior. Alloying approaches using Al, Ti, or Re to improve fracture toughness met with limited success. The crystal structure changes, lattice spacing modifications, and second phase additions were not helpful in preventing crack propagation.; In addition, isothermal oxidation results of MoSi2 indicate a microstructural effect on the rates of oxidation. The oxidation kinetics are temperature dependent, changing from linear to parabolic at 500°C, and this change is attributed to the volatization of MoO3.
机译:由于其高熔点和优异的抗氧化性,二硅化钼(MoSi2)是用于高温结构应用的候选材料。实施该材料的主要障碍是其差的室温断裂韧性。这项研究结合了MoSi2,MoSi 2合金和复合材料的微观结构-机械性能关系,以试图确定在不损害有益的氧化和蠕变性能的情况下提高室温断裂韧性的可行性。文献中报道的断裂韧性值差异很大,本研究的第一部分检查了这些差异的成因。从参与探索MoSi2的实验室收集了各种样品。研究了这些样品的微观结构特征和压痕响应。在某些MoSi2样品中观察到的非理想压痕裂纹是基于各向异性的单晶特性。在MoSi2的(110)平面上观察到压痕变形和断裂的取向依赖性。断裂韧性值是从凹痕周围的损坏区域确定的,与理想的径向/中部裂纹系统的形成无关。调整断裂韧性值以考虑弹性/塑性响应。这项研究的结果表明,细分散的第二相增强了曲折的裂纹路径和微裂纹。用于MoSi2的压痕分析也适用于MoSi2-Al2O3和MoSi2-SiC样品。 Al2O3的添加增加了MoSi2中三结SiO2的二面角润湿角并阻碍了晶粒长大。这些微观结构变化导致压痕裂纹行为的差异。通过四点弯曲试验证实的热压MoSi2-SiC样品的断裂韧性得到了改善,这可能归因于较高的残余应力,这有助于弯曲的裂纹行为。使用Al,Ti或Re改善断裂韧性的合金化方法获得的成功有限。晶体结构的变化,晶格间距的改变和第二相的添加对防止裂纹扩展没有帮助。另外,MoSi 2的等温氧化结果表明了对氧化速率的微观结构影响。氧化动力学与温度有关,在500°C时从线性变化为抛物线,并且这种变化归因于MoO3的挥发。

著录项

  • 作者

    Newman, Aron English.;

  • 作者单位

    State University of New York at Stony Brook.;

  • 授予单位 State University of New York at Stony Brook.;
  • 学科 Applied Mechanics.; Engineering Metallurgy.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 122 p.
  • 总页数 122
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 应用力学;冶金工业;工程材料学;
  • 关键词

  • 入库时间 2022-08-17 11:48:27

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