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首页> 外文学位 >Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual Phase Precipitation Hardened Powder Metallurgy Stainless Steels.
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Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual Phase Precipitation Hardened Powder Metallurgy Stainless Steels.

机译：热时效对双相沉淀硬化粉末冶金不锈钢显微组织和力学行为的影响。

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摘要

Increasing demand for high strength powder metallurgy (PM) steels has resulted in the development of dual phase PM steels. In this work, the effects of thermal aging on the microstructure and mechanical behavior of dual phase precipitation hardened powder metallurgy (PM) stainless steels of varying ferrite-martensite content were examined. Quantitative analyses of the inherent porosity and phase fractions were conducted on the steels and no significant differences were noted with respect to aging temperature. Tensile strength, yield strength, and elongation to fracture all increased with increasing aging temperature reaching maxima at 538°C in most cases. Increased strength and decreased ductility were observed in steels of higher martensite content. Nanoindentation of the individual microconstituents was employed to obtain a fundamental understanding of the strengthening contributions. Both the ferrite and martensite hardness values increased with aging temperature and exhibited similar maxima to the bulk tensile properties.;Due to the complex non-uniform stresses and strains associated with conventional nanoindentation, micropillar compression has become an attractive method to probe local mechanical behavior while limiting strain gradients and contributions from surrounding features. In this study, micropillars of ferrite and martensite were fabricated by focused ion beam (FIB) milling of dual phase precipitation hardened powder metallurgy (PM) stainless steels. Compression testing was conducted using a nanoindenter equipped with a flat punch indenter. The stress-strain curves of the individual microconstituents were calculated from the load-displacement curves less the extraneous displacements of the system. Using a rule of mixtures approach in conjunction with porosity corrections, the mechanical properties of ferrite and martensite were combined for comparison to tensile tests of the bulk material, and reasonable agreement was found for the ultimate tensile strength. Micropillar compression experiments of both as sintered and thermally aged material allowed for investigation of the effect of thermal aging.
机译：对高强度粉末冶金（PM）钢的需求不断增长，导致了双相PM钢的发展。在这项工作中，研究了热时效对铁素体-马氏体含量不同的双相沉淀硬化粉末冶金（PM）不锈钢的显微组织和力学行为的影响。对这些钢的固有孔隙率和相分数进行了定量分析，并且在时效温度方面未发现明显差异。在大多数情况下，拉伸强度，屈服强度和断裂伸长率都随着时效温度的升高而增加，达到538°C的最大值。在较高马氏体含量的钢中观察到强度增加和延展性降低。使用单个微成分的纳米压痕获得对增强作用的基本了解。铁素体和马氏体的硬度值都随着时效温度的增加而增加，并显示出与整体拉伸性能相似的最大值。由于与常规纳米压痕相关的复杂的不均匀应力和应变，微柱压缩已成为一种探测局部力学行为的有吸引力的方法限制应变梯度和周围特征的贡献。在这项研究中，通过聚焦离子束（FIB）铣削双相沉淀硬化粉末冶金（PM）不锈钢来制造铁素体和马氏体微柱。使用配备有平冲头的纳米压头进行压缩测试。根据载荷-位移曲线减去系统的无关位移计算出各个微成分的应力-应变曲线。使用混合法则与孔隙率校正相结合，将铁素体和马氏体的力学性能相结合，以与块状材料的拉伸试验进行比较，并找到了合理的一致性，以达到极限拉伸强度。烧结和热老化材料的微柱压缩实验可以研究热老化的影响。

著录项

  • 作者

    Stewart, Jennifer.;

  • 作者单位

    Arizona State University.;

  • 授予单位 Arizona State University.;
  • 学科 Engineering Materials Science.
  • 学位 M.S.
  • 年度 2011
  • 页码 100 p.
  • 总页数 100
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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