Creep and Superplasticity in Materials with Ultrafine Grain Sizes

超细晶粒材料的蠕变和超塑性

• 批准号: 0243331
• 负责人: Terence Langdon
• 金额: $ 48万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0243331&HistoricalAwards=false
• 关键词: Creep; Superplasticity; Materials; Ultrafine; Grain

The grant investigates processing and characterization of aluminum and magnesium alloys via severe plastic deformation (SPD) using equal channel angular pressing (ECAP). Appropriate dispersion of second phase particles are expected to pin the grain boundaries thereby retaining ultra fine grain size in submicron range. The relatively large range of grain sizes, from micron to nanometers, will provide an opportunity to unambiguously determine the creep and superplastic properties when the grain sizes are extremely small and to obtain fundamental information that will be needed in the longer term for the successful utilization of these materials. A goal of the study is to utilize advanced techniques such as atomic force microscopy to systematically investigate cavitation and grain boundary sliding following ECAP as well as deformation of the processed materials. Along with superplasticity, the underlying mechanisms of diffusional creep will be investigated.From a scientific viewpoint, there are well-developed theories predicting the plastic flow (or creep) of metals when the grain sizes are small but these theories remain open to considerable speculation and there has been much discussion and disagreement concerning their general validity. The study is expected to fill in the gaps and provide scientific understanding of deformation mechanisms at varied grain sizes and in a range of applied stresses and strain-rates. In addition, the investigations will have technological applications for forming operations. The grant avails participation of graduate and post-graduate students along with undergraduate senior projects. The project is co-funded by metals program in the division of materials research and manufacturing in the division of manufacturing and industrial innovation.

该基金研究了铝和镁合金通过等通道转角挤压（ECAP）进行严重塑性变形（SPD）的加工和表征。第二相颗粒的适当分散预期钉扎晶界，从而保持亚微米范围内的超细晶粒尺寸。从微米到纳米的相对较大的晶粒尺寸范围将提供一个机会，当晶粒尺寸非常小时，可以明确地确定蠕变和超塑性性能，并获得长期成功利用这些材料所需的基本信息。研究的一个目标是利用先进的技术，如原子力显微镜，系统地研究ECAP后的空穴和晶界滑动以及加工材料的变形。沿着超塑性，扩散蠕变的基本机制将被研究。从科学的观点来看，当晶粒尺寸很小时，有成熟的理论预测金属的塑性流动（或蠕变），但这些理论仍然是开放的，相当多的猜测，有很多的讨论和分歧，关于它们的普遍有效性。这项研究有望填补空白，并提供科学的理解变形机制在不同的晶粒尺寸和施加的应力和应变率的范围。此外，这些研究还将在成形操作中得到技术应用。该补助金使研究生和研究生沿着参加本科高级项目。该项目由制造和工业创新部门的材料研究和制造部门的金属计划共同资助。