U.S.-Japan Cooperative Science: Development of Materials with Ultra-Fine Grain Sizes

9602919兰登该奖项支持洛杉矶南加州大学的特伦斯·G·兰登教授和日本九州大学的Nemoto教授之间为期三年的合作研究项目。本研究研究了与超细晶材料相关的工艺参数和显微组织特征，包括显微组织和同时发生的组织演变对材料高温力学性能的影响。本研究采用一种新的加工方法“等通道转角挤压(ECA)”来制备纳米晶金属和镁合金。过去的实验已经证明，超细晶粒尺寸在纳米范围内的金属合金在相对较低的温度下具有高延展性和超塑性流动的潜力。ECA提供了一种产生强烈塑性应变的能力，可以将金属合金的晶粒度细化到纳米范围。选择铝和铝基合金以及铜和镁合金进行研究，是因为这种选择可以评估层错能的作用及其对位错网络和晶界结构的影响。这一合作将促进美国人在机械测试方面的广泛专业知识，以及日本人在微观结构分析方面的丰富经验。该研究可能为纳米晶材料的变形加工提供一种新的加工技术，并可能对金属成形行业中未来的金属合金加工产生影响。通过思想和技术的交流，这个项目将扩大我们的基础知识基础，促进国际理解与合作。***

9602919 Langdon This award supports a three-year collaborative research project between Professor Terence G. Langdon of the University of Southern California in Los Angeles and Professor Minoru Nemoto of Kyushu University in Japan. This research investigates processing parameters and microstructural characteristics that are associated with ultrafine grained materials, including the influence of microstructure and concurrent microstructural evolution on the mechanical properties of materials at elevated temperatures. The research employs a new processing method "equal channel angular pressing (ECA)" to create nanocrystalline metal and magnesium alloys. Past experiments have established that metallic alloys with ultrafine grain sizes in the nanometer range have the potential for high ductilities and superplastic-like flow at relatively low temperatures. ECA provides a capability for producing intense plastic straining that can refine the metal alloy grain size into the nanometer range. Aluminum and aluminum-based alloys and copper and magnesium alloys are selected for the study because this selection allows an evaluation of the role of stacking fault energy and its effects on dislocation networks and grain boundary structure. This collaboration will facilitate the extensive expertise in mechanical testing of the Americans with the considerable experience in microstructural analysis of the Japanese. The research could lead to a new processing technique for deformation processing of nanocrystalline materials and could impact future metal alloy processing in the metal forming industries. Through the exchange of ideas and technology, this project will broaden our base of basic knowledge and promote international understanding and cooperation. ***