A Fundamental Study of Flow Processes in High-Pressure Torsion

技术总结通过应用严重塑性变形对金属进行加工，为实现特殊的晶粒细化提供了机会。在高压扭转(HPT)中，当圆盘承受压力和同时的扭转应变时，将金属合金的晶粒度减小到纳米范围(100 Nm)通常是可行的。这些超细晶材料表现出非常高的强度和在超塑性成形过程中使用的潜力。将进行实验，以解决HPT处理中的四个主要问题。首先，将评估使用HPT获得完全均匀的微观结构所需的实验参数。其次，将从实验和理论两个方面研究决定HPT中所获得的平衡晶粒度的因素。第三，将调查在HPT处理的材料中报告的异常流动模式的起源，包括涡流和漩涡的存在。第四，HPT将与表面机械磨损处理(SMAT)相结合，以评估生产在工业应用中有相当大用途的硬化盘的机会。非技术总结多晶金属的晶粒度是一个关键参数，因为它决定了强度和流动特性等基本性能。高压扭转(HPT)金属加工是一种相对较新的工艺，它为生产极小晶粒度的块体金属提供了机会。这些金属具有非常高的强度，还表现出其他吸引人的特性，如优异的成形性和良好的耐磨性。这项拟议的研究旨在调查HPT加工技术的一些基本性质，目的是优化该技术，使其能够用于生产工业应用中感兴趣的材料。研究小组将包括一名博士后研究员和至少一名学生，他们将有机会参加一项重大而重要的研究活动。我们还将与日本、巴西和欧洲的几个国际组织合作，这将为学生提供国际体验。

TECHNICAL SUMMARYThe processing of metals through the application of severe plastic deformation provides an opportunity for achieving exceptional grain refinement. In high-pressure torsion (HPT), where a disk is subjected to a pressure and concurrent torsional straining, it is often feasible to reduce the grain size of a metallic alloy to the nanometer range (100 nm). These ultrafine-grained materials exhibit very high strength and a potential for use in superplastic forming processes. Experiments will be conducted to address four major issues in HPT processing. First, experimental parameters that are needed to achieve a fully homogeneous microstructure using HPT will be evaluated. Second, both experimental and theoretical factors that determine the equilibrium grain sizes achieved in HPT will be investigated. Third, the origin of unusual flow patterns, including the presence of swirls and vortices, that have been reported in materials processed by HPT will be investigated. Fourth, HPT will be combined with a surface mechanical attrition treatment (SMAT) to evaluate the opportunity for producing hardened disks that will have considerable use in industrial applications.NON-TECHNICAL SUMMARYThe grain size of a polycrystalline metal is a critical parameter because it determines fundamental properties such as strength and flow characteristics. The processing of metals by high-pressure torsion (HPT) is a relatively new procedure that provides an opportunity for producing bulk metals with extremely small grain sizes. These metals have a very high strength and also exhibit other attractive properties such as excellent formability and good wear resistance. The proposed research is designed to investigate some of the fundamental properties of the HPT processing technique with the objective of optimizing the technique so that it can be used to produce materials of interest for industrial applications. The research group will contain one post-doctoral fellow and at least one student, and they will have an opportunity to participate in a major and important research activity. We will also collaborate with several international groups in Japan, Brazil and Europe, and this will provide the students with an international experience.