中文摘要：

提出了一种制备整块、全板厚超细晶板材的强冷摩擦搅拌工艺，利用搅拌头与基材之间摩擦搅拌过程的剧烈塑性变形条件细化金属晶粒，通过搅拌位置的机械移动制备整块的超细晶板材．同时，采用强制冷却方式抑制动态回复和再结晶晶粒的长大，提高晶粒细化效果．建立了该工艺过程中应变速率、应变量及加热功率的数学模型，优化了紫铜板材细晶制备工艺参数，对所制得的细晶材料进行了硬度试验和显徽组织分析．结果表明，增强冷却能减小晶粒尺寸和提高细晶材料的硬度．制备出的超细晶紫铜板材布氏硬度可达HBS100，比退火紫铜的硬度约高一倍．

英文摘要：

The forced cooling friction stir process is found to prepare one-piece and whole thickness ultra fine grain （UFG） plate. As the stir pin rotates with high speed and high pressure, the severe shear plastic deformation zone forms between the stir pin and base metal. The metal grains deformed, broke, and recrystallized. Because of high pressure and lower temperature, the UFG appear at the deformation zone. In order to obtain more fine grain, the forced cooling method was used to restrain the dynamic recovery, recrystallization and grain growth. The mathematic models of strain, strain rate, heating power were built up. The process parameters were optimized to prepare the copper UFG plate. With enhancing the cooling effect, the grain diameters of UFG plate decreased and the hardness increased. The UFG copper plate with average grain diameter of about 0.5-0.7 μm can be obtained, and its Brinell hardness HBS100 is double as the annealed copper.