Fabrication of light weight materials having ultrafine grain structure through friction stir processing

采用搅拌摩擦工艺（FRP）对铸造铝合金ADC 12和变形铝合金A5083进行了晶粒细化。用普通铣床进行加工。实验研究了两种合金未经特殊预处理的薄板FSP试样及其组织与性能的关系。结果表明：1）FSP工艺的最佳工艺条件是不产生三维缺陷，2）FSP处理后的合金组织均由细小的等轴晶组成，平均晶粒直径为几μ m; 3）FSP处理后的合金晶粒直径均随FSP处理次数的减少而减小;结果表明，经FSP处理后，ADC 12合金的室温力学性能与母材相当接近。6）经FSP处理后，ADC 12合金的铸态试样在高温下的超塑性延伸率大于500%，可能是由于FSP带来的细晶粒结构

Friction stir processing (FRP) has been exploited to cast aluminum alloy ADC12 and wrought aluminum alloy A5083 in order to refine the grain diameter. The processing was performed with an ordinary milling machine. A sheet specimen of both alloys subjected to FSP without any special pretreatment and its microstructure-property relationship was experimentally examined. The results are summarized as follows1) The optimum condition for FSP under which no 3-D defects are formed, was determined as a revolution speed of 985rpm and transition speed of 88mm/min for both alloys2) FSP brought about a microstructure consisting of fine and equi-axed grains with an average diameter of several μm3) The grain diameter tended to decrease with decrease in the number of FSP for both alloys4) Large plate-like phase of silicon in the starting material of ADC12 alloy changed to a number of uniform and spheroidal particles of several μm in diameter5) FSPed specimens showed the mechanical properties at room temperature considerably close to those of parent material6) Cast alloy specimen of alloy ADC12 subjected to FSP showed superplastic elongation larger than 500% at high temperature, probably due to the fine grain structure brought about by FSP