High-strengthening of Mg - 5.5 mass % Y-4.3 mass % Zn cast alloy by friction stir processing

Abstract

High-strength Mg-Y-Zn alloy plate was obtained by friction stir processing (FSP) after casting. In this study, the Mg-Y-Zn alloy by FSP showed sufficiently high performance with low cost. As-cast material was held at 723 K for 95 h. It then showed a lamellar structure, which might have resulted from long-range periodic structure. However, this lamellar structure showed very low hardness, as did the as-cast material. Plates cut from heat-treated ingot were processed as single, overlapped double, and multiple pass FSP. After FSP, each processed materials was cut for microscopic measurement and hardness testing. Ultra-fine-grained microstructures are obtainable using the FSP. Micro-Vickers hardness tests for each pass result in the occurrence of strengthening for FSP of Mg-Y-Zn alloy. There was little change in grain size and hardness of prestirred zone by the next pass of stirring. ©2005 The Japan Institute of Metals.