Occurrence of HDDR Phenomena and Grain Refinements for Al-Mg Alloys

Abstract

Present paper describes the effects of the Mg content on the occurrence of HDDR phenomena as well as the microstructural evolution in Al-(3-7.8 mass%)Mg alloys. It was found that the HDDR phenomena take place in all those alloys, and grain size of the alloy turned into a several 10 nm after HDDR treatments such as heat-treatment at 350°C under hydrogen pressure of 7.5 MPa for 72 h, in following by the hydrogen desorption treatment at 350°C for 4 h in vacuum. The refined grain size of Al-3.0 mass% Mg alloy was observed to be largest among there alloys. However, it should be emphasized that small content of Mg (3 mass%) is able to induce the HDDR phenomena associated with the nano-order grain refinements in Al-Mg alloys. This could be the first observation of HDDR phenomena which occur in Al-3 and 5 mass% Mg alloys, and are effective for yielding the nano-order fine grain size.