The present paper describes the grain size refinements of Mg alloys (AZ61, AZ91, ZK60) by HDDR treatment. As a result of the HDDR treatment at 350°C under a hydrogen pressure of 7 MPa for 24 h, following by evacuation at 350°C for 3 h, the grain size of AZ61 alloys was reduced from 10∼20 μm to 100∼200 nm. At the hydrogenation stage for the AZ91 alloys, the disproportionation reaction occurred with forming MgH2, Mg 2Al3 and Al phases. At the following desorption stage, the three phases were recombined and the Mg-Al-Zn solid-solution alloy was reformed. After the HDDR treatment, the grain size of AZ91 alloys was reduced to 100∼200 nm. For the ZK60 alloy without Al, the grain size was reduced from 2∼20μm to about 300 nm by the HDDR treatment.
- Gas-solid reaction
- Grain size refinement
- Hydrogenation disproprotionation desorption recombination phenomena
- Magnesium alloy