Formation and mechanism of nanocrystalline AZ91 powders during HDDR processing

Journal Article · Wed Mar 15 04:00:00 EDT 2017 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2017.01.028· OSTI ID:22689729

Liu, Yafen; Fan, Jianfeng; Zhang, Hua; Zhang, Qiang; Gao, Jing; Dong, Hongbiao; Xu, Bingshe

Grain sizes of AZ91 alloy powders were markedly refined to about 15 nm from 100 to 160 μm by an optimized hydrogenation-disproportionation-desorption-recombination (HDDR) process. The effect of temperature, hydrogen pressure and processing time on phase and microstructure evolution of AZ91 alloy powders during HDDR process was investigated systematically by X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy, respectively. The optimal HDDR process for preparing nanocrystalline Mg alloy powders is hydriding at temperature of 350 °C under 4 MPa hydrogen pressure for 12 h and dehydriding at 350 °C for 3 h in vacuum. A modified unreacted core model was introduced to describe the mechanism of grain refinement of during HDDR process. - Highlights: • Grain size of the AZ91 alloy powders was significantly refined from 100 μm to 15 nm. • The optimal HDDR technology for nano Mg alloy powders is obtained. • A modified unreacted core model of grain refinement mechanism was proposed.

• OSTI ID: 22689729
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 125; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRYSTALS
DESORPTION
GRAIN REFINEMENT
GRAIN SIZE
HYDRIDATION
HYDROGEN
HYDROGENATION
MAGNESIUM ALLOYS
NANOSTRUCTURES
OPTICAL MICROSCOPY
OXIDATION
PHASE TRANSFORMATIONS
POWDERS
REDUCTION
SCANNING ELECTRON MICROSCOPY
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION