Hot workability of nanocrystalline AZ91 magnesium alloy

• Published in: Journal of alloys and compounds Vol. 595; pp. 1 - 7
• Main Authors: Jabbari-Taleghani, M.A., Torralba, J.M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15-05-2014; Elsevier
• Subjects: Alloys; Compressibility (powder); Condensed matter: structure, mechanical and thermal properties; Crystallites; Deformation; Exact sciences and technology; Hot compression test; Hot deformation behavior; Hot pressing; Magnesium base alloys; Mechanical and acoustical properties of condensed matter; Mechanical milling; Mechanical properties of nanoscale materials; Nanocrystalline magnesium alloys; Nanocrystals; Physics; Processing map; Strain; Workability; Workability; Hot compression test; Processing map; Mechanical milling; Nanocrystalline magnesium alloys; Hot deformation behavior; Hot deformation; Plastic flow; Compressive testing; Hardness; Mechanical alloying; Magnesium base alloys; Powder compaction; True stress true strain curve; Nanocrystal; Flow stress; Strain rate
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.01.091

•Nanocrystalline AZ91Mg alloy (grain size 25nm) was prepared by mechanical milling.•Hot workability of the processed nanocrystalline alloy was examined by hot compression tests.•Processing maps for nanocrystalline alloy were developed at strains of 0.1, 0.5, and 0.8.•Nanocrystalline alloy shows excellent workability at high strain rates and moderate temperatures.
This study examined the hot deformation behavior and workability characteristics of nanocrystalline AZ91Mg alloy by performing hot compression tests with a Gleeble-3800 machine. To this end, a nanocrystalline alloy powder with a crystallite size of 25nm was synthesized via mechanical milling of a pre-alloyed AZ91Mg alloy powder for 14h. The mechanically milled (MM) AZ91 powder was subsequently cold pressed at 600MPa into cylindrical compacts measuring 10mm in diameter and 12mm in height. Then, the powder compacts with a relative green density of 91% were hot-compressed at temperatures ranging from 150°C to 500°C and at true strain rates ranging from 0.001s−1 to 10s−1.The true stress–true strain curves peaked at low strains, after which the flow stress increased moderately. Processing maps were developed for all of the hot compression tests at strains of 0.1, 0.5, and 0.8, which represented a safe deformation domain at deformation temperatures and strain rates in the ranges of 250–350°C and 0.1–10s−1. The crystallite size of the nanocrystalline AZ91Mg alloy hot-compressed within the aforementioned domain was measured to be 140nm, which is considered very fine for Mg alloys and resulted in a high hardness value of 133HV for the hot-compressed alloy.