A new class of ultra-hard materials based on AlMgB{sub 14}

Journal Article · Tue Feb 01 04:00:00 EST 2000 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(99)00400-5· OSTI ID:20023186

Cook, B A; Harringa, J L; Lewis, T L; Russell, A M

In this study, aluminum magnesium boride combined with 5 to 30 mol.% additives (AlMgB{sub 14}:X where X = Si, P, C, AlN, TiB{sub 2}, or BN), were prepared by mechanical alloying and consolidated by vacuum hot pressing. Matkovich and Economy first reported the orthorhombic AlMgB{sub 14} intermetallic compound (oI64, space group Imam, a - 0.5848 nm, b = 0.8112 nm, c = 1.0312 nm), and the structure determination was later refined by Higashi and Ito. The unit cell is based on four B{sub 12} icosahedral units centered at (0, 0, 0), (0, 0.5, 0.5), (0.5, 0, 0), and (0.5, 0.5, 0.5) within the unit cell. The remaining eight B atoms lie outside the icosahedra, bonding to the icosahedral B atoms and to the Al and Mg atoms. The Al atoms occupy a four-fold position at (0.250, 0.750, 0.250), and the Mg atoms occupy a four-fold position at (0.250, 0.359, 0). The icosahedra are arranged in distorted, close-packed layers. The unique electronic, optical, and mechanical properties of this material are due to a complex icosahedra (intericosahedral bonding). The highest hardness was observed in the AlMgB{sub 14} + 30%TiB{sub 2} material, which possesses a multi-phase microstructure. Here again, an increase in hardness accompanying the introduction of additional phases is somewhat surprising and difficult to explain. The possible compounds that may form at the AlMgB{sub 14}-TiB{sub 2} interface during hot pressing are numerous.

• Research Organization: Ames Lab., IA (US)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 20023186
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 6 Vol. 42; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM BORIDES
ALUMINIUM NITRIDES
BORON NITRIDES
CARBON
COMPOSITE MATERIALS
CORRELATIONS
HARDNESS
HOT PRESSING
MAGNESIUM BORIDES
MICROSTRUCTURE
PHOSPHORUS
SILICON
TITANIUM BORIDES