Microstructural Design of Mg Alloys for Lightweight Structural Applications

Energy efficiency and decreasing emission of greenhouse gasses emerge that the importance of Mg alloys. Mg alloys can begin to supersede the steel and aluminum for structural applications, thanks to the developing of mechanical properties or corrosion resistance of Mg alloys. Rare earth metals such as Gd, Ce, Y and Nd have been utilized at AZ31 Mg alloys for this purpose in recent years. In this study, the effects of La addition and homogenization heat treatment on microstructure, hardness properties and corrosion resistance of AZ31 and modified AZ31 Mg alloys produced by low pressure die casting method were investigated.

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Strip Casting and Processing of Al-Mg Alloys for Automotive Structural Applications

Materials Science Forum ◽

10.4028/www.scientific.net/msf.396-402.95 ◽

2002 ◽

Vol 396-402 ◽

pp. 95-100 ◽

Cited By ~ 8

Author(s):

Mark Gallerneault ◽

David J. Lloyd

Keyword(s):

Strip Casting ◽

Mg Alloys ◽

Structural Applications ◽

Al Mg Alloys

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Submicron-grained multiphase TiAlSi alloys: Processing, characterization, and microstructural design

Journal of Materials Research ◽

10.1557/jmr.2001.0254 ◽

2001 ◽

Vol 16 (6) ◽

pp. 1850-1861 ◽

Cited By ~ 5

Author(s):

R. Bohn ◽

G. Fanta ◽

T. Klassen ◽

R. Bormann

Keyword(s):

High Temperature ◽

Silicon Content ◽

Amorphous State ◽

Milled Powder ◽

Decomposition Reaction ◽

High Energy ◽

Grain Sizes ◽

Prepared State ◽

Structural Applications ◽

Microstructural Design

Prealloyed powders of the intermetallic γ–TiAl phase and the ceramic Ξ–Ti5Si3 phase were high-energy milled and hot-isostatically pressed (HIP) to produce silicide dispersed composite materials with grain sizes in the submicron and nanometer range. The amorphous state of the as-milled powders crystallizes via a multistep decomposition reaction during degassing at 440 °C and HIP. At a pressure of 200 Mpa HIP-temperatures as low as 750 °C are sufficient for a complete densification of the milled powder. The microstructure of the compacts is very homogeneous and consists of equiaxed γ–TiAl crystals and Ξ–Ti5(Si,Al)3 particles. Depending on the silicon content, these particles are interspersed within the grain boundary network of the γ–TiAl phase or dispersed inside the γ grains. With respect to technical applications, submicron-grained composites are regarded as promising precursor materials that should allow for easy hot working in the as-prepared state as well as for high-temperature structural applications after a suitable transformation of the microstructure.

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Lattice Imaging of Grain Boundaries in Ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078171 ◽

1977 ◽

Vol 35 ◽

pp. 114-115

Author(s):

D. R. Clarke ◽

G. Thomas

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Silicon Nitride ◽

Grain Boundaries ◽

High Temperature Strength ◽

Current Interest ◽

Lattice Imaging ◽

Special Significance ◽

Structural Applications ◽

Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

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Precipitation in Al-Li-Cu Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096941 ◽

1981 ◽

Vol 39 ◽

pp. 44-45

Author(s):

J. E. O'Neal ◽

K. K. Sankaran

Keyword(s):

Electron Microscopy ◽

Age Hardening ◽

Precipitation Behavior ◽

Zone Formation ◽

Specific Strength ◽

Hardening Behavior ◽

Cu Alloys ◽

High Specific Strength ◽

Transmission Electron ◽

Structural Applications

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.

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A Tem Study of Slip Systems in MoSi2/WSi2 Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089020 ◽

1991 ◽

Vol 49 ◽

pp. 942-943

Author(s):

Stuart A. Maloy

Keyword(s):

Solid Solution ◽

Solid Solution Hardening ◽

Slip Systems ◽

High Melting ◽

Group 14 ◽

Solution Hardening ◽

Brittle To Ductile Transition ◽

High Melting Temperature ◽

Tetragonal Unit Cell ◽

Structural Applications

MoSi2 has recently been investigated as a potential material for high temperature structural applications. It has excellent oxidation resistance up to 1700°C, a high melting temperature, 2030°C, and a brittle-to-ductile transition temperature at 900-1000°C. WSi2 is isomorphous with MoSi2 and has a body-centered tetragonal unit cell of the space group 14/mmm. The lattice parameters are a=3.20 Å and c=7.84 Å for MoSi2 and a=3.21 Å and c=7.88 Å for WSi2. Therefore, WSi2 was added to MoSi2 to improve its strength via solid solution hardening. The purpose of this study was to investigate the slip systems in polycrystalline MoSi2/WSi2 alloys.

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