Dandliker, Richard B. (1998) Bulk metallic glass matrix composites : processing, microstructure, and application as a kinetic energy penetrator. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-01242008-074925
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The development of alloys with high glass forming ability allows fabrication of bulk samples of amorphous metal. This capability makes these materials available for applications which require significant material thickness in all three dimensions. Superior mechanical properties and advantages in processing make metallic glass a choice candidate as a matrix material for composites. This study reports techniques for making composites by melt-infiltration casting using the alloy [...] ([...]) as a matrix material. Composite rods 5 cm in length and 7 mm in diameter were made and found to have a nearly fully amorphous matrix; there was less than 3 volume percent crystallized matrix material. The samples were reinforced by continuous metal wires, tungsten powder, or silicon carbide particulate preforms. The most easily processed samples were made with uniaxially aligned tungsten and carbon steel continuous wire reinforcement; the majority of the analysis presented is of these samples. The measured porosity was typically less than 3%. The results also indicate necessary guidelines for developing processing techniques for large scale production, new reinforcement materials, and other metallic glass compositions. Analysis of the microstructure of the tungsten wire and steel wire reinforced composites was performed by x-ray diffraction, scanning electron microscopy, scanning Auger microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The most common phase in the crystallized matrix is most likely a Laves phase with the approximate formula [...]. In tungsten-reinforced composites, a crystalline reaction layer 240 nm thick of tungsten nanocrystals in anamorphous matrix formed. In the steel reinforced composites, the reaction layer was primarily composed of a mixed metal carbide, mainly [...]. One promising application of the metallic glass mat composite is as a kinetic energy penetrator material. Ballistic tests show that a composite of 80 volume percent uniaxially aligned tungsten wires and a [...] 1 matrix has self-sharpening behavior, which is a necessary characteristic of superior penetrator materials. Small-scale tests with both aluminum and steel targets show that this composite performs better than tungsten heavy alloys typically used for penetrator applications, and comparably with depleted uranium.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Major Option:||Materials Science|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||24 October 1997|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||15 Feb 2008|
|Last Modified:||26 Dec 2012 02:28|
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