Professor James Economy's Group

[Carbon/BN Composite] [AlB2 Composite] [Polymer Composites]

Aluminum / Aluminum Diboride Metal Matrix Composites

In-situ aluminum matrix composites based on the aluminum-copper-boron ternary system have been developed for the first time. Aluminum diboride, one of many stable crystalline phases naturally present in the alloy system, is exploited as a reinforcement. AlB₂ exists in the aluminum matrix as single crystal high aspect ratio flakes. Proper heat treatment allows for the preparation of an aluminum composite containing only this phase. Reinforcement volume fraction can be varied from 0 to 20% by control of alloy composition and by the use of a modified squeeze casting apparatus. At 20v/o loading of AlB₂ an 80% increase in strength over the matrix alloy is observed. Wear and creep resistance of these composites is also found to be excellent.

Current research is focusing on the following areas:

Redtermination of the Al-B phase diagram.

Considerable disagreement exists in the literature concering the Al_(L) + AlB₂ -> Al_(L) + AlB₁₂ peritectic transition temperature. Experiments to determine this temperature are underway.

Preparation of AlB₂ MMC's for comodity materials.

Using comodity boron sources we project that 20 % AlB₂ MMC's can be prepared for less than $5/Kg.

Preparation of macroscopic oriented boride structure in aluminum.

Macroscopic structures of oriented borides have been created in aluminum. It is believed that these structures could lead to composites with unique properties.

Selected Micrographs

Figure 1: 20 vol% AlB2 in Aluminum	Figure 2: AlB2 in Aluminum, 55% Copper, Matrix
Figure 3: 15 vol% AlB2 filtered under shear. Partial alignment noticeable.	Figure 4: 30 vol% AlB2 filtered under shear. Al, 3.3%Cu, matrix.
Figure 5: AlB2 prepared using Boron Oxide as a boron source.	Figure 6: AlB2 prepared using Borax as a boron source.

Related Publications

The following is a list of related publications which you may find of interest.

1.      Deppisch, G. Liu, J.K. Shang, and J. Economy; Fabrication of AlB2 Flake Reinforced Al-Alloy Composites

2.      C. Deppisch, G. Liu, J.K. Shang, and J. Economy; Effect of Cooling Rate on the Crystallization of AlB2 Flakes in Al Composites

3.      L. Wohrer, A. Wosilait, and J. Economy; SAMPE 18, 340-68 (1973).

Jacob Lee Meyer