Abstract
Fabrication process and mechanical properties of uniaxially oriented SiC whisker reinforced AA 7001 aluminum alloy composites (FRM) with oriented whisker preform by electrostatic method is described.
In the electrostatic method of fabricating a uniaxially oriented SiC whisker preform, whiskers suspended in an insulating liquid (freon R-113) are oriented in the field direction. To investigate this phenomena, the experimental observation of whisker motion is made using a cell with 3-mm electrode gap, which viewed through a microscope. SiC whiskers are polarized and oriented in both dc and ac (f=12500 Hz) field, showing the time constant of polarization is sufficiently smaller than that of mechanical orientation. SiC whiskers form long agglomerates in the ac field. In the frequency range of 1 to 10 Hz, oriented whisker agglomerates with better orientation are observed.
A fabricated uniaxially oriented preform is incorpolated into an aluminum alloy by squeeze casting. This uniaxially oriented FRM has higher bending strength and fatigue strength than FRM with 3-dimensionally random oriented whiskers. Ratios of the matrix to the uniaxially oriented FRM in the bending strength and the fatigue strength are 2.1 and 4.2 respectively.
