Production and mechanical properties of Al2O3 particle-reinforced 2024 aluminium alloy composites

Abrasive wear of aluminium composites—a review

Abrasive wear of Al2O3-reinforced aluminium-based MMCs

Metal-matrix composite coatings by PTA surfacing

The wear behavior of unreinforced and reinforced 7091 Al, the latter containing either 20 vol.% SiC particulates (SiC p ) or 20 vol.% SiC whiskers (SiC w ), was studied as a function of sliding distance and sliding velocity under unlubricated conditions. At sliding velocities below 1.2 m s −1 , SiC reinforcement does not affect wear resistance. Wear debris produced from both the unreinforced and reinforced materials was predominantly metallic and was small in dimension and dark in color. The mechanism of wear under these conditions was surface-fatigue-related surface cracking. At sliding velocities greater than 1.2 m s −1 , the wear rates of the reinforced materials were lower than for the unreinforced matrix. Both the unreinforced alloy and the SiC-reinforced composites exhibited elevated wear rates during the initial period of sliding, the mechanism of wear under these conditions, i.e high velocity and short sliding distance, being controlled by subsurface-cracking-assisted adhesive transfer and by abrasion. During steady state sliding, these elevated wear rates were maintained by the unreinforced alloy, reduced wear rates being observed in the reinforced composites. The initial wear rates of the composites depend strongly upon reinforcement orientation, the highest wear rates being observed the perpendicularly oriented SiC w composite. However, the steady state wear rates of the composites were generally independent of reinforcement geometry (particulate vs. whiskers) and orientation (perpendicular vs. parallel) with the exception of wear at 3.6 m s −1 where the parallel-oriented SiC w composite was superior.

Transition wear behavior of SiC-particulate- and SiC-whisker-reinforced 7091 Al metal matrix composites

Composites made with Al–7 wt-%Si alloys and discontinuous Nicalon SiC fibres were prepared by compocasting followed by squeeze casting. This technique gives rise to macroscopically homogeneous materials with, however, some segregation of the fibres in the eutectic phase, especially for the lowest volume fractions. The SiC fibres appreciably improve wear resistance, hardness, and compressive strength of the matrix, both in the as cast and heat treated conditions. An analysis of the compressive test results is given based on the mixture rule modified to apply for discontinuous randomly oriented fibre composites. However, it is shown that agreement between predictions and experimental results can only be obtained by considering the increase of the strength of the matrix as a result of the presence of the fibres. This increase is discussed in terms of structural changes and residual stresses created during cooling resulting from the difference in the coefficients of thermal expansion of the components...

M. Suéry

Papers

Fabrication and properties of metal matrix composites based on SiC fibre reinforced aluminium alloys