Abstract
This paper deals with metal matrix composites (MMCs) of Al 7075 alloy containing different weight percentage (2.5, 5, 7.5, and 10) basalt short fiber reinforcement and unreinforced matrix alloy. The samples were produced by the permanent stir casting technique. The casting ingots were cut into blanks to be forged in single stage and double stage, using MN press and graphite-based lubricant. The microstructures and fatigue properties of the matrix alloy and MMC samples were investigated in the as cast state and in the single and double stage forging operations. The microstructure results showed that the forged sample had a uniform distribution of the basalt short fiber throughout the specimens. Evaluation of the fatigue properties showed that the forged samples had higher values than those of the as cast counterparts. After forging, the enhancement of the fatigue strength of the matrix alloy was so significant and high in the case of 2.5 and 5.0 wt. percentage basalt short fiber reinforced MMC, and there was no enhancement in 7.5 and 10 weight percentages short fiber reinforced MMCs. The fracture damage was mainly due to decohesion at the matrix-fiber interface.
Highlights
Metal matrix composites (MMCs) with better mechanical strength are under development in order to introduce structural components for automotive and aerospace applications, by reducing drastically the weight and increasing the specific strength [1]
The forged microstructure of the Al/10 percentage basalt short fiber composites exhibited some preferential alignment of basalt fiber perpendicular to the forging direction
The basalt short fibers tended to align themselves in such a way that the smallest dimension was parallel to the forging direction
Summary
Metal matrix composites (MMCs) with better mechanical strength are under development in order to introduce structural components for automotive and aerospace applications, by reducing drastically the weight and increasing the specific strength [1]. The particular microstructural changes in MMCs induce stiffness in the direction of fiber to poor transverse direction (transverse direction means perpendicular direction to basalt fiber) due to the weak interface between the matrix and the fiber. The severity of this problem is higher in the case of short fiber reinforced MMCs. On the other hand, as the stiffness and strength are increased, a substantial decrease in ductility is found. Many researchers devoted themselves to the study of the effect of mechanical working such as extrusion [2], rolling [3], and forging [4] on MMCs, and they have shown that some improvements in strength and ductility can be observed with the application of short fiber reinforced Al MMCs [5].
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