Alloy Matrix Material Research Articles

Additivity of reinforcing mechanisms during creep of metal matrix composites: Role of the microstructure and the processing route

During decades, great efforts have been devoted to understand and predict the creep behavior of discontinuously reinforced metal matrix composites, particularly aluminum alloy matrix materials. As a result of all these investigations, however, a confuse panorama of the precise role of the reinforcing particles on the enhanced creep response of these materials rules the present understanding. Here, an analysis of the reasons that have driven to this situation is made. Also, a simple and generalized framework of the relevant mechanisms required to understand this behavior is proposed. This view is based on previous work by these authors on 6061Al alloy, prepared by ingot and powder metallurgy, and 6061Al–15 vol.% SiC w composite, as well as a data analysis of published investigations aimed at clarifying the above situation. The additivity of the proposed contributions and the potential damage mechanism are discussed in the context of the processing route employed.

Thermal spraying of billets and fiber prepregs for semi-solid forming of metal matrix composites

The use of thermal spray processes with subsequent material densification by semi-solid forming can yield advantages for manufacturing of metal matrix composites (MMC) compared to well-established manufacturing methods like spray forming or diffusion bonding. The main challenges of this method lie in well defined process temperatures during material deposition and forming, handling of the material during the processes, microstructure of the semi-finished matrix, and economical efficiency of the process chain. Particulate reinforcement of light metal matrix material is mainly aimed on improvement of mechanical properties at elevated temperatures, e.g. wear behavior, creep resistance, yield and tensile strength. Composite formation for particle reinforced metals (PRM) by thermal spraying with the arc wire system is achieved by simultaneous deposition of matrix and reinforcement by means of cored wires. Unidirectional (UD) fiber reinforced MMC yield highest specific mechanical properties and can be processed by winding of a continuous fiber strand and coating of the fiber layer by arc wire spraying with wires from light alloy matrix material or by plasma spraying with mixed powders. The coating process can be simultaneous to the winding process or in a separate step for prepreg manufacturing with shape and fiber content adapted to the final component geometry and load case.

Adhesive wear behaviour of B 4C and SiC reinforced 4147 Al matrix composites (Al/B 4C–Al/SiC)

Adhesive wear characteristics of 4147 Al/B 4C, 10, 15 and 20 wt.% B 4C particle and Al/SiC metal matrix composites 20 wt.% SiC contain produced by liquid metallurgy have been investigated under the dry sliding conditions and their wear behaviours are compared with 4147 Al/SiC-reinforced 20 wt.% SiC. The results showed that the wear resistance of Al/B 4C matrix increases considerably with increasing wt.% B 4C particle content in Al alloy matrix. When Al alloy matrix material is in severe adhesive-abrasive wear, the Al/B 4C composites are in light-mild adhesive wear stage at the same wear condition. B 4C content and its behaviour in Al matrix is determined factor for wear rate and mechanism of the MMC. The relationship between the wear resistance and wear mechanism is also observed, and it depends on soakabality of B 4C particle by the matrix. When Al/B 4C wear behaviour is compared with Al/SiC MMC, Al/SiC wear resist is high, and the worn sample of Al/SiC only shows a light adhesive wear traces at the same conditions.

Influence of Processing Variables on the Corrosion Susceptibility of Metal-Matrix Composites

Abstract Metal-matrix composites (MMC) suffer from preferential corrosion because of their nonhomogeneous composition and structure. In particular, aluminum alloy matrix materials are very suscepti...

The tensile failure modes of metal-matrix composite materials

T he strengths of individual boron fibers extracted from various as-received and thermally-fatigued aluminum alloy matrix materials were measured. The results are described in terms of a Weibull distribution, and strengths of composites fabricated from these fibres are calculated in terms of lower and upper bounds. Tests conducted on composites specimens indicated that strengths approaching the upper bounds can be achieved in composites fabricated by normal diffusion bonding techniques. Cyclic temperature changes effectively reduced the strength values towards the lower bounds. It was concluded that this effect resulted from the degradation of the strength of the fiber-matrix bond.