Particulate Metal Matrix Research Articles

Strengthening of a particulate metal matrix composite by quenching

The strengthening of a particulate metal matrix composite due to quenching was studied both experimentally and theoretically. The strengthening was attributed to two mechanisms: punched-out dislocations due to CTE mismatch strain and back stress. Both mechanisms were analyzed by theoretical modeling leading to a good agreement between the experimentally observed strengthening and the prediction by the models. A parametric study revealed that the volume fraction of particulate, quenching temperature and its temperature differential and particulate size are the major variables influencing the increase in composite flow stress.

Statistical analysis of particulate interface lengths in diffusion bonded joints in a metal-matrix composite

A statistical analysis has been made of the number and length of particle-particle (P-P), particle-matrix (P-M) and matrix matrix (M-M) interfaces present in solid state and liquid phase diffusion bonded joints in a particulate metal matrix composite (17 vol % SiC/Al-Li 8090 alloy). All solid state bonds had planar bond interfaces with the polished particle facets aligned in and parallel to the bond interface. The particle interface lengths in 400 μm long sample lengths in the L direction in a bond interface could vary from zero to over 50% of the sample length, with typical values for a random sample of 8% and 22% for P-P and P-M interfaces, respectively.

Strengthening mechanisms in particulate metal matrix composites

Strengthening mechanisms in particulate metal matrix composites

GROWTH OF FATIGUE CRACKS EMANATING FROM NOTCHES IN SiC PARTICULATE ALUMINUM COMPOSITE

Abstract— The initiation and growth of cracks emanating from blunt notches in 6061‐Al alloy reinforced with 25% particulate Sic metal matrix composite were investigated. To elucidate the role of aging condition of the matrix on the fatigue behavior, the studies were carried out at T6 and overaged conditions. The results show that the number of cycles required for initiation of fatigue cracks are not influenced with the notch severity and the aging condition of the matrix. The overaging heat treatment resulted in slower fatigue crack growth rates. The failure of the Sic particles during the fatigue process is given as the reason for the both observed initiation and crack growth characteristics. It is also shown that the growth rate of cracks emanating from blunt notches can be accurately described by an equivalent stress intensity factor range ΔKeq. This could provide an adequate engineering method for design against fatigue failure from various stress concentrations for this composite system.

Bauschinger effect in particulate SiC-6061 aluminum composites

The work-hardening behavior of a particulate metal matrix composite (MMC) was studied in terms of the Bauschinger effect. The particulate MMC system used in this study is SiC particulate in 6061 aluminum alloy with three different aging conditions: unaged (solution-treated T4) and T4 aged at 175 °C for 4 and 8 h. The experimental results of the stress-strain behavior of the MMCs, which were processed by the casting route, are considered in terms of the Bauschinger effect, the difference ( Δσ f) and sum ( Σσ f) and of flow stresses in the forward ( σ t f) and backward loading ( σ c f) directions It was found that Δσ f increases linearly with plastic strain ϵ p up to some point ( ϵ b p ) and then bends to a non-linear curve, while the relation between Σσ f and ϵ p gives rise to a flat curve. These results are confirmed by an analytical study based on Eshelby's model. These findings imply that the work hardening of this particulate MMC system is mainly due to back stress and not to forest dislocations or the source-shortening stress effect.

The Strength and Fracture Behaviour of Diffusion Bonded Joints in Al-Li(8090) Alloy Sheet

Solid state and transient liquid phase diffusion bonded joints have been made between Al-Li 8090 alloy and 8090 alloy/SiC particulate metal matrix composite. In this paper some shear and peel strengths are reported and the factors that affect the strength and fracture behaviour are discussed. Comparisons are made with other published data for bonded joints in Al-Li alloys.

Effects of superimposed hydrostatic pressure on the fracture properties of particulate reinforced metal matrix composites

Etude des effets d'une compression hydrostatique et de la microstructure sur le comportement a la deformation et a la rupture d'un alliage d'aluminium renforce par des particules de carbure de silicium (15% en volume), soumis a un essai de traction. Analyse par microscopie electronique a balayage des surfaces de rupture

TEM examination of 2014-SiC metal matrix composite

Aluminum-based metal matrix composites offer unique combinations of high specific strength and high stiffness. The improvement in strength and stiffness is related to the particulate reinforcement and the particular matrix alloy chosen. In this way, the metal matrix composite can be tailored for specific materials applications. The microstructural characterization of metal matrix composites is thus important in the development of these materials. In this study, the structure of a p/m 2014-SiC particulate metal matrix composite has been examined after extrusion and tensile deformation.Thin-foil specimens of the 2014-20 vol.% SiCp metal matrix composite were prepared by dimpling to approximately 35 μm prior to ion-milling using a Gatan Dual Ion Mill equipped with a cold stage. These samples were then examined in a Philips 400T TEM/STEM operated at 120 kV. Two material conditions were evaluated: after extrusion (80:1); and after tensile deformation at 250°C.

Fractography of a SiC particulate reinforced aluminium metal matrix composite

Etude par microscopie electronique a balayage des materiaux a matrice metallique d'alliage Al-6061 renforces par SiC rompus par traction. Analyse et comprehension du mecanisme de rupture