Metal matrix composites consist of a metal or an alloy as the continuous matrix and a reinforcement that can be particle, short fiber or whisker, or continuous fiber. In this chapter, we first describe important techniques to process metal matrix composites, then we describe the interface region and its characteristics, properties of different metal matrix composites, and finally, we summarize different applications of metal matrix composites.

Metal Matrix Composites

Fabrication of B4C particulate reinforced magnesium matrix composite by powder metallurgy

Microstructure and mechanical properties of 6061 Al alloy based composites with SiC nanoparticles

The effect of porosity on the mechanical and fracture behaviour in Al–Si matrix alloy and composites reinforced with SiC particles of 10 and 20 vol.% in the as-cast state and after extrusion process has been studied. Matrix alloy and composites were fabricated by compocasting and extrusion. Samples were characterized by optical microscopy, image analyzer, scanning electron microscopy and tensile tests. The results demonstrate that hot extrusion considerably reduces the porosity, while size and distribution of the reinforcement particles are also affected. In the point of fracture behaviour, the existence of large porosity is more effective.

The mechanical response of Al–Si–Mg/SiCp composite: influence of porosity

Neural network based prediction of mechanical properties of particulate reinforced metal matrix composites using various training algorithms

The microstructures and mechanical properties of artificially oxidized and as-received silicon carbide particle (SiCp) reinforced pure aluminum and 2024Al composites were investigated. It was shown that surface oxidation of SiCp increased the tensile strength and fracture strain of the pure Al based composite. Diffusion of aluminum into SiO 2 during fabrication of the composite, which increased the diffusion bonding between the SiC particle and the aluminum matrix, is thought to be responsible for the increases in strength and ductility. However, the strength and ductility of the oxidized SiCp reinforced 2024Al composite were much lower than those of the as-received SiCp reinforced 2024Al composite. Based on the experimental results from DSC, TEM, EDX and SEM fractography analyses, it is suggested that the interfacial reactions related to SiO 2 depleted the magnesium in the matrix and subsequently decreased the amount of the age strengthening phase containing magnesium. The lower level of strengthening in the matrix and the formation of a thick interfacial reaction layer, which was continuous and brittle, finally led to the lower strength and ductility of the artificially oxidized SiCp reinforced composite.

Effects of reinforcement oxidation on the mechanical properties of SiC particulate reinforced aluminum composites

Structure and amorphization of the oxide on the silicon carbide surface in an SiCp/Al composite

The age hardening precipitation reactions in a ZK60 matrix composite reinforced with 12 vol.% B 4 C particles and 12 vol.% SiC whiskers were investigated using differential scanning calorimetry (DSC), Vickers hardness testing and transmission electron microscopy (TEM). It was found that the addition of the reinforcement did not change the hardening sequence observed in the monolithic alloy, but the formation of the β′ phase is considerably accelerated. The peak temperature of the β′ phase precipitation in the composite was decreased by 15°C and the time to peak hardness aged at 170°C decreased from approximately 40 h in the monolithic alloy to about 8 h in the composite. The amount, the growth rate and the stability of the precipitates near the reinforcement/matrix interface were increased. Significant dislocation hardening was produced in the composite which was retained during the whole aging process. The aging hardening efficiency of the composite, about 200 MPa, is the same as that of the monolithic alloy. A mechanism of the effect of reinforcement addition on aging response was proposed in terms of the distinct aging behaviors near the reinforcement/matrix interface and within the matrix grains.

Effects of reinforcements on the aging response of a ZK60-based hybrid composite

The oxidation behavior of B4C particles was investigated by measuring the weight changes during isothermal heating at 650 to 800°C. The interfacial microstructure and fractography of the B4Cp and SiCw reinforced ZK60 magnesium hybrid composite was studied using a scanning electron microscope (SEM), a transmission electron microscope (TEM) and an electron energy loss spectrometer (EELS). It was found that the oxidation of B4C particles in air at the temperatures investigated produced an amorphous B2O3 surface layer. The oxidation kinetics was limited by the diffusion rate of oxygen through the liquid B2O3 layer. The oxidation layer was found to dominate the interfacial reaction, the microstructure and the mechanical properties of the hybrid composite. The rod-like MgB2 and the granular MgO were produced due to the reaction between the B2O3 and the magnesium matrix. The intimate bonding between the MgB2 and both the reinforcements and the matrix is believed to be the main reason for the improvement of the mechanical properties of the composite.

The interfacial reaction and microstructure in a ZK60-based hybrid composite

Hexagonal BaLa0.3Fe11.7O19 ultrafine powders with a magnetoplumbite type (M-type) structure were synthesized by a sol-gel auto-combustion method. Precursor solutions with different composition were investigated to clarify the forming conditions of the ferrites. The crystal structure, grain size, form and magnetic properties were studied by means of X-ray diffraction (XRD), transmission electronic microscopy (TEM) and vibrating sample magnetometry (VSM). On the basis of analysing the effect of ammonia, citric acid and glycol on phase structure and magnetic properties, it was demonstrated that adjusting the pH value of the precursor solution with ammonia and adding an appropriate amount of citric acid and glycol are key steps in synthesis of ultrafine powders with single BaFe12O19 phase and excellent magnetic properties. In the presence of chelate agent (citric acid) and dispersant (glycol), under the conditions of pH about 7.0, nitrate/citric acid molar ratio of 1:3 and calcination temperature of 850°C (1 h), M-type BaLa0.3Fe11.7O19 ultrafine powders with a particle size of about 36 nm, a specific magnetization б s of 65.54 A · m2/kg and a coercive force Hc of 433 kA/m, were obtained.

Yanping Jin

Papers

Effects of reinforcement oxidation on the mechanical properties of SiC particulate reinforced aluminum composites

Structure and amorphization of the oxide on the silicon carbide surface in an SiCp/Al composite

Effects of reinforcements on the aging response of a ZK60-based hybrid composite

The interfacial reaction and microstructure in a ZK60-based hybrid composite

Effect of precursor solutions with different composition on synthesis of ultrafine BaLa0.3Fe11.7O19 using sol-gel auto-combustion technique