Effect of particle size and volume fraction on the strengthening mechanisms of boron carbide reinforced aluminum metal matrix composites

Abstract

In the present work, 6061 Al–B4C metal matrix composites with different volume fractions (5, 10, 15 and 20 vol.%) have been fabricated by a low cost modified stir casting technique. The effect of varying particulate content on the microstructure of Al–B4C composites has been qualitatively characterized using a scanning electron microscope and an optical microscope. Tensile tests were performed to study the influence of varying reinforcement content on the strengthening behavior of fabricated composites. The composite’s yield strength increases significantly as the B4C content was increased from 0 to 20 vol.%. The enhancement in strength was elucidated on the basis of strengthening mechanisms characterized by load transfer, thermal dislocation, grain size, and strain gradient strengthening. The strengthening mechanisms were quantitatively analyzed and evaluated as a function of particle size and volume fraction. A critical particle size was found to be about 45 µm, below which the strengthening contributions from different mechanism increases remarkably. At a higher volume fraction of B4C, the effect of thermal dislocation strengthening becomes more dominant as compared to other mechanisms. Furthermore, the analytical models proposed by Ramakrishnan and Chen for predicting the yield strength of particulate reinforced metal matrix composites have been extended to take into account the contribution of strain gradient effect in the strengthening mechanism of composites.

Microstructure and mechanical properties of Al–Si–Cu–Fe alloy-based ceramic particle-reinforced nanocomposites and microcomposites and a modified model to predict the yield strength of nanocomposites

“…70 According to equation (6), f ′ d-EM was the second-highest improvement factor contributing to the increase in yield strength of both N-AMCs and M-AMCs (Figure 13). This result is consistent with the study of Sekine and Chen 44 investigating the yield strength of SiC particle-reinforced Al-based composites produced by the stir casting method; on the other hand, the opposite result was obtained in the study of Raj and Thakur 46 investigating the strengthening mechanisms in Al-based composites reinforced with B 4 C particles. It can be attributed to the differences in the values of some variables, such as the type of reinforcement particles and process temperatures.…”

“…Various analytical equations and models have been developed and modified to predict the effects of the size, volume fraction, and type of the reinforcement particles on the strengthening mechanisms in the PRMMCs. 38–45 However, these models neglect the influence of at least one or more strengthening mechanisms and predict overestimated results compared to experimental results 46 since it is assumed that the reinforcement particles are uniformly distributed in the matrix and that the bond between the reinforcement particles and the matrix is strong. Moreover, none of these models take into account the negative influence of porosity in predicting the strength of the PRMMCs.…”

Experimental Investigation, Modeling, and Optimization of Wear Parameters of B4C and Fly-Ash Reinforced Aluminum Hybrid Composite

“…It can be observed that the used fly-ash is rich in SiO 2 and Al 2 O 3 content i.e., 61.04 and 24.96%, respectively, and which are responsible for enhancing the properties of the composite. Magnesium (Mg) powder and potassium-hexa-flurotitanate (K 2 TiF 6 ) flux have been added into the melt during the stirring process as wetting agents to improve the wettability of fly-ash and boron carbide with aluminum [58,64,65]. Table 5 shows the list of optimal stir casting parameters that are being used for the fabrication of hybrid composites to achieve a homogeneous distribution of reinforcements and to avoid the accumulation of reinforcements into the matrix phase.…”

“…The steps involved in the stir casting process are preheating, melting, stirring, pouring, and solidification. Initially, the aluminum 7075 was preheated at 850 • C, while simultaneously the mixture of boron carbide and flyash were also preheated at 300 • C for 2 h [58,64,65,68]. The mechanical stirrer of the impeller blade angle is 30 • , the impeller blade diameter is 50% of the crucible diameter, and this is introduced in the melt and stirred at 550 rpm.…”

Microstructure and properties of in situ Ti–Al intermetallic compound-reinforced Al matrix composites with dispersive distribution of core–shell-like structure

“…%) via a low-cost modified stir-casting technique and strengthening mechanisms were quantitatively analyzed as a function of particle size and volume fraction. 16 Al-Mosawi et al prepared an Al-based composite containing 2, 4, 7, and 10 vol. % volume fractions of α-Al 2 O 3 via hot pressing, and microstructure–mechanical property correlations were obtained as functions of α-Al 2 O 3 volume fraction.…”