‘The micro/nano reinforced particle’ aluminum metal matrix composites (Al-MMCs) are widely used in manufacturing sector due to light-weight, superior strength-to-weight ratio, better fracture tough...

Developments in the aluminum metal matrix composites reinforced by micro/nano particles – A review:

In situ composites are a class of composite materials in which the reinforcement is formed within the matrix by reaction during the processing. In situ method of composite synthesis has been widely followed by researchers because of several advantages over conventional stir casting such as fine particle size, clean interface, and good wettability of the reinforcement with the matrix and homogeneous distribution of the reinforcement compared to other processes. Besides this, in situ processing of composites by casting route is also economical and amenable for large scale production as compared to other methods such as powder metallurgy and spray forming. Commonly used reinforcements for Al and its alloys which can be produced in situ are Al2O3, AlN, TiB2, TiC, ZrB2, and Mg2Si. The aim of this paper is to review the current research and development in aluminum-based in situ composites by casting route.

Aluminum-Based Cast In Situ Composites: A Review

Effect of hot extrusion on wear properties of Al–15 wt.% Mg2Si in situ metal matrix composites

This research was carried out to investigate the influence of different concentrations of Mn (0.5, 1, 2, 3 and 5%) on the microstructure and tensile properties of Al–15 wt.%Mg 2 Si metal matrix composite. Microstructural examination was carried out using optical and scanning electron microscopy (SEM). The results depicted that 1 wt.% Mn addition changes the morphology of primary Mg 2 Si from irregular to polyhedral shape and its average particle size decreases from 40 μm to 12 μm. Cubic morphology of particles was also observed by the addition of 2% Mn. Further addition of Mn (>2%) did not significantly change the size or morphology of the primary Mg 2 Si. Microstructural studies also showed that Mn addition changes the morphology of the eutectic Mg 2 Si phase from flake-like to rod-like. Tensile properties of specimens with different Mn contents were also investigated. The results of tensile testing revealed that optimum Mn level for improving both UTS and elongation values is 2 wt.%. At higher Mn concentrations, an intermetallic phase (Al 6 Mn) introduced on eutectic cell boundaries appears to be the main reason for slight reduction in tensile properties. A study of the fracture surfaces via SEM revealed a brittle mode of failure in Mn free composite. However, the addition of 2 wt.% Mn changes the fracture mode to ductile by increasing fine dimples and reducing the number of decohered particles thereby increasing the composite ductility.

Effect of Mn addition on the microstructure and tensile properties of Al–15%Mg2Si composite

Refinement of Mg2Si reinforcement in a commercial Al–20%Mg2Si in-situ composite with bismuth, antimony and strontium

The effect of solution temperature on the microstructure and tensile properties of Al–15%Mg2Si composite

The microstructure, hardness and tensile properties of Al–15%Mg2Si in situ composite with yttrium addition

The effects of solution heat treatment and phosphorous addition on the microstructure and tensile properties of in situ Al–15%Mg2Si composite specimens have been investigated. The Al–15%Mg2Si composite ingot was made by in-situ process and different amounts of phosphorous (0.1, 0.3, 0.5, 0.7 and 1 wt% P) were added to the remelted composite. Then, the specimens were subjected to solutionizing at 500 °C for holding time of 4 h followed by quenching. Optical microscopy (OM) and scanning electron microscopy (SEM) indicated that phosphorous addition not only changes the morphology of primary Mg2Si particles from dendritic to a regular shape, but also it reduces Mg2Si particle size. Solutionizing led to the dissolution of the Mg2Si particles and changed their morphology to round shape. The results obtained from tensile testing revealed that both phosphorous addition and solution heat treatment improve ultimate tensile strength (UTS) and elongation (El.%) values. According to the results, the optimum tensile property was achieved by adding 0.5 wt% P to the Al–Mg2Si composite after solution heat treatment. Fractographic analysis revealed a cellular nature for the fracture surface of the MMC. As a result of P addition the potential sites for stress concentration and crack initiation areas were reduced due to microstructural modification, while increase in the number of fine dimples rendered the nature of fracture from brittle to ductile and also improved tensile properties.

Microstructure and tensile properties of cast Al–15%Mg2Si composite: Effects of phosphorous addition and heat treatment

The effects of different transient liquid phase (TLP) bonding times on the microstructure and mechanical properties of Hastelloy X joints made by Ni–Cr–B–Si–Fe filler alloy were investigated. The specimens were TLP bonded at 1070 °C for holding times of 5, 20, 80, 320, and 640 min. The electron probe microanalysis (EPMA) results revealed that the main eutectic phases observed at the joints following incomplete isothermal solidification were Ni-rich borides, Ni-rich silicides, Ni–Si eutectic, and some Cr-rich borides. A high density of plate-like, blocky, and acicular (Mo and Cr)-rich borides were observed in the diffusion-affected zone (DAZ) of the samples; however, increasing the holding time decreased the contents of these phases. The solid-state diffusion was found to be a more effective transportation phenomenon than base metal dissolution at longer holding times. The increased DAZ thickness and the complete isothermal solidification as a result of the improved solid-state diffusion helped increase the uniformity of the hardness profile of the TLP bond at higher holding times (320 and 640 min). The results showed reverse relationship between the athermally solidified zone (ASZ) width and the bonding strength. The highest tensile strength (∼617 MPa) was achieved for the sample bonded at a holding time of 320 min; this strength was more than 80% of the base metal strength. A fractographic analysis of the tensile failure revealed a cellular fracture surface, exhibiting the characteristics of both brittle and ductile fractures. The sites prone to stress concentration and crack initiation were reduced with the completion of isothermal solidification.

A. Malekan

Papers

The effect of solution temperature on the microstructure and tensile properties of Al–15%Mg2Si composite

The microstructure, hardness and tensile properties of Al–15%Mg2Si in situ composite with yttrium addition

Microstructure and tensile properties of cast Al–15%Mg2Si composite: Effects of phosphorous addition and heat treatment

Influence of bonding time on the transient liquid phase bonding behavior of Hastelloy X using Ni-Cr-B-Si-Fe filler alloy

Microstructural evolution and tensile properties of the in situ Al–15%Mg2Si composite with extra Si contents