A review on the production of metal matrix composites through stir casting – Furnace design, properties, challenges, and research opportunities

The fundamentals of coating tribology are presented in a generalised holistic approach to friction and wear mechanisms of coated surfaces in dry sliding contacts. This is based on a classification of the tribological contact process into macromechanical, micromechanical, tribochemical contact mechanisms and material transfer. The tribological contact process is dominated by the macromechanical mechanisms, which have been systematically analysed by using four main parameters: the coating-to-substrate hardness relationship, the film thickness, the surface roughnesses and the debris in the contact. The description covers both soft and hard coatings with thicknesses typically in the range 0.1–50 μm, where the interaction between the coating and the substrate is essential to the tribological behaviour. The concept is supported by experimental observations. The important influence of thin tribo- and transfer layers formed during the sliding action is shown. Optimal surface design both regarding friction and wear can be achieved by new multilayer techniques giving reduced stresses, improved adhesion to substrate, more flexible coatings and harder and smoother surfaces. The differences in contact mechanisms in dry, water- and oil lubricated contacts with coated surfaces is illustrated by experimental results from diamond-like coatings sliding against a steel ball. The mechanisms of the formation of dry transfer- and tribolayers and lubricated boundary and reaction films are discussed.

Tribology of thin coatings

In the present investigation, AA6351 aluminum alloy matrix composites reinforced with various percentages of AlN particles were fabricated by stir casting technique. The percentage of AlN was varied from 0 to 20% in a step of 4%. The prepared AA6351-AlN composites were characterized using scanning electron microscope (SEM) and x-ray diffraction (XRD). The mechanical properties such as micro-hardness, compression strength, flexural strength, and tensile strength of the proposed composite have been studied. X-ray diffraction patterns confirm the presence of AlN particles in the composites. SEM analysis reveals the homogeneous distribution of AlN particles in the AA6351 matrix. The mechanical properties of the composite were found to be noticeably higher than that of the plain matrix alloy due to augmented particle content. The produced composites exhibit superior mechanical properties when compared with unreinforced matrix alloy. Fracture surface analysis of tensile specimens show the ductile–brittle nature of failure in the composites.

Synthesis, characterization and properties of stir cast AA6351-aluminium nitride (AlN) composites

Recent progress in aluminum metal matrix composites: A review on processing, mechanical and wear properties

In the current trend, the hard ceramic particles reinforced aluminum matrix composites (AMCs) is extensively being exploited as a composite which shall be utilized for various engineering applications. In the present research, the Al-Si-Mg (AA6351) composite incorporated with aluminium nitride (AlN) filler were prepared via novel and low cost melt stirring process. This study was conducted using AA6351 aluminum alloy in conjunction with AlN particles whose percentages of incorporation were 4%, 8%, 12%, 16% and 20 wt.% in the ascending. The stir casted composites and the base alloy were characterized via X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). EDAX and XRD plots prove the occurrence of AlN filler contents in the synthesized AMCs. SEM studies exhibit the even dispersion of the reinforcement particles in the Al matrix. The effects of AlN contents on the mechanical characteristics of AA6351 matrix composites were examined. The dry sliding wear characteristics of the prepared composites was tested employing pin on disc machine. The mechanical and wear behavior of the AMCs had shown a great enhancement by the incorporation of AlN particles into AA6351 matrix alloy. The test outcomes discovered that Al/20 wt.% AlN composites had revealed superior wear resistance, hardness, yield strength and tensile strength than the AA6351 base alloy

Influence of AlN particles on microstructure, mechanical and tribological behaviour in AA6351 aluminum alloy

Hard ceramic particle reinforced aluminum matrix composites (AMCs) are considered a distinct category of advanced materials which command outstanding strength, good corrosion resistance an...

Experimental investigation on mechanical properties of AA7075-AlN composites

In the current research study, AA6351 (Al-Si-Mg) is employed as matrix material and silicon nitride (Si3N4) particles as reinforcement material to manufacture the aluminum composites (AMCs). AA6351 matrix composites incorporated with several weight fractions of Si3N4 (0, 1, 2 and 3 wt.%) were synthesized via stir casting technique. The obtained composites were characterized through a scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). EDS and XRD spectrums demonstrate the presence of Si3N4 reinforcement contents in the manufactured AMCs. The SEM analysis exhibits the even dissemination of Si3N4 particles in the Al alloy. The mechanical properties of the composites are examined by conducting several kinds of tests like compression test, impact test, tensile test and hardness test to understand the relationship between the weight percentages of reinforcement on the mechanical characteristics of the manufactured AMCs. The un-lubricant tribological characteristics of the proposed AMCs were assessed utilizing pin on disk tribometer. The hardness, compression and tensile strength of the AMCs were augmented concerning the mass proportion of reinforcement content. Finally, the wear test result reveals that the addition of nano-sized Si3N4 reinforcement contents up to a mass proportion of 3% downgrades the wear rate.

Manickam Ravichandran

Papers

Synthesis, characterization and properties of stir cast AA6351-aluminium nitride (AlN) composites

Influence of AlN particles on microstructure, mechanical and tribological behaviour in AA6351 aluminum alloy

Experimental investigation on mechanical properties of AA7075-AlN composites

Microstructural and tribological characteristics of AA6351/Si3N4 composites manufactured by stir casting

Mechanical properties and applications of Magnesium alloy – Review