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Magnesium (Mg) alloys despite being the ideal candidate for structural applications, owing to their high specific strength and low density, are not widely used due to lack of active slip systems at room temperature in their hexagonal close-packed crystal structure, eliciting poor ductility and formability. Amongst the various series of Mg alloys, the AZ and ZK series alloys have been standouts, as they inherit better room temperature strength and flow characteristics through their solute elements. Grain refinement, as well as eliminating casting defects through metal processing techniques are vital for the commercial viability of these alloys since they play a key role in controlling the mechanical behaviour. As such, this review highlights the effect of different Bulk-deformation and Severe Plastic Deformation techniques on the crystal orientation and the corresponding mechanical behaviours of the AZ31 alloy. However, every process parameter surrounding these techniques must be well thought of, as they require specially designed tools. With the advent of finite element analysis, these processes could be computationally realized for different parameters and optimized in an economically viable manner. Hence, this article also covers the developments made in finite element methods towards these techniques. © 2021

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Department of Design and Automation

School of Mechanical Engineering

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Journal of Magnesium and Alloys

Review on the effect of different processing techniques on the microstructure and mechanical behaviour of AZ31 Magnesium alloy

The usage of AZ31 magnesium alloy has been limited in tribology applications, due to low hardness and poor wear resistance. In this connection, the age-hardening process is a promising heat treatment process for enhancing mechanical strength and wear resistance. Hence, the present work aims to analyze the effect of the age-hardening process on the microstructure, mechanical and wear behavior of AZ31 Magnesium-Calcium hexaboride composites (Mg composite). Here, dry sliding wear behavior was analyzed with different loads (10, 20, and 30 N) and sliding velocity (0.4, 0.6, and 0.8 m. s-1) for a constant sliding distance of 2000m. Age hardened composites exhibited a higher hardness and compressive strength which was due to the increased volume of the secondary precipitates (Mg17Al12 and Al8Mn5). The morphology study revealed that there is an exhibition of shear bands and brittle fracture for Age hardened composites. The remarkable wear rate reduction was achieved for age hardening processed composites due to the increased load-bearing capacity induced by the presence of a high volume of secondary precipitates. Delamination wear is the dominant wear mechanism for the composites and the delaminated craters increases with increasing the load condition. Further, the elemental mapping on the collected wear debris was also used to confirm the wear mechanism. © 2021 IOP Publishing Ltd.

Surface Topography: Metrology and Properties

Analyzing the mechanical and wear behavior of age hardening processed AZ31 magnesium composites

The present study reports the wear behavior of Calcium hexaboride (CaB6) reinforced Nickel-Phosphorus (Ni-P) composite coating. Nickel-Phosphorus/Calcium hexaboride coatings were fabricated on mild steel with various dispersion of CaB6 in the Ni-P bath using Electroless deposition process. Surface characteristics like morphology, phase analysis, surface roughness, 3D surface image and surface hardness were measured and correlated. The composite coating of 2.0g/l dispersion of CaB6 showed no pores in the surface of the coating. Different intermetallic phases (Ni3P and Ni12P5) were formed for the heat treated Ni-P/CaB6 coatings and also found decreased for the high dispersion of CaB6 (3.0g/l). Maximum surface hardness of 832 HV0.05 and better wear resistance was obtained for Ni-P/CaB6 (2.0g/l) coating compared to other deposit. Wear track study evidenced the control of severe delamination wear of Ni-P deposit after the reinforcement of CaB6. Abrasive wear mechanism was the profound wear mechanism exhibited during the sliding of Ni-P/CaB6 coating against the En-31 steel. © 2020 Elsevier Ltd.

Materials Today: Proceedings

Calcium hexaboride reinforced Nickel-Phosphorus composite coating for increasing the wear properties of low carbon steel

Magnesium is a metal which is more abundant and has very low density but it has a low hardness and it has less wear resistance. To improve the properties of magnesium, SiC ceramic particles are reinforced. Composite is fabricated by powder metallurgy technique by varying the content of Mg in the range of 99.5%, 99%, 98.5 and 98% and SiC in the range of 0.5%, 1%, 1.5% and 2% by weight respectively. Mechanical alloying was done prior to the fabrication of composites by using ball milling with the milling parameters like ball to powder ratio, milling speed, milling duration and process control agent are 20:1, 250rpm, 10hrs, and methanol respectively. The mechanically alloyed powders were compressed in a die with the sample size of 8mm diameter with 35mm length at a pressure of 500MPa by using the 50-tonnes/ square inch hydraulic press. The compacted samples were sintered in the furnace at 550°C and maintained for 2hrs in the argon atmosphere and then furnace cooling was done to improve the sintering property. The fabricated magnesium composite samples are subjected to hardness and wear test evaluation. The wear test results indicate that the obtained higher hardness samples of 98%Mg-2%SiC composite pin shows better wear resistance and friction force responses when compared to other samples at all the parametric conditions of load and velocity. Then the wear mechanisms that has occurred on the worn out pin surface was examined by using scanning electron microscope. © 2019 Elsevier Ltd. All rights reserved.

Experimental investigation of dry sliding wear behaviour on ceramic reinforced magnesium composite by powder metallurgy technique

Dry sliding wear behavior of ultrafine-grained (UFG) AZ31B magnesium alloy processed by high pressure torsion (HPT) has been investigated against bearing steel ball at room temperature. The HPT process progressed with formation of twins (at number of torsional turns N = 0), subgrains (N = ¼) and high angle boundaries (recrystallized, grain size ∼115±21 nm, at N = 5). With the progression of HPT, hardness of the sample increased and wear rate decreased, involving abrasive, oxidative and adhesive mechanisms in all cases. A distinct feature was formation of lathy strips, whose length increased by as much as ∼1 mm with HPT torsional rotations N = 0 and ¼, but diminished after N = 5 to ∼200 µm. The lengthy lathy strips were due to twins and shear bands (which favours crack propagation path) inside larger grains, but diminished because of very fine grains size. © 2018 Elsevier B.V.

Materials Letters

Wear behavior of HPT processed UFG AZ31B magnesium alloy

The effect of calcium hexaboride (CaB6) reinforced magnesium metal matrix composite (Mg-MMC) for mechanical and tribological behavior have been investigated. Fabrication of the Mg-MMC was done by the squeeze casting process using the bottom pouring stir casting furnace. Mechanical properties such as tensile strength and hardness of the composites were analyzed. The dry sliding wear behavior of the pure Mg and the composites was evaluated in the pin-on-disk tribo-meter using SAE52100 bearing steel disk at room temperature. Improvement in the mechanical property was found in CaB6reinforced Mg-MMC as compared with pure Mg. A significant fact was that, addition of CaB6enhanced the wear resistance of Mg-MMC, revealing the delamination wear mechanism is dominant from other wear mechanisms. © 2017 Elsevier Ltd

Tribology International

Influence of calcium hexaboride reinforced magnesium composite for the mechanical and tribological behviour

Improving tribological performance of magnesium based composites in dry sliding condition is a crucial challenge. In this work, fabrication of magnesium composites has been done using squeeze casting techniques. Dry sliding wear behavior of magnesium composites were conducted on the Pin-on-Disc tribometer. Taguchi optimization technique was used to design the tribological experiments, while the grey relational analysis was used to predict the optimal tribological process parameters using multiple responses.From the results obtained, a 62.77% improvement in the predicted result of the tribological process parameter was observed when compared with middle ranked grey relational grade on the L27 orthogonal array. © 2017 Elsevier Ltd. All rights reserved.

Effect of Calcium Hexaboride Particles on Predicting the Dry Sliding Tribological Process Parameter of Magnesium Composite Using Grey Relational Analysis