Adhesive wear behaviour of cast aluminium–silicon alloys: Overview

The plasticity of AZ31 and ZK60 magnesium alloys was studied by means of hot compression deformation tests on Gleeble 1500D machines at different temperatures and strain rates. The results indicate that the thermal simulation curves of AZ31 and ZK60 have different forms under the same deformation condition. The general curves of AZ31 have the character of dynamic recrystallization that the flow stress increases to a peak and then decreases to a steady state. Most deformation curves of ZK60 have the obvious character that around 0.2 in strain the stress reaches the peak and declines rapidly to the lowest, while the other curves have the character of dynamic recrystallization. From the analysis, a deformation temperature should reasonably be selected from 250 °C to 400 °C for AZ31, while it was concluded to be 200 °C or 400 °C for ZK60.

Flow stress of wrought magnesium alloys during hot compression deformation at medium and high temperatures

The need for fuel efficiency and increased performance in transportation systems continually places new demands on the materials used. The design criteria which automobile and aerospace industries are primarily concerned with are density, strength, stiffness, and corrosion resistance. Low-density materials may reduce fuel costs, increase range, and allow larger payloads. High strength and stiffness are necessary for adequate performance and safety characteristics, while corrosion resistance helps to ensure that design lifetime is achieved.

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Corrosion and Surface Treatment of Magnesium Alloys

The study of primary Si phase in spray forming hypereutectic Al–Si alloy

Effect of cooling rate on ignition point of AZ91D–0.98 wt.% Ce magnesium alloy

Applications of magnesium alloys in the aerospace industry are limited because of their poor mechanical properties, corrosion resistance and workability. Refinement of microstructure through rapid solidification processing is one of the highly potential approaches to overcome these limitations. In the present study, the technology of processing of rapidly solidified (RS) ribbons in Mg-9%Al-1%Zn-0.2%Mn alloy has been established using melt spinning technique. The effect of wheel speed on thickness and microhardness of the ribbons is presented. Microhardness is found to increase with the wheel speed. It is further observed that microhardness of the ribbons increases with the heat treatment temperature upto 200°C and thereafter it starts decreasing. Precipitation of the intermetallic phase Mg17Al12, at temperatures upto 200°C is found to prevent the grain growth and improve the properties of the ribbons. This in-turn reveals that the temperature for secondary processing of RS ribbons in Mg-9%Al-1%Zn-0.2%Mn alloy should not exceed 200°C in order to retain the benefits of rapid solidification processing.

Development of rapidly solidified (RS) magnesium-aluminium-zinc alloy

This paper deals with a novel technique of melt treatment of hyper eutectic aluminium-silicon alloys. Various potential degassers and modifying agents have been tried out through this technique and the results show that clean melt with good degree of degassing and modification is simultaneously produced without significant pollution problems. Comparative microstructural features and mechanical properties under different melt treatment agents are also discussed.

A Novel Technique for Hyper Eutectic Aluminium-Silicon Alloy Melt Treatment

Rapidly solidified and processed Al-6Fe-3MM (MM stands for Misch Metal) has been studied for microstructural characterization through optical microscopy, transmission electron microscopy and X-ray diffraction analysis. It has been shown that the RS ribbons of this alloy could be consolidated and processed through extrusion, forging and hot rolling and that the microstructures are stable up to 300°C.

Characterization of rapidly solidified structures of Al-6Fe-3MM

In recent times there is considerable spurt in R & D activities relating to Zinc-Aluminium foundry alloys for applications in bearings. In spite of the fact that zinc alloys have excellent properties like fluidity, lower melting points and excellent alloying behaviour, the zinc foundry alloy have not been finding the expected potential of application. This is due to the fact that trace amounts of impurities like lead, cadmium and tin aggravate the chances of intergranular corrosion and premature failure.
In the present work various fluxes have been tried with a view to improving the microstructural features in Zn-8Al, Zn-12Al alloys. The results indicate that the use of a special flux improves the wear and corrosion resistance. Detailed metallographic investigations were carried out and are discussed in the paper. In the preparation of the alloys only the indigenously produced electrolytic grade zinc has been used which contains some amount of lead.

The investigation showed that this flux treatment produces Zinc-Aluminium alloys having properties comparable with those produced using special high grade zinc.

Microstructure-Property Correlation in Indigenously Produced Zinc-Aluminium Foundry Alloys

Electrical Discharge Machining (EDM)-machined maraging steel components are promising in the application field of aerospace and production tools. However, the unavoidable adverse effects of recast/white layer formation, high tensile residual stress, and micro-crack on the machined surface necessitate post-treatment techniques. The current study proposed Electropolishing (EP) as a post-treatment process to eliminate EDM’s adverse effects. The performance of EP on surface residual stress and morphology of ED machined surface was evaluated for an optimum combination of parameters, including applied voltage, polishing time, agitation, and temperature. Residual stress has been analyzed using the “sin2 ψ method” of X-ray Diffraction (XRD). After EDM, the generated surface residual stress was 407.17 MPa which had been relaxed to 35.27 MPa after EP. The surface morphology of maraging steel surfaces after EDM and EP were compared using an Atomic Force Microscope (AFM) and Field Emission Scanning Electron Microscope (FESEM). It is observed that micro-cracks, globules, voids, and thermal pitting marks were entirely eradicated following EP. It can also be seen that the EP has successfully removed the formed recast layer during EDM after 6 mins of polishing time. An average of 7.94 µm layer has been removed from the surface, removing all the surface defects. The optical profilometer analyzed the surface roughness profiles, and a 78% improvement in surface roughness was observed after EP.

R K Mahanti

Papers

Development of rapidly solidified (RS) magnesium-aluminium-zinc alloy

A Novel Technique for Hyper Eutectic Aluminium-Silicon Alloy Melt Treatment

Characterization of rapidly solidified structures of Al-6Fe-3MM

Microstructure-Property Correlation in Indigenously Produced Zinc-Aluminium Foundry Alloys

Investigation of electropolishing performance on surface residual stress and morphology of electrical discharge machined maraging steel