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In the present study, AZ91 Mg alloy was heat treated at 410 °C for 6, 12 and 24 h to investigate the influence of heat treatment on machinability and corrosion behavior. The effect of soaking time on the amount and distribution of Mg17Al12 (β – phase) was analyzed under the optical microscope. Microhardness measurements demonstrated the increased hardness with increased heat treatment soaking time, which can be attributed to the solid solution strengthening. The influence of super saturated α-grains on reducing the cutting force (Fz) with respect to increased cutting speed was observed as prominent. The corrosion behavior of the heat treated specimens was studied by conducting electrochemical tests. Surprisingly, corrosion rate of heat treated samples was observed as increased compared with the base material. From the results, it is evident that the machinability of AZ91 Mg alloy can be improved by producing super saturated α-grains through heat treatment but at the cost of losing corrosion resistance. Keywords: AZ91 Mg alloy, Solid solution, Turning, Corrosion, Machinability

Tribological characteristics of AZ91/B4C surface composites were studied under air and argon gas environments. Tests were conducted under a constant normal load of 10 N, with a sliding velocity of 0.06 m/s using a linear reciprocating tribometer. Wear tracks and debris were analyzed using scanning electron microscopy, three-dimensional contour topography, and energy-dispersive X-ray spectroscopy in order to understand the wear mechanisms. The wear rate of the specimen tested under the argon environment was found to be lower (∼60%) in comparison with that of the specimen tested under the open-air environment. The value of the friction coefficient was found to be minimum under the argon environment compared with the air environment. In the air environment, the major material loss from the test specimen was attributed to oxidation wear; whereas under the argon environment, strain-hardening effect was dominant, and the material was found to be removed by delamination wear. In addition, the worn surface morphology of the wear tracks and counter surfaces showed the involvement of abrasion and adhesion wear mechanisms. The results of the study pave the pathway for the design of lightweight surface composite material systems such as AZ91/B4C toward an efficient and robust tribo-pair applicability for a controlled environment. [ABSTRACT FROM AUTHOR]

Ni–P–BN(h)–Ag hybrid composite coatings were fabricated on the steel substrate by a scalable electroless deposition process. The optimum bath composition and operating conditions were selected to obtain defect-free composite coatings with ∼50 μm thickness. Further, to enhance the hardness, as-deposited coatings were subjected to heat treatment in a tubular furnace at 400°C for 1 h. The dry sliding wear behaviour of the as-deposited (AD) and heat-treated (HT400) composite coatings was evaluated using a linear reciprocating tribometer. The average friction coefficient of the hybrid coating was ∼0.14 (in as-deposited condition) and ∼0.16 (in heat-treated condition); these values represent 51.72% and 52.94% reduction over non-hybrid Ni-P coatings. The specific wear rate of the as-deposited and heattreated composite coatings was found to be 50% and 43% lower, respectively, than that of conventional Ni–P coatings. Detailed wear track analysis was carried out to identify underlying wear mechanisms and tribochemical interactions. [ABSTRACT FROM AUTHOR]

In the current work, ZE41 Mg alloy was processed by friction stir processing (FSP) to achieve grain refinement. In addition to grain refinement, decreased intermetallic phase (MgZn) was also observed after FSP. Increased micro-hardness was observed for the processed ZE41 Mg alloy compared to the unprocessed base alloy. X-ray diffraction (XRD) studies demonstrated the texture characteristics in FSPed ZE41. Reciprocating wear studies conducted at three different temperatures, i.e. room temperature, 125 °C, and 250 °C showed lower mass loss for the processed alloy compared to that of the base alloy, particularly at elevated temperatures. This behavior can be understood by considering the benefit gained from the smaller grains and decreased amount of intermetallic phase in the processed alloy, which reduced the abrasion wear. Hence, the present study suggests that the grain refinement and decreased MgZn phase significantly improve the temperature-dependent tribological characteristics of ZE41 Mg alloy. [ABSTRACT FROM AUTHOR]