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The influence of cold rolling on the microstructural changes of 2205 duplex stainless steel was investigated. The steel samples revealed the presence of almost equal volume fraction of δ‐ferrite and austenite phase after hot rolling. During cold rolling, the above phase constituents became flattened, fragmented as well as transformed into acicular microstructural constituents with increasing amount of cold deformation. The transmission electron microscopy revealed the presence of strain‐induced α′ martensite, Moiré fringes, elongated worm‐like closed slip band channels and poorly developed dislocation cell structures. The volume percent of the constituent phases has been quantified by X‐ray diffraction analysis, which has also been substantiated by the image analysis result. The micro‐hardness measurement establishes that the work hardening capacity of austenite is more compared to ferrite.

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The present work aims to study the evaluation of the microstructure, tensile properties, hardness, corrosion behaviour of the various grades of rebars. The microstructures of all rebar samples comprise an outer tempered martensite ring with an inner core of ferrite-pearlite in between a narrow bainitic transition zone. Maximum hardness is achieved at the periphery which gradually decreases towards the centre. Chinese grade has a similarity with the Fe 600 rebar in terms of strength and % elongation, whereas Fe 500D and Fe 500 have lower strength but higher ductility. The EDS analyses of corrosion products obtained after immersion test in 5% NaCl solution for a period of 7 days apparently indicate the occurrences of iron oxy-hydroxides and iron oxides. X-ray diffraction and FTIR studies of the corrosion products formed on all thermomechanically treated (TMT) rebar surfaces after the aforesaid immersion test primarily indicate the presence of Lepidocrocite (γ-FeOOH), Goethite (α-FeOOH), Magnetite (Fe 3 O 4 ) and Maghemite (γ-Fe 2 O 3 ). Fe 500 (12 mm) and Chinese rebars have lower corrosion resistance as compared to the other rebars in 5% NaCl solution. Nevertheless, all the TMT rebars are corrosion resistant and can be satisfactorily used for construction purposes.

Metal oxide semiconductors (MOS) are well known as reducing gas sensors. However, their selectivity and operating temperature have major limitations. Most of them show cross sensitivity and the operating temperatures are also relatively higher than the value reported here. To resolve these problems, here, we report the use of palladium−silver (70−30%) activated ZnO thin films as a highly selective methane sensor at low operating temperature (∼100 °C). Porous ZnO thin films were deposited on fluorinedoped tin oxide (FTO)-coated glass substrates by galvanic technique. X-ray diffraction showed polycrystalline nature of the films, whereas the morphological analyses (field emission scanning electron microscopy) showed flake like growth of the grains mainly on xy plane with high surface roughness (107 nm). Pd−Ag (70−30%) alloy was deposited on such ZnO films by ebeam evaporation technique with three different patterns, namely, random dots, ultrathin (∼1 nm) layer and thin (∼5 nm) layer as the activation layer. ZnO films with Pd−Ag dotted pattern were found show high selectivity towards methane (with respect to H 2 S and CO) and sensitivity (∼80%) at a comparatively low operating temperature of about 100°C. This type of sensor was found to have higher methane selectivity in comparison to other commercially available reducing gas sensor.

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Nowadays DSS products are obtained by different processes e.g., casting, forging, rolling etc. The microstructure and mechanical properties of the manufactured product strongly depend on the specific process. Present study aims to study the structural and associated mechanical property changes after the deformation and heat treatment. Thermomechanical processing, which combines both deformation and heat treatment is very effective for microstructure control and various treatments have been developed to improve the mechanical properties without sacrifice of corrosion resistance. However, thermomechanical treatment is still lacking in the field of stainless steel as compared to low and high alloyed carbon steels and hence it is attempted for the improvement of mechanical properties of materials. Attempts have also been made to study the effect of cold rolling prior to heat treatment on the investigated stainless steel. EXPERIMENTAL PROCEDUREThe duplex stainless steel was obtained as cast form with approximately 50 mm square cross section. Then the material was homogenised at 1200 o C for 120 minutes in a resistancereheating furnace. The homogenised ingots were forged into bars of 12.5 mm u 12.5 mm section with a reduction ratio of 1:16 using a pneumatic hammer of 1.0-ton capacity. The forged bars were soaked at 1200 o C and hot rolled in a laboratory scale two -high rolling mill (10 HP) with 750 o C finish rolling temperatures (FRT) down to a thickness of approximately 6 mm in three passes (Fig. 1). The FRT for the steel was fixed at 750 o C with an aim to incorporate approximately 10% deformation as was feasible under the experimental facility. After completion of rolling, samples were cooled in air. The chemical composition of the investigated steel is shown in Table 1. The material was heat treated in different schedules as described in Table 2.To study the microstructures, the samples were subjected to the standard grinding and polishing techniques before etching. The steel sample was etched using aqua regia solution (75% HCl and 25% HNO 3 mixture) 6 . Properly etched samples were examined under the ZEISS (Axiovert 40 MAT) optical microscope at different magnifications and representative photomicrographs were presented. Quantitative metallographic studies were also done using image -analysis technique in order to describe the microstructures. Microstructures have been quantified by the OLYSIA -m3 soft imaging system developed by Olympus. ABSTRACTPresent study concerns the effect of deformation and heat treatment on the microstructure and mechanical properties of a duplex stainless steel. While hot rolling causes the coarse distribution of the constituent phases (ferrite and austenite), 50% cold rolling results into the elongated and splintered two -phase structure. Supersaturated ferrite structure established by water quenching from 1300°C results into the strengthening due to the formation of fine dispersed austenite precipitates within ferrite grain after isothermal heat treatment (1000°C, 0.5 hour). Duplex s...