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The recovery and recrystallization behaviors of low-carbon interstitial-free steel are investigated at different annealing temperatures (200-690 °C) through correlation between the changes in magnetic parameters (coercivity and r.m.s. voltage), hardness, tensile strength and high-angle grain boundary fractions (HAB). Magnetic parameters and tensile strength show a significant change within recovery region (200-500 °C), while the hardness variation is very minimal at this temperature region. On the other hand, the hardness is abruptly changed compared to magnetic properties at higher annealing temperature (550-640 °C). The grain boundary characteristics and microtexture evolution occurring at recrystallization regime are evaluated by orientation imaging microscopy (OIM) and orientation distribution function (ODF) through electron backscattered diffraction (EBSD). The increase in recrystallization fraction noticeably affects microtexture property, justifying with the strengthening of γ-fiber, weakening of α-fiber and disappearance of rotated cube component with increasing annealing temperatures.

A dragline is the largest mobile equipment on earth, and it is called the “kingpin” of any mine site. In this present investigation, a case of premature failure of a coal-handling dragline is discussed. Failure occurred in a linked component known as “thimble,” which connects the A-frame and the vertical mast of the dragline. The thimble was broken into two halves and caused the entire front structures of the dragline to collapse. Failure investigation was performed through visual examination, chemical analysis, metallography, mechanical property evaluation and fractography.

The failed pinion gear assembly of a cement plant was analyzed by visual, residual stress, microstructure and mechanical property examination to determine the root cause of its failure. It is observed that the worn out region contains several surface micro cracks, especially closer to the tip (addendum) as compared to the root (dedendum) of the gear tooth profile. The surface analysis of the worn out regions showed depletion of protective chromium oxide layer at the surface and formation of iron oxide scales due to corrosion attack by lubricants, contaminants resulted in micro pitting and subsequent wear. Residual stress measurements showed tensile residual stresses at the tip (face) of the gear teeth and large compressive stresses at the root (flank) of the gear teeth. The cross-sectional microstructure examination revealed the damages due to rolling contact surface fatigue in the form of subsurface dark etched region bands and coarsened carbides in the surface. Apart from this, the difference in the tempered core microstructure below the case hardened layer between the flank and face regions lead to compressive residual stress in case of soft core and tensile stress in case of harder core respectively. The concentration of tensile residual stresses due to untempered core at the tip aided the micro-pitting and micro-cracking due to the rolling contact surface fatigue was responsible for the initiation of surface cracks and final failure of the gear.

This paper highlights the evolution of different microstructures during short-term overheating failure of a boiler water wall tube made of SA210 Grade C steel. Short-term overheating failure of the boiler tube caused fish mouth rupture with thin lips, along the longitudinal direction of the tube with extensive tube bulging. Microstructure examination revealed elongation of grains at the fracture signifying plastic deformation due to hoop stress becoming equal to the flow stress of the tube at the elevated temperature. Overheating caused degeneration of the initial ferrite–pearlite microstructure. Spheroidization and coalescence of carbides occurred in the ferrite matrix from the initial ferrite–pearlite microstructure of the boiler tube near the ruptured region. Moreover, the formation of bainite microstructure at the fracture fish mouth opening indicates heating above the eutectoid temperature (lower critical temperature) of the tube material.

The energy-efficient quenching and nonisothermal partitioning process has been shown to engender an excellent strength-ductility combination in low alloy steels. Conventionally, these steels are quenched to a specific temperature in the martensite region, i.e. between Ms and Mf, followed by slow cooling to room temperature. However, in the present study, an attempt has been made to investigate the behaviour of low alloy steel quenched in the bainite region, i.e. temperature between Bs and Ms, followed by slow cooling to room temperature. For comparison, the same steel was also quenched to two different temperatures in the martensite region as well as direct quenched to room temperature. The XRD results showed the maximum austenite retention for a lower quench temperature in the martensite region. Both the direct quenching and the quenching and nonisothermal partitioning from the martensite region led to a microstructure dominated by the presence of auto-tempered martensitic laths. However, the sample quenched in the bainite region and subsequent slow cooling gave rise to bainite-ferrite laths containing coarse carbides. An interlath precipitation of carbides was observed for the bainite, in contrast to the intralath carbide precipitation in martensite. The austenite remained at the quench temperature decomposed to bainite during slow cooling from the bainite region, whereas M-A constituents were formed during slow cooling from the martensite region. The microstructural constituents were observed to be finest for the direct-quenched sample due to a lower quench temperature. Interestingly, the sample quenched in the bainite region showed a significant improvement in ductility, in contrast to the sample quenched in the martensite region and direct-quenched to room temperature that showed higher strength.

The effect of severe plastic straining by HPT processing on the mechanical properties and the microstructure evolution of a commercial AA 6082 alloy was studied. The HPT processing was carried out by torsion of 0.5 rotation per minute under 2 GPa load, for up to 5 turns. The material was solutionized before HPT. Mechanical homogeneity is achieved after 3 turns with a saturation hardness of ~ 165 HV and further increased to ~ 175 HV after 5 turns, while the alloy showed ~ 68 HV before HPT straining. The increase in hardness during HPT has been attributed to concurrent precipitation during HPT. The development of an ultrafine grained (UFG) microstructure was analyzed by investigating samples prepared from both the centre and the edge of the HPT discs after 1, 3 and 5 turns using TEM. In case of 1 turn, subgrain formation occurred at the edges of the disc while at the centre dislocation cell structure formation was observed. Subgrains are formed at the centre and the edge after 3 HPT turns with an average diameter of ~ 300 nm that further decreased to ~ 200 nm after 5 HPT turns. Texture evolution after 1 turn consists of formation of A*2, C, A and A- components. However, with increasing straining, these components remain stable and no new component arises. This has been attributed to continuous dynamic recrystallisation as the dominating mechanism of grain refinement that can occur in this alloy under the given severe plastic straining.

A systematic investigation of failed planetary gear in a windmill gearbox was carried out. The damaged teeth were investigated in order to determine the damage mechanisms that contributed to the failure. During the visual examination, few representative gear teeth were selected with signatures of spalling, micro pitting, cracks following the elliptical path along with fractured surfaces for further investigation. Subsequently, the SEM fractography showed beach marks indicating the fatigue as a operative mechanism for crack propagation. In addition to this, the surface residual stress analysis by x-ray method showed the tensile nature at the tip, while being compressive at the root for damaged gear teeth. Furthermore, the detailed microstructural investigation of damaged gear teeth at a cross-sectional region revealed the nucleation of microcracks at interphase boundaries, dark etch bands along with severe plastic deformation at the core that further transmitted to the elliptical crack path. Finally, it has been established that the failure was initiated due to micropitting, which aggravated the subsurface microcracks leading to spalling, macro crack growth in the elliptical path across the gear teeth leading to final fracture due to the operation of rolling contact fatigue (RCF).

In the present investigation, multiphase microstructures containing a combination of ferrite, martensite, retained austenite and carbides have been produced by altering the cooling rate in low alloy steels. The mechanical properties have been evaluated and correlated with ensuing microstructural features. The as-cast alloys were austenitized, hot rolled to about 93% reduction in thickness, followed by cooling to 200 °C on the run-out table. The cooling rates, namely 50 and 70 °C/s, were employed for this study. The steel plates were then cooled slowly to room temperature in a furnace to simulate the nonisothermal partitioning, similar to the hot-rolled coil cooling. The results show that the alloy with lower carbon and Mn content (Alloy-1) reveal ferrite formation (35.4 ± 4.1 vol%) at the cooling rate of 50 °C/s. However, at a higher cooling rate of 70 °C/s, ferrite formation was circumvented and the presence of martensite, retained austenite (6.3 ± 0.13 vol%) and carbides were observed. Although no significant difference was observed in the hardness and strength values for these two cooling rates, the presence of retained austenite at a higher cooling rate (i.e. 70 °C/s) led to better ductility and impact toughness. In the other alloy, with higher carbon and Mn addition (Alloy-2), the ferrite formation was considerably reduced even for the cooling rate of 50 °C/s. As a result, it showed higher hardness and strength (~1.5–2.0 times), with a concurrent decrease in the ductility and impact toughness, in comparison to Alloy-1.

The present paper deals with the joining of twinning induced plasticity and dual phase steels, carried out by spot welding process with two different pulse durations (200 and 380 ms), by keeping other parameters constant. The microstructural and elemental analysis of the joints was characterised by optical microscopy and electron probe microanalyser. The mechanical properties of the joint were understood from microhardness measurements across the fusion zone as well as through shear and cross-tensile tests. The pulse duration of 380 ms has resulted in good macrostructure with negligible shrinkage void. It also shows smooth transition in hardness across the twinning induced plasticity steel/nugget/dual phase steel interfaces and good mechanical properties as compared to the joint prepared by pulse duration of 200 ms. Larger pulse duration results in sufficient time for the diffusion of alloying elements and yields negligible void formation due to Kirkendall effect.

A simple method is reported for preparing graphene and nickel-decorated graphene from the petals of lotus and hibiscus flowers by heating the original petals and petals soaked in a nickel(II) chloride solution ranging 800–1600 °C under a flowing argon atmosphere for 0.5 h. The products have been characterized by scanning and transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Graphene prepared at high temperature (>1200 °C) is purer than that obtained at a lower temperature (800 °C). The presence of nickel has been found to have improved the quality of the graphene and electron density near the Fermi energy level.

The low cycle fatigue behaviour of titanium alloy IMI 834 was comparatively studied in bare condition and with titanium aluminide coating, at 600 °C in air, for compressor disc of aero engines. At higher values of total strain amplitudes (Δɛt/2), coated alloy has longer fatigue life as compared to the bare alloy which appears to be due to load shifting to the coat, but at lower values of Δɛt/2, coating seems to have no effect on fatigue life. Coating adheres well to the substrate and offers resistance to cyclic plastic deformation and hence is beneficial.

The oven belonging to a wire enameling plant was heavily oxidized resulting in the contamination of the final product. The heating chamber of the oven therefore had to be removed prematurely from service and was replaced by a new one. Investigation carried out showed high phosphorous contents in the oxide scale of service exposed AISI 321. Service exposed AISI 321 subjected to the oxidation test in laboratory did not show phosphorous in the oxide scales. The phosphorous presence obstructed the chromia layer from protecting the underlying surface. Formation of coarse chromium carbide and sigma phase in the stainless steel was observed within a short exposure time. This reduced the chromium content below the critical limit required for protective chromia formation. These were the possible reasons of early service failure of the oven.

High-pressure torsion (HPT) was used to process Al–2% Si and Al–2% Si–0.25% Sc alloys for up to five turns and the mechanical properties of the processed materials were evaluated using the ball indentation technique (BIT). The results show that the presence of Al3Sc precipitates is effective in producing higher strength levels and greater grain refinement in the Al–2% Si–0.25% Sc alloy. The introduction of scandium reduces the grain size of the Al–2% Si alloy from ∼0.38 to ∼0.15 μm after 5 turns of HPT and the corresponding maximum tensile strength is increased from ∼325 to ∼375 MPa. The grain and substructure formation in the Al–2% Si alloy is similar to aluminum with dislocation cell formation and a reasonably recovered microstructure whereas in the Al–2% Si–0.25% Sc alloy it is non-homogeneous with arrays of non-equilibrium boundaries and dislocation tangles within the grains.

Aluminum–scandium alloys were prepared having different scandium additions of 0.2, 1.0 and 2.0 wt.% and these alloys were processed by equal-channel angular pressing (ECAP) at 473 K. The results show the grain refinement of the aluminum matrix and the morphology of the Al3Sc precipitates depends strongly on the scandium concentration. The tensile properties were evaluated after ECAP by pulling to failure at initial strain rates from 1.0 × 10−3 to 1.0 × 10−1 s−1. The Al–1% Sc alloy exhibited the highest tensile strength of ∼250 MPa at a strain rate of 1.0 × 10−1 s−1. This alloy also exhibited a superior grain refinement of ∼0.4 μm after ECAP where this is attributed to a smaller initial grain size and an optimum volume fraction of dispersed Al3Sc precipitates having both micrometer and nanometer sizes.

Al-TiN (10, 20, 30 wt.%) composites were fabricated by using microwave radiation. Al and TiN powders were selected as starting materials, mixed in a ball mill for ~10 min and sintered for various times. Results indicate that an optimum microwave sintering time of 2 min was essential and responsible for the improved densification and mechanical properties. The presence of TiN particles at grain boundaries plays a significant role in improving the densification and hardness values. Dry sliding wear results show the improved wear resistance of the composite (Al-TiN) due to the presence of TiN particles and the wear results are superior to the Al-TiN samples made by hot pressing technique.

The improvement in strength of Al and Al–0.2Sc alloys through repetitive corrugation and straightening (RCS) was studied. The RCS was carried out using both single teeth as well as multiple teeth corrugative setup attached to a universal testing machine. The improvement in strength was obtained by measuring the hardness after processing. The rotation of sample by 90° between successive passes resulted in higher hardness values as compared to the simple bending and straightening. The increment in hardness obtained with same number of passes in the case of Al–0.2Sc alloy is more as compared to Al and is possibly due to blocking of dislocations that are introduced during deformation by Al3Sc precipitates.

The strain-hardening behavior of Al–1 wt.% Sc alloy was studied and compared with that of Al. Al showed a linear hardening, whereas the Al–1 wt.% Sc alloy showed two-stage behavior for the same equivalent true strain up to 2.0. Transmission electron microscopy studies revealed that dislocation pile-up and dynamic recovery control the hardening behavior in Al, whereas the effective pinning by fine Al 3 Sc precipitates and dynamic recrystallization at large strain are responsible for the two-stage behavior in Al–1 wt.% Sc alloy.

Use of granulated blast furnace slag has become increasingly popular in the manufacture of blended cement, generally referred to as Portland Slag Cement (PSC).