Tubular expansion is a cold metal forming process where diameteral change is achieved by propagating a conical mandrel through the tubular either by mechanical pull or hydraulic push. Cold metal ...forming alters post-expansion mechanical and microstructural properties of tubular material, which may lead to premature failure during operation. In order to prevent tubular from failure, its post-expansion material and mechanical properties must be investigated thoroughly. Initial grains morphology, distribution of phases, and subsequent variation in material and mechanical properties due to expansion process of low-carbon LSX-80 steel tubular are investigated in the current study. The observed microstructure is typical of high strength steels with a mixture of carbon-poor and carbon-rich regions. A noticeable volume fraction of martensite phase was also observed. Presence of smaller grains in the material is a clear indication of the application of grain refinement mechanism to improve strength and toughness. Microhardness and Charpy impact tests were done on unexpanded and expanded sections of tubular in order to determine their mechanical properties. In addition, fractographic analysis was accomplished and obtained results showed that the morphology of the fractured surface was nearly alike at the macroscopic scale throughout the range of expansion ratios considered in this study. However, at the fine microscopic scale, the fractured surface was mostly ductile at low expansion ratio, while it was mainly brittle at large expansion ratio. Hence, an expansion ratio in the vicinity of 15% is highly recommended for the current tubular material in order to have adequate safe margin for down-hole application. An alternative material has to be selected and/or developed in order to realize the goal of achieving higher expansion ratio (≥30%) while preserving the tubular structural integrity after expansion.
•Novel sustainable production approach developed for Aluminum Matrix Composites•Scrap Aluminum Alloy Wheels used as matrix to develop the Novel MMC’s•X-ray diffraction analysis does not reveal any ...new phases formed in the composites•Taguchi- GRA approach adopted for optimizing the stir-squeeze casting process•High values of ultimate compressive (433 MPa) and tensile strengths (133 MPa) achieved
This work focuses on the processing, properties, microstructure, and optimization of squeeze and stir casted samples of scrap aluminum alloy wheel aluminum matrix composites reinforced with alumina. The Taguchi-Grey relational analysis method was used to optimize the stir and casting process parameters, namely, squeeze pressure, squeeze time, die preheating temperature, and stirrer speed. These stir-casted composites were analyzed based on their microstructure, hardness, tensile strength, compression strength, and wear/tribological performance. Adding alumina to an aluminum matrix improved the mechanical and tribological properties. The results showed that out of nine experiments (L1–L9) obtained from Taguchi analysis, experiments L5 and L6 exhibited the best mechanical properties. Microstructural observations revealed different morphologies in the distribution of Al2O3 and porosity in the Al matrix, depending on the process parameters. Finally, the Taguchi-GRA method was used to find the optimized process parameters and was experimentally verified. The optimized sample (M2) showed the lowest porosity (5.29%) and significantly higher ultimate compression strength (433 MPa). However, it exhibited slightly lower hardness and ultimate tensile strength when compared with the L6 and L5 samples, respectively.
Aluminum alloy 6201 is a wrought, heat-treatable alloy, which is used in electricity transmission and distribution lines. The alloy is processed in a commercial continuous casting and rolling system, ...which includes a series of in-line thermomechanical processes involving hot working, quenching, cold working and artificial aging. In this study and following cold working, the alloy is subjected to a solution heat treatment at 510 °C for an hour, quenched in ice water, and artificially aged at various temperatures for various times (150–200 °C for 2–30 h) (T6-temper) in order to investigate the effect of precipitation on mechanical properties and electrical conductivity. The results show that optimum mechanical properties and electrical conductivity were obtained after artificial aging at 155 °C for 30 h (155-30). The tensile strength was almost equal to that of the as received cold drawn wire of 326 MPa, but interestingly, electrical conductivity significantly increased to 58.6% IACS from a value of 52.7% IACS of the as received cold drawn wire. Intermetallic particles α-AlFeSi (Al8Fe2Si) and β-AlFeSi (Al5FeSi and Al9Fe2Si2) were observed in all samples, which were nucleated during solidification and homogenization; they were not affected by the aging process. β″/β′/β -precipitates formed during artificial aging, which affected the final mechanical properties and the final electrical conductivity.
► Investigated the influence of starting texture on an Mg alloy during ECAE/ECAP. ► Demonstrated its influence on the resulting flow anisotropy and tension/compression asymmetry. ► Successfully ...predicted texture evolution using the VPSC crystal plasticity model. ► Successfully predicted grain size and distribution, and grain morphology evolution. ► Demonstrated the possibility of controlling the flow anisotropy via starting texture and ECAE route.
In this article, we report on the relationship between the active deformation mechanisms and the development of texture, grain size and morphology, and dynamic recrystallization (DRX) during large plastic strain deformation of an AZ31B magnesium alloy. Equal channel angular extrusion (ECAE) is used to apply a variable amount and sequence of simple shearing at 200°C. Two different starting textures were used: basal poles either aligned with or perpendicular to the extrusion direction. A multi-scale ECAE simulation model based on crystal plasticity was employed to determine the relative contributions of different slip systems during ECAE at 200°C. These simulations clarified how different active deformation modes were responsible for specific grain size and distribution, and grain morphology as a function of the starting textures and ECAE route. For instance, we found that relatively intense prismatic slip activity suppresses DRX, which, in turn, leads to an elongated grain structure. Room temperature mechanical testing was carried out on the processed samples along three orthogonal directions to characterize flow stress anisotropy and tension–compression asymmetry. It is shown that with proper selection of the starting texture and ECAE route, it is possible to control the level of mechanical anisotropy in the processed samples and obtain strongly or weakly anisotropic mechanical response in Mg alloys.
The development of microstructure and texture of twinning-induced plasticity (TWIP) steel sheet during ECAP at two temperatures (250° and 350°) up to four passes were investigated. The high chromium ...content is the differential of this TWIP steel, a chemical element that reduces the stacking-fault energy and increases corrosion resistance. By imposing ECAP, the volume fraction of twins, dislocation density, and yield strength significantly increase while ductility decreases. This study compared the effect of temperature during applied severe plastic deformation (SPD). Thin parallel slip bands’ high density was observed, and in addition to an intense micro shear, banding took place when pressing was continued by increasing the number of passes. The martensitic transformation was not detected in the deformation-twinning microstructure after more passes. The relationship between the microstructure, strain-hardening behavior, and mechanical properties was investigated after two different deformation schedules of ECAP. The best balance between high strength and good ductility (1915 MPa and 7%) was obtained after four passes at 250 °C and 350 °C. It was found that the quantity of ECAP pass affects the displacement substructure with the formation of shear bands, subgrains, and various variants of twins. These also influenced strain-hardening behavior, microhardness, texture, and ultimate strength.
In the present study, aluminium metal matrix composites (AMCs) were successfully produced through stir-squeeze casting using a novel approach. The feasibility of using car scrap aluminium alloy ...wheels (SAAWs) as the matrix material and spent alumina catalyst (SAC) from oil refineries as reinforcement material was investigated. For the purpose of comparision, composites were also produced using AlSi7Mg (LM25 grade) aluminium alloy as a matrix and alumina as reinforcement particles through the stir-squeeze casting process. In total, four different combinations of composites (AlSi7Mg + alumina; scrap aluminium alloy + alumina; AlSi7Mg + spent alumina catalyst; scrap aluminium alloy + spent alumina catalyst) were produced and characterized. Microstructural investigations using an optical microscope and a scanning electron microscope (SEM) as well as energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) revealed that in all four composites the reinforcement formed a mixture in the eutectic silicon phase of the matrix alloy. The alumina particles' size and content ratio greatly influenced this mixture's formation and morphology. The composites produced using alumina exhibited smaller pore sizes and lower porosity as compared to the composites produced with a spent alumina catalyst. Superior mechanical properties were also obtained when using alumina as reinforcement, and better mechanical properties can mainly be attributed to the morphology of the reinforcement and silicon eutectic phase mixture. The scrap aluminium alloy + alumina exhibited the lowest porosity (7.3%) and abrasive wear loss (0.11 mg for the finest abrasive), highest hardness (58.5 BHN), and second highest ultimate tensile strength (UTS) (125 MPa) and ultimate compressive strength (UCS) (312 MPa) among the four composites.
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•A novel approach used to produce metal matrix composites from waste materials.•The alumina reinforcement combines with the eutectic silicon to form a mixture.•Acicular, blunted, needle-like mixture morphology improves mechanical properties.•Enhanced ultimate tensile (125 MPa) and compressive strength (312 MPa) obtained.
The burst pressure of commonly used ductile steel pipes in oil and gas industries, i.e. X52 and X60, is measured under internal pressure loading. The pipes were machined with circular and boxed ...defects at different orientations to simulate actual metal loss defects. Defect shapes and orientations were investigated in detail to study how they affect the failure behaviour of interacting defects. The experimental burst pressure results were compared with those obtained using existing analytical methods from Design Codes. Comparison of the results showed conservatism in the existing analytical methods which may potentially lead to unnecessary plant shutdowns and pipe repairs. The outcome of the experimental tests revealed that the shapes of the defects have very small influence on the defect interaction behaviour. The burst tests interestingly showed that the defect orientation has an important effect on defect interaction. Defects oriented in the hoop and diagonal directions showed no defect interaction even when spaced by a distance of one wall thickness, while defects oriented in the longitudinal directions showed that defects interact even when the spacing is up to six wall thickness but the interaction fades away for defects spaced at longer distances.
•Experimental 31 pipe burst tests with machined metal loss defects analysed•The effects of defect shape, orientation and interaction are investigated•Results compared with existing analytical methods from Design Codes•Degree of conservatism in the existing design codes discussed•Results show that defect orientation has an important effect on defect interaction
A hybrid optimization approach using analytical hierarchy process (AHP) combined with Taguchi-Grey has been developed and tested for the first time to optimize the stir-squeeze casting process ...parameters in the production of aluminium metal matrix composites reinforced with alumina for automotive brake disc application. The AHP method was used for assigning a weight to the response variables, which was based on experts' opinion on the importance of the response variables for brake disc application. For producing brake discs, the optimum process parameters are found to be a squeeze pressure of 100 MPa, squeeze time of 45 s, die preheating temperature of 250°C and stirrer speed of 525 rpm. Also, a confirmatory analysis was carried out to validate these optimum process parameters, and the results indicated enhanced compressive strength of 433 MPa (18.5% increase) and reduced porosity of 5.29% (13.5% decrease) in the composite.
Sucker rods are typically made of steel, and are important components of equipment such as reciprocating and progressive pumps used in various downhole applications in oil and gas wells. Chemical and ...mechanical characterizations were carried out on heat treated continuous sucker rods. These sucker rods were manufactured out of three types of steels by joining a series of coils together and subjecting them to continuous heat treatment during manufacturing. Tensile properties and hardness values were in the accepted ranges required by the operator. The fracture surfaces however demonstrated a shear type brittle fracture despite relatively high elongation-to-fracture. The fracture surface revealed unusual features in which very flat surfaces with sharp edges are present. Conventional sucker rods of grades H and D that were subjected to conventional heat treatments show completely different fracture mode. Comparison of microstructure and fracture surfaces of conventional and continuous sucker rods indicates that continuous rods were perhaps under-tempered, with insufficient tempering time.
A two-phase zinc–aluminum alloy (Zn–8
wt.% Al) has been subjected to severe plastic deformation via equal channel angular extrusion (ECAE). The alloy was successfully extruded at homologous ...temperatures around 0.5
T
m through various strain paths and magnitudes. Multi-pass ECAE processing following different routes led to the elimination of the as-cast dendritic microstructure and formed a structure of elongated, ribbon-shaped phases. Monotonic tensile tests were conducted at room temperature along the longitudinal axis of the ECAE samples in addition to the directions parallel and perpendicular to the long axis of the elongated hard eutectoid phase particles in order to reveal the effect of microstuctural morphology on the anisotropic flow response. The flow strength levels increased significantly after the first ECAE pass, and then saturated at a slightly higher value after the subsequent passes in route B
C. An average increase of about 50% in ultimate tensile strength and about 100 times increase in elongation to failure were achieved after eight ECAE passes following route B
C, as compared to the as-cast values. Despite the relative chemical homogenization between the hard and soft phases, the size and distribution of the hard phase in the matrix are found to be the dominant factor controlling the flow response of the present two-phase zinc–aluminum alloy after ECAE. The hard phase size, morphology, and distribution were also found to control the anisotropy in the flow strength and elongation to failure of the ECAE processed samples. Notable flow softening with increasing number of ECAE passes, a general observation for the ECAE processed Zn–Al alloys with Al content more than 12%, was lacking in the present alloy which was attributed to the hardening effect of the fine eutectoid particles in the eutectic matrix overcoming the softening effect of deformation-induced chemical homogenization.
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