The potentials of CuZnAlNi shape memory alloys to serve as viable reinforcement in Aluminium matrix composites (AMCs) was investigated. The AMCs were double stir cast developed, containing 4, 6, and 8 wt% CuZnAlNi particles; and their structural characteristics and mechanical properties were compared with that of the unreinforced Al alloy and AMC containing 8 wt% SiC. Scanning electron microscopy and X-ray diffraction results show that the CuZnAlNi refined the grain size, and increase in the CuZnAlNi wt% resulted in the formation of varied AlCu-based intermetallics, apart from the primary Al rich phase. The strength indicators – hardness, ultimate tensile strength, and specific strength largely improved with increase in the CuZnAlNi wt% and were comparatively higher than that of the unreinforced Al alloy and AMC reinforced with 8 wt% SiC for the 6 and 8 wt% CuZnAlNi reinforced AMC (specific strength being the only exception). The percentage elongation and fracture toughness values of the AMCs reinforced with CuZnAlNi (12–14.5% and 10.5–12.3 MPa m1/2) were equally superior to the SiC reinforced AMC (9% and 6.5 MPa m1/2, respectively). However, a partial reduction in the % elongation was observed with the increase in the CuZnAlNi wt%. Improved matrix/particle interface bonding, matrix refinements, thermoelastic-induced compressive residual stresses, inherent ductile, and tough nature of the SMA were advanced as mechanisms responsible for the improvements in properties.

The response of two different types of aluminium matrix composites (AMCs) reinforced with silicon carbide ceramic particulates or nickel metallic particulates to hot compression testing parameters was evaluated. The composites were produced via two-step stir-casting technique. Axisymmetric compression testing was performed on the samples at different deformation temperatures of 220 and 370 °Ϲ, 0.5 and 5 s −1 strain rates and total strains of 0.6 and 1.2. The initial and post-deformed microstructures were studied using optical and scanning electron microscopy. The results show that flow stress was significantly influenced by imposed deformation parameters and the type of reinforcements used in the AMCs. Nickel particulate reinforced aluminium matrix composite (AMC) showed superior resistance to deformation in comparison with silicon carbide reinforced AMC under the different testing conditions. In both AMCs, work hardening, dynamic recovery and dynamic recrystallisation influenced their response to imposed parameters. The signature of dynamic recrystallisation was very apparent in aluminium matrix composite reinforced with nickel particulates.

The present study investigates the hot deformation mechanisms and workability in novel AA6063-Ni-p and AA6063-Steel(p) composites using hyperbolic-sine constitutive equation. The AA6063-Ni-p and AA6063-Steel(p) composites were produced with AA 6063 as matrix, and 6 wt% Ni or 6 wt% steel particles as reinforcement for each of the composite, with the adoption of double stir casting method for the composite production. Axisymmetric compression testing was performed using Gleeble 3500 thermomechanical simulator at temperature and strain rate of 200-400 degrees C and 0.01-10 s(-1) respectively to a global strain of 0.5, while constitutive model was used to study the hot working characteristics of AA6063-Ni-p and AA6063-Steel(p) composites. The results showed that anomalous flow stress oscillations and partial insensitivity to strain rate, characterised the flow stress patterns displayed by both composites. The activation energies (Q(HW)) values derived at incremental strain, were within the range of 83.8 to 218.4 kJ/mol for AA 6063/Ni-p and 14.2 to 271.9 kJ/mol for AA 6063/Steel(p) composites. The highest values of the Q(HW), for AA 6063/Ni-p was 53% and for AA 6063/Steel(p) was 91% higher than that for self-diffusion of Aluminium (Q(SD) similar to 142 kJ/mol), which suggest that the deformation controlling mechanism was work hardening facilitated by dispersion strengthening. This was supported by the stress exponent values which exceeded 5 for both composites - affirming dispersion strengthening to dominate the deformation process. Also, the Q(HW) of the composites was intermediate in comparison with the range of 111 - 509 kJ/mol reported for AMCs of similar reinforcement composition in literature, indicating that both composites have intermediate workability. (C) 2019 Elsevier Ltd. All rights reserved.

Abstract Investigation on the hot deformability and workability of stir cast 6 wt.% steel particles reinforced aluminium 6063 matrix composites was undertaken in this study. Flow stress – strain curves generated from hot compression tests performed at strain rates of 0.01, 0.1, 1, and 10 s−1, and temperatures between 200–400°C, were used to study the flow behavior of the composite, while processing map developed from analyses of the deformation data, was used to establish the deformation mechanisms and processing safe zones for effective workability. Flow stress oscillations were observed to be prevalent at lower deformation temperatures and strain rates; largely due to the settling of reinforcement particles at grain boundary vicinities, rather than a homogeneous distribution. Also, the flow behaviour was largely strain rate insensitive. The dominant flow mechanism based on the flow stress patterns, processing map and microstructural validation was established to be dynamic recovery. Safe regions for processing based on Murty's and Gegel's criteria established the safe processing zones to be ~270–400°C at 0.01–1.0 s−1 and 380–400°C at 10 s−1. Deformation processing was unsafe at 200–260°C at 0.01–1.0 s−1 and between 200–380°C at 1.0–10 s−1.

The hot deformation behavior and workability of stir cast Al 6063 alloy reinforced with 6 wt. % Nickel particles was investigated using flow stress-strain plots, microstructural analysis and processing maps. The composites were hot compression tested at temperatures of 200 °C, 250 °C, 300 °C, 350 °C and 400 °C, and strain rates of 0.01, 0.1, 1, and 10 s −1 , while scanning electron microscopy was utilized for characterization of the ensuing microstructures. The results show that the flow stress generally decreased with increase in deformation temperature, while anomalous flow stress oscillations, linked to the pattern of particle distribution in the matrix, characterized the flow stress - strain rate relations at 0.01 s −1 strain rate. The Murty’s and Gegel’s criteria utilized to establish domains of instability at the global strain of 0.5 were found to vary considerably and the combination of both left a very narrow safe processing window for the Al6063/Ni p composite. Safe regions with peak power dissipation efficiencies occurred at temperature range of ∼390 °C–400 °C and 0.01 s −1 in the lower domain and 260 °C–350 °C and 10 s −1 in the upper domain. The dominant flow softening mechanisms were established to be dynamic recrystallisation and dynamic recovery at the lower domain and upper domains, respectively.

Isothermal compression testing of BLA-SIC hybrid reinforced Aluminium composites was performed on Gleeble 3500 thermomechanical simulator under different deformation temperatures (300–400 °C) and strain rates (0.01–1 s‑1). The flow behaviour and the softening mechanisms were established using the trend of the stress-strain curves, activation energy and microstructural examination. The results showed that flow stress increased with decreasing temperature; but was not entirely strain rate sensitive − a characteristic identified in some Al 6XXX based metallic systems. Also, uncharacteristic flow stress oscillations were observed at strain rates of 0.01 and 0.1 s‑1 while steady state flow stress was observed at 1 s‑1. The hot working activation energy was ∼290.5 kJ/mol which was intermediate to the range of 111–509 kJ/mol reported in literature for various Al based composites. It was proposed that at strain rates of 0.01 and 0.1 s‑1, dynamic recrystallization and/or dislocations-reinforcements interactions were the dominant deformation mechanism(s), while at 1 s‑1, dynamic recovery was predominant.

Abstract The job of pressure testing the tubing while running in a well was left up to running a standing valve to a nipple profile with a slick line unit. This involved multiple runs to set, test, and pull the standing valves, and with the advent of horizontal well's completion, the completion cost increases as more slick line trips are made. However, in high angle/horizontal wells, the slick-line associated hole problem has become a major challenge because of the inability of the gravity-assisted, slick line run to convey a standing valve to angles greater than 65°. This slick line limitation and associated challenges has resulted to major operators to find a more efficient method to pressure test the completion string. Various operators have done different things; including pressure testing the annulus of the string/casing to verify the tubing integrity to avoid slick line associated hole problems. In the quest to solve this problem and adding to body of knowledge, Addax petroleum team of engineers introduced a tubing tester valve as part of the completion string and used it to test the pressure integrity of the completion string connections while running in hole. In carrying out a tubing pressure test, the pumping sub with surface lines was rigged up directly on the tubing from the cement pumping unit, and pressure tested. The pressure testing exercise of this string took approximately 40 minutes. Also, to note that the tubing tester valve is a full-opening tester valve that allows completion string to self-fill while running in hole. The completion string could be pressure-tested as many times as required as it is run in the hole. The tester valve has reduced the rig non-productive time and risks associated with slick line deployments. The tester valve consists of a curved flapper valve and spring, a shear ring and locking dogs that allow the curved flapper to be fully closed during a pressure test; while the valve can be fully over ridden with a higher hydraulic pressure, which then opens a large-internal diameter through valve bore, permitting the internal diameter of the string to an unobstructed production rates and future well intervention access. The production string pressure test has been successfully carried out in sixty horizontal wells to date. The cost evaluation analysis performed between the slick line standing valve and the tubing tester valve tests for some of the wells shows cost savings as much as $240,000 per well on the jack up rig.