1,721,005 research outputs found
Developing Magnesium Alloys with a Combination of Strength and Ductility Based on Friction Stir-Based Technologies
No full textSome of the key data for the thesis "Developing Magnesium Alloys with a Combination of Strength and Ductility Based on Friction Stir-Based Technologies", including SEM/EDS/EBSD, and TEM data. They are stored in the .oipx format which can be opened by Aztec, .cpr which can be opened by AztecCrystal, and .csv and . tiff as spreadsheets and images.
Part of the data is associated with the following publications:
[1] X. Zhao, X. Zeng, L. Yuan, J. Gandra, Q. Hayat, M. Bai, W.M. Rainforth, D. Guan, A novel approach for producing Mg-3Al-1Zn-0.2 Mn alloy wire with a promising combination of strength and ductility using CoreFlowTM, Scripta Materialia 227 (2023) 115301.
[2] X. Zhao, Y. Xie, J. Gandra, M. Murphy, W.M. Rainforth, D. Guan, A Succinct Method to Recycle WE43 Mg Alloys—From Wasted Chips to Consolidated Billets, TMS Annual Meeting & Exhibition, Springer, (2024), 151-153.
[3] X. Zhao, D. Olden, B. Williams, A. Pariyar, D. Zhang, M. Murphy, P. Reed, P. Allison, B. Jordon, J. Qi, W. M. Rainforth, D. Guan, Grain growth stagnation at 525° C by nanoparticles in a solid-state additively manufactured Mg-4Y-3RE alloy, Journal of Magnesium and Alloys (2024), 4976-4987.
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Effect of cryomilling time on microstructure evolution and hardness of cryomilled AZ31 powders
Full text linkThe synthesis of nanostructured AZ31 powder by cryomilling was studied in this paper. The microstructural evolution during cryomilling, including the changes of particle morphology and internal grain size, was characterized via optical microscopy, SEM, TEM and XRD. Observations during the cryomilling produced four main findings. Firstly, cryomilling can refine the grains of AZ31 particles down to 100 nm after around 1 h milling and the minimum average grain size of about 30 nm was reached when the cryomilling time was extended to 6 h or longer. Secondly, cold welding played a dominant role in the early stage of cryomilling, while fracture took place in the late stage and surpassed cold welding. The former led to a particle size increase while the latter decreased the particle size. The minimum average particle size after 6 h cryomilling was approximately 26 μm. Thirdly, a few particles were agglomerated with other particles and could not be processed by cryomilling due to cold welding. Finally, after cryomilling 6 h and longer times, the hardness reached 162 HV which was much higher than other values reported in AZ31 alloy studies
ω phase strengthened 1.2GPa metastable β titanium alloy with high ductility
Full text linkThis paper provides a novel approach for exploiting ω phase strengthening in a metastable β titanium alloy while retaining high ductility. The addition of 1 wt% Fe into our previously designed Ti-7Mo-3Cr alloy can efficiently control the growth of ω phase following air-cooling, resulting in a ultrahigh yield strength (Rp0.2of 1210 MPa) with large ductility (εf of 0.15). Microstructural analysis of deformed alloys showed that the growth of ω phase in the air-cooled Ti-7Mo-3Cr-1Fe alloy modified the deformation mechanism from {332} twinning and dislocation slip, in the water-quenched alloy, to localized dislocation plasticity in ω-void channels
Effect of grain size and crystallographic structure on the corrosion and tribocorrosion behaviour of a CoCrMo biomedical grade alloy in simulated body fluid
Full text linkCoCrMo alloys are used in hip and knee replacements due to their excellent long-term survival rates. However, high failure rates have recently been observed associated with adverse tissue reactions. CoCrMo alloy surfaces undergo microstructural changes during wear, including the formation of ε-martensite and, occasionally, a nanocrystalline surface layer. It is not clear whether these changes are beneficial or detrimental to the performance of the component. Thus, high-pressure torsion (HPT) was employed to produce different grain sizes and crystallographic structures in a CoCrMo alloy and the corrosion and tribocorrosion behaviour were critically investigated as a function of grain size. The results reveal a degradation of the corrosion resistance for the HTP processed samples. The contributions of mechanical and corrosion material loss in tribocorrosion is also examined
Enhancing ductility and strength of nanostructured Mg alloy by in-situ powder casting during spark plasma sintering
Full text linkDue to internal processing defects, bulk nanostructured Mg alloys have high strength but extremely poor ductility. A novel and facile process was designed and in-situ powder casting was initiated during spark plasma sintering. This process significantly reduced processing induced defects, enhanced inter-particle bonding and introduced significant precipitation without extra ageing treatment, leading to improvement of the compressive strength and ductility. The compressive strain of bulk sample consisting of pure cryomilled powder was 3.6% with an ultimate strength of 500 MPa, while cryomilled powder mixed with eutectic Mg-Zn alloy powder obtained a compressive strain of 6.6% and ultimate strength of 506 MPa. The ductility of the sample with mixed powder was increased by 83% without any sacrifice of strength compared to the sample consisting of only pure cryomilled powder
A novel approach for producing Mg-3Al-1Zn-0.2Mn alloy wire with a promising combination of strength and ductility using CoreFlow™
Full text linkMg-3Al-1Zn-0.2Mn (wt.%, AZ31B) wires were successfully produced from commercial hot-rolled plates in one step using the CoreFlowTM process, a novel stationary shoulder friction stir extrusion manufacturing. CoreFlowed AZ31B wires exhibited fine grains with a heterogeneous grain size distribution of 6.5 ± 4.2 μm along the transverse direction (TD) compared with the as-received material. A weakened texture was also obtained in CoreFlowed AZ31B, with basal poles aligned parallel to TD shift toward extrusion direction (ED) from wire center to edge. Periodic needle-like regions with a distinctively different orientation from neighbouring regions were observed at the sample edge. The engineering ultimate tensile strength (UTS) and elongation (El) of the CoreFlowed sample was 258 ± 5 MPa and 22.3 ± 0.8%. The El was significantly increased by 58% with equivalent UTS compared to the as-received material. Such a good combination of strength and ductility is attributed to grain refinement with heterogeneity, texture weakening, and homogeneously redistributed second phase particles
Basal slip mediated tension twin variant selection in magnesium WE43 alloy
No full textTension twinning nucleation and evolution in Mg WE43 alloy over a large sampling area was investigated using a quasi-in-situ EBSD/SEM method during interrupted compression testing. The results showed tension twins with both high and low macroscopic Schmid factor (MSF) were activated under a compressive stress of 100 MPa with a strain rate of 10−1 s−1. Basal slip in most grains dominated at this stress, so nucleation of twin variants required little interaction with non-basal slip, which was different from other studies that reported prismatic slip and/or tension twinning were required to activate some low MSF tension twin variants. The geometric compatibility factor (m') was demonstrated to be an important factor to determine tension twin variant selection assisted by basal slip. The analysis indicated m' played a critical role over MSF in tension twin variant selection during twin nucleation stage, and final twin variant types were insensitive to increasing stress, but they inherited twin variant types determined at twin nucleation stage. Moreover, which specific grain boundary of a grain with hard orientation for basal slip would nucleate which twin variant could be also validated by m' and largely depended on two factors: (a) high value of m' with 1st or 2nd rank between the tension twinning of nucleated twin variant and basal slip in adjoining grains; and (b) intensive basal slip activity in the neighbouring grains before twin nucleation
Exploring the mechanism of “Rare Earth” texture evolution in a lean Mg–Zn–Ca alloy
Full text linkThe entire recrystallisation sequence and associated crystallographic texture evolution of Mg-0.8Zn-0.2Ca (wt.%) alloy was tracked using a quasi-in-situ electron backscatter diffraction (EBSD) method. Characteristic “Rare Earth” (RE) texture was formed, originating mainly from double twins and twinning-related shear bands consisting of compression and double twins. The RE textures appeared during the nucleation stage and were preserved during the relative uniform grain growth period because of solute segregation and concurrent precipitation although the alloying element content was very low. Ca and Zn co-segregated along grain boundaries with no evidence that segregation was preferred along special types of grain boundaries. The interactions between deformation microstructures, concurrent precipitation, solute drag, grain growth and texture evolution are discussed in detail. All the results indicate that Ca performs a similar role to that of RE elements in forming RE texture
Triple and double twin interfaces in magnesium—the role of disconnections and facets
Full text linkTwin boundaries have been shown to deviate from the twinning planes in hcp metals, and facets have often been observed in twin interfaces. This study presents a twinning disconnection-based model for faceting in single, double and triple twin boundaries in magnesium. Primary twinning disconnections predicted via symmetry arguments are shown to produce commensurate facets in single twin boundaries, which are then transformed into commensurate facets in double twin boundaries via the action of secondary twinning disconnections. In contrast, it is shown that for triple twin boundaries with tension-compression-tension twinning sequence, no commensurate facets can be produced by the action of tertiary twinning disconnections. The effect of facets on the macroscopic orientation of twin interfaces is discussed. Theoretical findings are validated by a transmission electron microscopy study of a hot rolled Mg-1.18wt%Al-1.77wt%Nd alloy. Single and double twins are observed, as well as rare triple twins, and the interface between the matrix and a triple twin is captured for the first time. Facets consistent with theoretical predictions are imaged via high-resolution TEM and macroscopic deviations of the boundaries from the primary twinning planes are measured
Verification of the use of micro-CT scanning to assess the features of entire squat type defects
Full text linkSquats and studs are defects in railheads that share features, but have different causes. This paper examined four squat and stud samples from three different traffic environments to compare features using μ-CT X-ray scans, surface and subsurface inspection. μ-CT scanning has been used before as a non-destructive method to investigate rail defects, but not the entire defect. The scans were verified and allowed the identification of areas of interest when sectioning the samples further. The scan volumes were also used to create 3D models of the crack networks for the 3 samples that were scanned. All defects contain similar superficial features but the depth and severity of the subsurface damage varies.
This work provides a visualisation of the 3D nature of studs in a way not seen before, as a 3D model the crack network from an in-service defect. The models of two of the defects showed the influence of hollow wheels initiating defects, as the crack seemed to initiate on the field side, grow down and towards the gauge side, before resurfacing as the longitudinal crack noted in all four defect samples. One sample is believed to have initiated due to contamination of the weld and the only squat sample, which failed in track, was believed to be ingot cast steel containing many inclusions.
Three samples were studs and one was a squat. Each defect developed for different reasons, although the two metro samples were similar. One of the studs shows branching of cracks that, based on its changing angle of growth, could continue to grow into transverse defects, breaking the rail. The three defects that were scanned would all be classed as studs, but their crack morphology varies, possibly because they are all from different traffic environments. They also show slight differences to other studs in literature
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