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Expanding suitable severe plastic deformation processes seems essential to design lightweight wire-formed materials for emerging demands. In this regard, 6063 aluminum alloy in the form of wire was processed successfully by polyurethane rubber assisted-equal channel angular pressing up to 16 passes by route BC. It was found that significant improvement of hardness and strength is achieved at the initial passes due to the increment of material’s dislocations density which leads to the crystallite size decrease and lattice microstrain increase. Also, subsequent passes improve the mechanical properties with a gentle rate due to the saturation of dislocation strengthening. The fractography analysis indicated that the ductile fracture mode of the annealed aluminum decreases by imposing the ECAP process. It is related to the formation of cleavage and rive patterns and the reduction in the number and size of the dimples compared to the initial condition. Eventually, X-ray diffraction findings showed that by adding pass numbers, the isotropy degree of the aluminum sample enhances because of the lowest diffraction scattering.

The microstructure of Sn-Ag-Cu (SAC) solder joints plays an important role in the reliability of electronics, and interlaced twinning has been linked with improved performance. Here, we study the three-dimensional (3-D) shape of interlaced regions in Sn-3.0Ag-0.5Cu (SAC305) solder balls by combining serial sectioning with electron backscatter diffraction. In solder balls without large Ag3Sn plates, we show that the interlaced volume can be reasonably approximated as a hollow double cone with the common 〈100〉 twinning axis as the cone axis, and the 〈110〉 from all three twinned orientations making up the cone sides. This 3-D morphology can explain a range of partially interlaced morphologies in past work on 2-D cross-sections.

Magnesium (Mg) is a load‐bearing biocompatible material which has the ability to reduce stress shielding effect and facilitate osteocompatibility and biodegradation in the presence of body fluids. However, Mg is highly susceptible to corrosion in the physiological environment, hence leading to poor mechanical integrity. In this study, the multi‐axial hot forging (MAHF) process is performed on Mg‐3Zn alloys to study its grain refinement and possible improvement in mechanical, corrosion, and bioactivity behavior. The average grain size of the sample becomes significantly refined after the third cycle of MAHF. The yield and ultimate compressive strength of Mg‐3Zn alloys are found to increase by 70% and 41%, respectively, after the third cycle of MAHF, which is potentially due to the grain size refinement. Accelerated corrosion studies show improvements in the corrosion resistance with the refined grain structure. Additionally, in‐vitro immersion studies in the simulated body fluid for 14 days showed a reduction in the degradation rate after third cycle of MAHF, due to the increased grain boundary area, which offered more nucleation sites for apatite precipitation. This study underscores and lays the foundation for a new branch of severely deformed fine‐grained Mg‐3Zn alloy for temporary orthopedic implants.

Dendritic microstructural evolution during the solidification of Mg-Zn alloys was investigated as a function of Zn concentration using in situ synchrotron X-ray tomography. We reveal that increasing Zn content from 25 wt% to 50 wt% causes a Dendrite Orientation Transition (DOT) from a six-fold snow-flake structure to a hyper-branched morphology and then back to a six-fold structure. This transition was attributed to changes in the anisotropy of the solid-liquid interfacial energy caused by the increase in Zn concentration. Further, doublon, triplon and quadruplon tip splitting mechanisms were shown to be active in the Mg-38 wt%Zn alloy, creating a hyper-branched structure. Using the synchrotron tomography datasets, we quantify, for the first time, the evolution of grain structures during the solidification of these alloys, including dendrite tip velocity in the mushy zone, solid fraction, and specific surface area. The results are also compared to existing models. The results demonstrate the complexity in dendritic pattern formation in hcp systems, providing critical input data for the microstructural models used for integrated computational materials engineering of Mg alloys.

Sustainable recycling approaches are emerging topics for environmental safety of manufacturing technologies. Chips generated in high–speed machining (HSM) of as-quenched steels have a potential re-use for more sustainable and cost-efficient manufacturing routes, such as powder production from chip milling for additive manufacturing (AM). The objective of this study was to characterise tool-steel chips generated by HSM of an AISI-SAE H13 as-quenched workpiece and evaluate their potential use for powder production, as an alternative process to atomisation. Microhardness tests reveal that this type of waste has a suitable hardness for milling, which could be attributed to its microstructure. Chips were also analysed by X-ray diffraction, scanning and transmission electron microscopies, and transmission electron backscattering diffraction (t-EBSD) mapping. The microstructure of the areas adjacent to the adiabatic shear band (ASB), where intense material flow takes place, consists of thin martensite laths with high dislocation density and low angle grain boundaries (LAGB) or sub-grain regions. ASB consists of ultrafine and nanocrystalline grains. The results provide new insight on the grain-refining mechanism assisted by progressive martensite lath subdivision into small and near-equiaxed grains, as a direct result of intense strain accumulation and recrystallisation, endorsing HSM tool-steel chips as superior (nanocrystalline) and low-cost raw material for powder production. info:eu-repo/semantics/publishedVersion

Friction stir welding (FSW) since its invention has been attracting relevant interest for joining aluminium alloys. Due to the nature of this process, the materials can be joint without melting. Thanks to this peculiar characteristic, the issues associated with the cooling from liquid phase are avoided or considerably reduced, such as cracking, porosity, and defects. However, as well as other well-established welding techniques, the FSW process gives rise to formation of residual stress in the welding region and surrounding volume: heat and thermo-mechanical affected zones. Presence of residual stress in a mechanical component is well-known to affect its performance, particularly regarding fatigue at high number of cycles. Another aspect that influences the fatigue life is the underlying microstructure. In this work, we firstly study the residual stress field and the underlying microstructural features arising in FSW butt joints and their effect on the fatigue performance of this type of weldments. The evaluation of residual stress field is carried out by means of modern experimental techniques. In the first instance, synchrotron X-ray powder diffraction was employed for two-dimensional full field maps of residual stress. Corroboration of these measurements was done by exploiting the capability of focused ion beam and digital image correlation (FIB-DIC), which is able to deliver pointwise absolute measurement of residual stress. A set of FSW samples were then tested under uniaxial fatigue loading at several loading ranges, in the high cycle fatigue regime, in order to understand whether the severity of loads affects the crack path and life endurance. Fractographic and electron backscattered diffraction (EBSD) analysis then revealed crack nucleation site and propagation mechanisms with the respect of the underlying microstructure. Outcome of these experimental studies is then thoroughly discussed.

In the present study, aluminum alloy AA2219-T87 bars were cryorolled to various amounts of deformation in two pre-deformation conditions: (1) without solution treatment i.e., as-received T87 (WST-CR) and (2) with solution treatment (ST + CR). The solution treated and cryorolled bars were further annealed leading to a third condition: (3) solution treated, cryorolled, and annealed (CR + Annealed). Room-temperature mechanical properties have been evaluated for all three cryorolled conditions. Significant improvement in the 0.2 pct YS and UTS values was obtained for bars cryorolled to cross-sectional area reduction of more than 50 pct in the solution-treated condition (ST + CR), whereas for bars cryorolled in the without solution-treated condition (WST-CR), only an improvement in the 0.2 pct YS was observed. Cryorolling did not enhance the precipitation kinetics nor did it increase the response of the alloy to aging. The mechanical properties were correlated to the microstructures obtained by optical and transmission electron microscopy. Microstructural evolution in the ST + CR condition indicated gradual progression of the principal restoration mechanism from dynamic recovery (DRV) to dynamic recrystallization with an increasing amount of plastic deformation. Transmission electron microscopy of WST-CR and ST + CR specimens showed an increase in dislocation density as a function of the amount of deformation indicating suppression of DRV at cryogenic temperatures. Cryorolling in the solution-treated condition to cross-sectional area reduction of more than 50 pct (ST + 70 pct CR) was found to impart an optimum combination of strength and percent elongation in the present study., by Aditya Sarkar, K. Saravanan, Niraj Nayan, S. V. S. Narayana Murty, P. Ramesh Narayanan, P. V. Venkitakrishnan and Jyoti Mukhopadhyay

There is a lack of information with regards to the friction effect in ECAPed aluminum alloys, even though it might substantially modify the deformation at the surface. In this work, the friction effect at the surface and the deformation heterogeneity in the ECAPed aluminum alloy 6061-T6 were characterized. X-Ray diffraction was used to determine residual stresses (RS) on the sample surface. The volumetric sections were characterized by Synchrotron diffraction at ESRF beamline ID15B (Grenoble, France). It was found that the microhardness mapping and residual stress results showed a good agreement with the finite element analysis for the first layer studied. Minor strain variation, Delta d/d as a function of (hkl) planes, for the different analyzed sections was found. The study also showed that there was an incomplete symmetry in the residual stress near the surface, even at up to a depth of 400 gm. The regions with higher deformation were found to be at the top and bottom parts of the sample, while the central region showed stress variations of up to 50 MPa. (C) 2016 Elsevier B.V. All rights reserved.

Two types of A356 alloy castings in initial and modified with nanoparticles condition produced by gravitational casting were studied. Samples, as-cut from the castings, were subjected to light optical microscopy (LM), thermal analyses, Electron Backscattered Diffraction (EBSD) and Scanning Transmission Electron Microscopy (STEM) analyses. Results, obtained by EBSD, confirmed that there is grain refinement in samples from castings with added nanoparticles compared to the initial ones. STEM analysis shows agglomerates of nanoparticles in examined foils. Nanoparticles&rsquo, position in the microstructure confirms the hypothesis that they act as nucleating sites during the alloy solidification, which is the reason for observed fine-grained microstructure.

Wavy roll design was employed for strengthening 1 mm thin austenitic stainless steel coil sheet by cold rolling without further reduction in thickness. This steel possesses high corrosion resistance and high ductility. Initially, the sheets were rolled into sine wave shape (wave amplitude

Repeated stress-relaxation experiments are conducted from RT to 1073 K on three different gamma + alpha(2) TiAl alloys (Ti-46Al with 8Ta, 8Nb or 7Nb) One is a conventional duplex alloy, the two other are novel "convoluted" cast titanium aluminides developed for turbine applications The data include measurements of the flow stress and activation volume of these alloys at 293, 673, 873, 923, 1023 and 1073 K. Despite differences in composition, processing and microstructure, the values and evolution with temperature or with stress of these parameters are relatively similar for the three alloys This observation, coupled with the agreement of present results with data in the literature for similar alloys, leads to conclude that the strain-rate dependence of plastic flow in alloys of this class is governed by features of the gamma-phase that are relatively insensitive to the alpha 2 phase morphology. The convoluted alloys furthermore feature a yield stress anomaly. (C) 2010 Elsevier Ltd All rights reserved.

Modern concepts of the structure of liquid metals and alloys are analyzed, Several types of microinhomogeneity and microheterogeneity, of liquid metallic solutions are shown to exist. Their structure depends an their composition and pre-history Si. Using temperature and pressure variations and/or other physical effects, one can modify the structure. These changes retain down to liquidus and affect the structure and properties of the solidified alloy if the melt is cooled at appropriate cooling rate. This investigation focus on the effects of melt overheating above the liquids, Optimal thermal melting modes are specified using the results on liquid alloys structure and properties. Such optimized thermal treatment of melts (OTTM) is shown to be most efficient for rapidly quenched (RQ) metallic materials, The OTTM effects upon the structure and properties of amorphous ribbons, bulk amorphous alloys and,glass coated microwires are analyzed. (C) 2001 Elsevier Science B.V, All lights reserved.

The paper is devoted to grain-refinement of the medium-aluminium zinc based alloys (MAl-Zn). The system examined was sand cast Zn- 10 wt. %. Al binary alloy (Zn-10Al) doped with commercial Al-3 wt. % Ti - 0.15 wt. % C grain refiner (Al-3Ti-0.15C GR). Basing on the measured attenuation coefficient of ultrasonic wave it was stated that together with significantly increased structure fineness damping decreases only by about 10 - 20%. The following examinations should establish the influence of the mentioned grain-refinement on strength and ductility of MAl-Zn cast alloys.

Copyright @ 2013 ASM International. This paper was published in Metallurgical and Materials Transactions A, 44A(7), 3185 - 3197 and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited. Microstructural evolution and solidification behavior of Al-5 wt pct Mg-1.5 wt pct Si-0.6 wt pct Mn-0.2 wt pct Ti alloy have been investigated using high-pressure die casting. Solidification commences with the formation of primary a-Al phase in the shot sleeve and is completed in the die cavity. The average size of dendrites and fragmented dendrites of the primary a-Al phase formed in the shot sleeve is 43 lm, and the globular primary a-Al grains formed inside the die cavity is at a size of 7.5 lm. Solidification inside the die cavity also forms the lamellar Al-Mg2Si eutectic phase and the Fe-rich intermetallics. The size of the eutectic cells is about 10 lm, in which the lamellar a-Al phase is 0.41 lm thick. The Fe-rich intermetallic compound exhibits a compact morphology and is less than 2 lm with a composition of 1.62 at. pct Si, 3.94 at. pct Fe, and 2.31 at. pct Mn. A solute-enriched circular band is always observed parallel to the surface of the casting. The band zone separates the outer skin region from the central region of the casting. The solute concentration is consistent in the skin region and shows a general drop toward the center inside the band for Mg and Si. The peak of the solute enrichment in the band zone is much higher than the nominal composition of the alloy. The die casting exhibits a combination of brittle and ductile fracture. There is no significant difference on the fracture morphology in the three regions. The band zone is not significantly detrimental in terms of the fracture mechanism in the die casting. Calculations using the Mullins and Sekerka stability criterion reveal that the solidification of the primary a-Al phase inside the die cavity has been completed before the spherical a-Al globules begin to lose their stability, but the a-Al grains formed in the shot sleeve exceed the limit of spherical growth and therefore exhibit a dendritic morphology EPSRC and JLR

The microstructure and texture evolution of cold-rolled low carbon steel after ultrafast heating and quenching is investigated. Experiments were carried out at heating rates of 150 degrees C/s and 1500 degrees C/s. The recrystallization of ferrite is studied by scanning electron microscopy and electron backscattered diffraction techniques. The texture evolution of cold rolled steel during ultrafast heating was studied, making it possible to estimate the precise effect of heating rate on the orientations of newly formed grains. The experimental results showed that the recrystallization of ferrite was not completed before the full transformation of austenite. The noticeable increase in the fraction of recrystallized grains of diameter less than 1 mu m, when the heating rate is increased from 150 degrees C/s to 1500 degrees C/s suggests that the increase of the heating rate enhances the nucleation of ferrite. The crystallographic orientations in recrystallized ferrite are strongly influenced by the heating rates. The effect of heating rate in the releasing of stored energy, carbon diffusion and spheroidization of cementite might explain some differences in textures observed in recrystallized ferrite.

Fracture toughness tests are conducted at room temperature and 923 K (650 degrees C) on SENB (Single Edge Notched Bend) specimens of three different (alpha(2) + gamma ) TiAl-based alloys. One alloy is a conventional near fully lamellar Ti-45Al-2Mn-2Nb + 0.8%vol TiB2 XD alloy. The second and third have a composition of Ti -46Al-8Ta, with a novel "convoluted" cast microstructure developed for turbine applications and a coarse near fully lamellar microstructure, respectively. The novel alloy displays fracture toughness values of 13 +/- 2 MPa root m at room temperature and 19 MPa root m at 923 K (650 degrees C); these values approach data for lamellar microstructures, known to be optimal for this class of alloy. In particular, shear ligament toughening is observed with a role of retained lamellar colonies in toughening the convoluted microstructure. (C) 2011 Elsevier Ltd. All rights reserved.