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Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Rupture, Fractures, Propriété mécanique, Mechanical properties, Propiedad mecánica, Rupture ductile, Ductile fracture, Ruptura dúctil, and Verformungsbruch

It has generally been assumed that metals usually fail as a result of microvoid nucleation induced by particle fracture. Here, we concentrate on high-density micropores filled with hydrogen in aluminum, existence of which has been largely overlooked until quite recently. These micropores exhibit premature growth under external loading, thereby inducing ductile fracture, whereas the particle fracture mechanism operates only incidentally. Conclusive evidence of a micropore mechanism is provided by the observation of an instantaneous release of gas at failure. We can therefore conclude that the growth of micropores dominates ductile fracture. Since the material we used has a standard pore density, we can assume that an identical fracture mechanism operates in other aluminum alloys. This finding suggests that intense heat treatment, which is generally believed to enhance the mechanical properties through homogenization, may have entirely the opposite effect. This revelation will have a major impact on the engineering design of metals.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage base magnésium, Magnesium base alloys, Eutectique, Eutectic, Eutéctico, Eutektikum, Néodyme alliage, Neodymium alloy, Neodimio aleación, Neodymlegierung, Résistance mécanique, Strength, Resistencia mecánica, and Festigkeit

3D numerical images of the intergranular percolating eutectic of two binary alloys, Mg-0.62 at. pctLa and Mg-0.60 at. pctNd, created using dual beam FIB tomography, were incorporated into an FEM code to model their tensile behavior. Due to its high volume fraction (29.9 pct), the behavior of the Mg-La network was akin to that of a stretch-dominated micro-truss structure, whereas the Mg-Nd's, with a relatively low volume fraction (7.5 pct), mimicked that of a bending-dominated structure. The 3D network contributed some 37 MPa to the strength of the Mg-La alloy casting, whereas it only added about 1.4 MPa to the Mg-Nd's. The model predictions based on the binary alloys were verified using cast-to-shape specimens of the Mg-La and two ternary Mg-La-Nd alloys, subjected to a flash-annealing aiming at breaking up the continuity of the 3D network, while preserving the rest of the microstructure unchanged. The flash-annealed specimens exhibited a decrease in strength that matched closely the computed values. Implications regarding alloy design involving the eutectic network and solid solution hardening of more complex alloys are discussed.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Elasticité, Elasticity, Elasticidad, Elastizitaet, Module Young, Young modulus, Módulo Young, Module élasticité, Elastic modulus, Módulo elasticidad, Elastizitaetsmodul, Propriété mécanique, Mechanical properties, Propiedad mecánica, Précipitation, Precipitation, Precipitación, Ausscheidung, Précipité, Precipitate, Precipitado, and Ausscheidungsprodukt

The behavior of Young's modulus, E, was determined in aluminum alloys such as AA7075 and AA2024 at room temperature under various thermomechanical treatments. E was almost 2 pct (AA7075) and 3 pct (AA2024) lower for these materials after solution heat treatment and quenching than after annealing. When the aging time was increased, values of E tended to approach the annealing values. The variation observed was attributed to structural changes during the thermal treatments. However, when the alloys were cold deformed before or after aging, no appreciable changes in E were observed. This behavior is quite different to that observed in cold-worked pure aluminum (and also in pure iron), in which E decreased to a minimum (7 to 10 pct reduction in values) and then partially recovered with additional cold working. The variation in behavior with cold working observed in a pure material and other materials that contain a second phase with nanometric precipitates was correlated with the density of dislocations and the length of the dislocation segments generated during the cold working process.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Propriété mécanique, Mechanical properties, Propiedad mecánica, A chaud, Hot process, En caliente, Acier faiblement allié, Low alloy steel, Acero débilmente aliado, Niedriglegierter Stahl, Acier roulement, Ball bearing steel, Acero rodamiento de bolas, Kugellagerstahl, Ductilité, Ductility, Ductilidad, Verformungsfaehigkeit, Mécanisme, Mechanism, Mecanismo, Récupération, Recovery, and Recuperación

In low alloy steels containing Nb, the poor hot ductility is basically due to the austenite grain boundary segregation of sulfur and the additional matrix strengthening of Nb(C,N) precipitates, both of which decrease the equicohesive temperature. The recovery of hot ductility is therefore attributed to not only the clean grain boundaries that the segregated sulfur is scavenged through the MnS reaction but also the matrix softening by the coarse Nb(C,N) precipitates.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Propriété mécanique, Mechanical properties, Propiedad mecánica, Acier, Steel, Acero, Anisotropie, Anisotropy, Anisotropía, Limite élasticité, Yield strength, Límite elasticidad, Streckgrenze, Microstructure, Microestructura, Mikrogefuege, Pipeline, Oleoducto, Résistance choc, Impact strength, Resistencia choque, Résistance mécanique, Strength, Resistencia mecánica, and Festigkeit

We describe here the effect of microstructure on the yield strength anisotropy in high-strength microalloyed linepipe steels. The anisotropy in steel with ferrite-bainite microstructure was lower compared to the steel with ferrite-pearlite microstructure and is attributed to the significant difference in their transformation texture components, {112} 〈110〉 and {332} 〈113〉. The yield strength anisotropy is discussed in terms of crystal plasticity concept involving estimation of average orientation factor and its relation to yield strength.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage base nickel, Nickel base alloys, Solidification dirigée, Directional solidification, Solidificación dirigida, Gerichtete Erstarrung, Superalliage, Superalloy, Superaléación, and Superlegierung

In order to better understand the geometrical effect on freckle formation in superalloys, samples with uniform increases and decreases in their cross sections were directionally solidified in a Bridgman furnace. In comparison to our conventional knowledge, some new features of freckle appearance have been observed. Freckles could occur at sloped surfaces where the freckle pattern is no longer roughly parallel to the direction of gravity but has the same slope as the surface. At significantly angled surfaces, the freckles appear as discrete flakes, having the shape of tree roots, instead of the long and narrow chains which are usually observed. The component portions having inward sloping surfaces are very freckle prone while those with outward sloping surface are mostly freckle free, although the completely opposite freckling tendency is indicated by the simulated solidification condition. Therefore, as an independent factor the geometrical feature of the components can more effectively affect the freckle formation than the local thermal conditions.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Acier haute résistance, High strength steel, Acero alta resistencia, Hochfester Stahl, Déformation, Deformation, Deformación, Verformung, Microstructure, Microestructura, Mikrogefuege, Mode déformation, Deformation mode, Modo deformación, Résistance mécanique, Strength, Resistencia mecánica, and Festigkeit

The microstructure of transformation induced plasticity (TRIP) and dual phase (DP) multiphase steels after stamping of an industrial component at different strain levels was investigated using transmission electron microscopy. The TRIP steel microstructure showed a more complex dislocation substructure of ferrite at different strain levels than DP steel. The deformation microstructure of the stamped parts was compared to the deformation microstructure in these complex steels for different equivalent tensile strains. It was found that the microstructures are similar only at high levels of strain (>10 pct) for both steels.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage base aluminium, Aluminium base alloys, Alliage ternaire, Ternary alloy, Aleación ternaria, Etude expérimentale, Experimental study, Estudio experimental, Experimentelle Untersuchung, Microstructure, Microestructura, Mikrogefuege, Modélisation, Modeling, and Modelización

A numerical formulation of solidification model which can predict the microsegregation and microstructural features for multicomponent alloys is presented. The model incorporates the kinetic features during solidification such as solute back diffusion, dendrite tip undercooling, and secondary arm coarsening. The model is dynamically linked to thermodynamic library for accurate input of thermodynamic data. The modeling results are tested against the directional solidification experiments for Mg-Al-Zn alloys. The experiments were conducted in the cooling rate range of 0.13 to 2.33 K/s and microstructural features such as secondary arm spacing, primary dendrite arm spacing, second phase fraction, and microsegregation were compared with the modeling results. Based on the model and the experimental data, a solidification map was built in order to provide guidelines for as-cast microstructural features of Mg-Al-Zn alloys in a wide range of solidification conditions.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Interface, Interfase, and Grenzflaeche

The equilibrated grain boundary groove shapes of solid Cd in equilibrium with Sn-Cd-Sb liquid were observed from a quenched sample by using a radial heat flow apparatus. The Gibbs-Thomson coefficient, solid―liquid interfacial energy, and grain boundary energy of the solid Cd were determined from the observed grain boundary groove shapes. The thermal conductivity of the eutectic solid phase for Sn-35.80 at. pct Cd-6.71 at. pct Sb alloy and the thermal conductivity ratio of the liquid phase to the solid phase for Sn-35.80 at. pct Cd-6.71 at. pct Sb alloy at eutectic temperature were also measured with a radial heat flow apparatus and a Bridgman-type growth apparatus, respectively.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Abrasion, Abrasión, Addition zirconium, Zirconium addition, Adición zirconio, Zirconiumzusatz, Effet composition, Composition effect, Efecto composición, Konzentrationseinfluss, Modélisation, Modeling, Modelización, Oxyde d'yttrium, Yttrium oxide, Ytrio óxido, Yttriumoxid, Propriété mécanique, Mechanical properties, and Propiedad mecánica

Y-O nanoparticles which are homogeneously distributed in the matrix can improve the thermal properties of steels. Several studies of mechanically alloyed steels showed that especially Y-Ti-O particles can cause a further improvement of the mechanical properties at elevated temperatures. It is also assumed that an addition of Zr instead of Ti may have a similar or even stronger effect. This study presents a new way of producing nanostructured ferritic alloys as Zr is incorporated by attrition of yttrium-stabilized zirconia balls during milling. Additionally, the effect of Zr incorporation is demonstrated as well as the particle size distribution of the Y-Zr-O nanoparticles analyzed by transmission electron microscopy. This is compared to a specimen milled with common steel balls. Atom probe tomography and transmission electron microscopy show that the incorporated zirconia lowers the minimum particle size and causes a finer particle distribution. This particle refinement causes a higher hardness after hipping.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Microstructure, Microestructura, Mikrogefuege, Métal liquide, Liquid metal, Metal líquido, Fluessiges Metall, Solidification dirigée, Directional solidification, Solidificación dirigida, Gerichtete Erstarrung, Transfert chaleur, Heat transfer, Transferencia térmica, and Waermeuebertragung

Finite-element-based solidification modeling was used to investigate the thermal characteristics of the Bridgman and liquid metal cooling (LMC) directional solidification (DS) processes. Physically representative boundary conditions were implemented within a finite-element model to test its applicability to a broad range of processing conditions. The dominant heat-transfer step for each case was identified. Relationships between the thermal gradient and the solid-liquid interface position relative to the transition region of the furnace were developed. The solidification rate, the local velocity of the solid-liquid interface, and the cooling rate as a function of withdrawal rate were analyzed. The curvature of the solid-liquid interface varies with the processing conditions and influences the local thermal condition and, therefore, the morphological development of dendritic structure during solidification. An extensive sensitivity analysis of process conditions was conducted for both the Bridgman and LMC techniques. The relative importance of process parameters on the resulting thermal conditions during solidification was identified. A protocol for determination of preferred process conditions was defined. The maximum axial thermal gradient at the surface of the casting occurs when the solid-liquid interface is just above the baffle for both the Bridgman and LMC DS processes, independent of casting geometry or mold-heater temperature.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Corrosion, Action des agents de corrosion, Corrosion environments, Acier inoxydable 304, Stainless steel-304, Acier inoxydable austénitique, Austenitic stainless steel, Acero inoxidable austenítico, Austenitischer nichtrostender Stahl, Acier inoxydable, Stainless steel, Acero inoxidable, Nichtrostender Stahl, Dimension particule, Particle size, Dimensión partícula, Teilchengroesse, Oxydation, Oxidation, Oxidación, Résistance corrosion, Corrosion resistance, Resistencia corrosión, and Korrosionsbestaendigkeit

In this work, the oxidation resistance of 304 stainless steel (SS) in the uncoated and nanoceria-coated conditions was investigated at 1073 K and 1273 K (800 °C and 1000 °C) under dry air conditions. It was found that nanoceria coatings with average particle sizes of 10 nm were effective enough to fully protect the 304 SS from oxidation. In particular, when the average nanoceria particle size in the coating was less than 5 nm, the coatings were highly efficient in hindering the oxidation susceptibility of the 304 SS. Improvements in the oxidation resistance of up to two orders of magnitude were experimentally found in this work. Finite elements were used in solving Fick's Second Law using the Crank-Nicholson method in order to elucidate the active oxidation mechanisms in the bare and nanoceria-coated 304 SS. Oxygen penetration profiles across the scale were predicted suggesting that in the absence of a nanoceria coating, the oxygen concentration at a given scale depth is three times as high as in the nanoceria-coated samples. Moreover, kinetic simulations for scale growth through an exponential term containing a factor λ were satisfactory in predicting the experimental outcome on mass gain vs time. Ostwald-Ripening mechanisms were considered to be active during the dissolution of nanoceria particles. It was found that when average particle sizes fall below 5 nm in size, they tend to dissolve immediately, but the dissolution times become exceedingly long when the particle sizes increase above 10 nm.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage base titane, Titanium base alloys, Aluminium alliage, Aluminium alloy, Aluminio aleación, Aluminiumlegierung, Propriété surface, Surface properties, Propiedad superficie, Oberflaecheneigenschaft, Traitement surface, Surface treatment, Tratamiento superficie, Oberflaechenbehandlung, Vanadium alliage, Vanadium alloy, Vanadio aleación, and Vanadiumlegierung

In this research, the effect of various surface treatments including laser processing, grit blasting and anodizing on chemical structure, surface topography, and bioactivity of Ti-6Al-4V was investigated. Six groups of samples were prepared by a combination of two alternative laser processes, grit blasting and anodizing. Selected samples were first evaluated using microanalysis techniques and contact roughness testing and were then exposed to in vitro environment. Scanning electron microscopy was used to characterize the corresponding final surface morphologies. Weight measurement and atomic absorption tests were employed for determination of bioactivity limits of different surface conditions. Based on the data obtained in this study, low-energy laser processing generally yields a better biological response. The maximum bioactivity was attained in those samples exposed to a three step treatment including low-energy laser treatment followed by grit blasting and anodizing.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, and General

Oxygen ingress is critical to the high-temperature behavior of alpha + beta titanium alloys. The current study investigated the impact of crystallographic orientation on the ingress of oxygen in Ti-6Al-2Sn-4Zr-2Mo + Si, for colony microstructures. The oxygen ingress depth was estimated using EDS, EPMA, microhardenss, and optical microscopy. Results indicate that the depth of oxygen ingress in colony microstructures is dependent on α-laths' orientation relative to the ingress direction. A finite element model was developed to simulate the oxygen ingress in three different lath orientations. Results were used to calibrate the effective diffusivity for the colony microstructure. The relationships between the lath orientations, hardness, and ingress depth were discussed.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage moulé, Cast alloy, Aleación moldeada, Gusslegierung, Coulée continue, Continuous casting, Colada continua, Stranggiessen, Fonderie, Foundry, Fundería, Giesserei, Germination, Germinación, Keimbildung, Microstructure, Microestructura, Mikrogefuege, Ségrégation, Segregation, Segregación, and Seigerung

An aluminum alloy was cast by a laboratory scale horizontal twin roll caster with or without melt conditioning by the intensive shearing prior to solidification and then examined by high-resolution electron microscopy. The combined twin roll casting process with solidification formed channels and induced centerline segregation without the conditioning. In comparison, the melt conditioning minimized the severe segregation on the surface as well as at the centerline. Furthermore, large amounts of solute elements were uniformly distributed along grain boundaries or interdendritic regions. Analytical electron microscopy detected a fine oxide particle or a fragmented aluminum particle particularly at the center region of one nucleated aluminum grain. In addition, large oxide particles of about 1 to 5 μm nucleated aluminum grains easily due to low undercooling necessary for the heterogeneous nucleation, whereas small oxides with the size of about 100 to 200 nm requiring large undercooling were pushed along the grain boundaries instead of contributing to the nucleation. The enhanced nucleation of aluminum grains and well-distributed solute atoms in the melt by the melt conditioning resulted in the minimization of macro- and micro-segregations and the formation of a uniform microstructure.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Composé intermétallique, Intermetallic compound, Compuesto intermetálico, Intermetallische Verbindung, In situ, Moussage, Foaming, Espumación, and Schaeumen

The effect of in situ intermetallic formation on the foaming behavior of Al-3 wt pct Sn alloy has been investigated by introducing five different alloying elements—Co, Mg, Mn, Ni, and Ti. The alloying elements were designed, using thermodynamic calculations, to form various intermetallic phases which are (i) stable until final foaming temperature and (ii) dissolved during the foaming process. Thermal analysis using DSC was carried out to characterize the formation and dissolution of intermetallic phases during the foaming process. The foaming tests of the Al-3 wt pct Sn-X alloy were carried out using a mechanical expandometer and the macrostructure of the foam was scanned with an X-ray tomographer. It is found that the foaming behavior and foam stability of Al-3 wt pct Sn alloy can be actively controlled by the alloying elements.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage base nickel, Nickel base alloys, Superalliage, Superalloy, Superaléación, Superlegierung, Vieillissement, Ageing, Envejecimiento, Altern, Vitesse refroidissement, Cooling rate, Velocidad enfriamiento, and Abkuehlungsgeschwindigkeit

The evolution of lattice misfit in the polycrystalline nickel-base superalloy, RR1000, has been investigated using high resolution neutron diffraction at interrupted time intervals during an aging heat treatment. Samples were subjected to a super-solvus heat treatment followed by either a 100 or a 1 K min-1 cooling rate prior to aging. Irrespective of cooling rate, the lattice misfit remained unchanged at approximately 0.1 pct throughout the aging cycle, indicating the microstructure remained stable. Microstructural observations validated this result for samples cooled at 1 K min-1. However, for the faster, 100 K min-1, cooling rate, whilst the secondary γ' remained unchanged, the tertiary γ' showed significant coarsening. Simulated diffraction patterns were used to investigate the influence of volume fraction, particle size, and lattice parameter of individual γ' distributions on the measured lattice misfit. The results obtained indicate that conventional methods of measuring lattice misfit will be dominated by the γ' distribution with the highest volume fraction, and may therefore obscure subtle changes in the γ' distributions with lower a volume fraction.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Assemblage et découpage thermique: aspects métallurgiques, Joining, thermal cutting: metallurgical aspects, Soudage, Welding, Propriétés mécaniques. Rhéologie. Mécanique de la rupture. Tribologie, Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology, Frottement, Friction, Frotamiento, Reibung, Microstructure, Microestructura, Mikrogefuege, Propriété mécanique, Mechanical properties, Propiedad mecánica, Soudage friction, Friction welding, Soldeo por fricción, and Reibschweissen

Friction stir welding (FSW) was used to join 3003-H18 non-heat-treatable aluminum alloy plates by adding copper powder. The copper powder was first added to the gap (0.1 and 0.2 mm) between two plates and then the FSW was performed. The specimens were joined at various rotational speeds of 800, 1000, and 1200 rpm at traveling speeds of 70 and 100 mm/min. The effects of rotational speed, second pass of FSW, and direction of second pass also were studied on copper particle distribution and formation of Al-Cu intermetallic compounds in the stir zone. The second pass of FSW was carried out in two ways; in line with the first pass direction (2F) and in the reverse direction of the first pass (FB). The microstructure, mechanical properties, and formation of intermetallic compounds type were investigated. In high copper powder compaction into the gap, large clusters were formed in the stir zone, while fine clusters and sound copper particles distribution were obtained in low powder compaction. The copper particle distribution and amount of Al-Cu intermetallic compounds were increased in the stir zone with increasing the rotational speed and applying the second pass. Al2Cu and AlCu intermetallic phases were formed in the stir zone and consequently the hardness was significantly increased. The copper particles and in situ intermetallic compounds were symmetrically distributed in both advancing and retreating sides of weld zone after FB passes. Thus, the wider area was reinforced by the intermetallic compounds. Also, the tensile test specimens tend to fracture from the coarse copper aggregation at the low rotational speeds. At high rotational speeds, the fracture locations are placed in HAZ and TMAZ.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Alliage dilué, Dilute alloy, Aleación diluída, Verduennte Legierung, Coefficient diffusion, Diffusion coefficient, Coeficiente difusión, Diffusionskoeffizient, Diffusion, and Difusión

The diffusion coefficient of Sc in dilute Al-Sc alloys has been determined at 748 K, 823 K, and 898 K (475 °C, 550 °C, and 625 °C, respectively) using semi-infinite diffusion couples. Good agreement was found between the results of the present study and both the higher temperature, direct measurements and lower temperature, indirect measurements of these coefficients reported previously in the literature. The temperature-dependent diffusion coefficient equation derived from the data obtained in the present investigation was found to be D(m2/s) = (2.34 ±2.16) x 10-4 (m2/s)exp(-(167±6K)(kJ/mol) RT). Combining these results with data from the literature and fitting all data simultaneously to an Arrhenius relationship yielded the expression D(m2/s) = (2.65 ± 0.84) x 10-4 (m2 /s)exp((-168±2)(kJ/mol) RT) In each equation given above, R is 0.0083144 kJ/mol K, T is in Kelvin, and the uncertainties are ±1 standard error.

Crystallography, Cristallographie cristallogenèse, Metallurgy, welding, Métallurgie, soudage, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Metaux. Metallurgie, Metals. Metallurgy, Généralités, General, Développement, Development, Desarrollo, Entwicklung, Elément alliage, Alloying element, Elemento aleación, and Legierungselement

The α + β-type Ti-4.5Al-6.9Cr-2.3Mn alloy has been theoretically designed on the basis of assessment of the Ti-Al-Cr-Mn thermodynamic system and the relationship between the molybdenum equivalent and mechanical properties of titanium alloys. The alloy is successfully prepared by the split water-cooled copper crucible, and its microstructures and mechanical properties at room temperature are investigated using the OM, SEM, and the universal testing machine. The results show that the Ti-4.5Al-6.9Cr-2.3Mn alloy is an α + β-type alloy which is consistent with the expectation, and its fracture strength, yield strength, and elongation reach 1191.3, 928.4 MPa, and 10.7 pct, respectively. Although there is no strong segregation of alloying elements under the condition of as-cast, the segregation of Cr and Mn is obvious at the grain boundary after thermomechanical treatment.