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In this study, Charpy impact test specimens were prepared by cutting Al 7075 alloy according to ASTM-E23 standards. The prepared test specimens were dissolved in a single-phase region for 1 hour at 480°C in vacuum atmosphere and artificially aged at 120°C for 24 hours after quenching. After the first step aging heat treatment applied, the specimens were artificially aged for 5-50 hours at 180°C for the second time. Microstructural characterization and fracture surface analyzes of the specimens were determined using SEM (Scanning Electron Microscope) device, crystallographic analysis of the precipitated phases were determined using XRD (X-ray diffraction) device. The increase in the amount of ηı phase (MgZn2) with increasing double aging heat treatment time was effective in increasing the strength. After 10 hours of double aging heat treatment, the impact toughness value is improved by 300% compared to the single aged condition. [ABSTRACT FROM AUTHOR]

Mn54-xAl43C3Zrx (x?=?1, 3) alloys were prepared by rapid solidification followed by heat treatment to produce the ferromagnetic τ phase. The substitution of Zr for Mn in the structure resulted in an increase of the saturation magnetization (Ms) compared to that of Mn54Al43C3. While the highest Ms (128?±?1?emu/g) was obtained in Mn53Al43C3Zr1, the coercivity was also improved to 1.62 kOe, compared to 1.25 kOe for Mn54Al43C3. To further improve the coercivity through grain refinement, additional C (1%, 3%, 5%, and 7%) was added to Mn53Al43C3Zr1. An increase in the coercivity was observed due to a decrease of grain size and the formation of nonmagnetic phases, which reduced the magnetostatic interactions between the τ-phase grains. However, excess C reduced the saturation magnetization due to the formation of the other non-ferromagnetic phases, including ε, γ2, and β phases. [ABSTRACT FROM AUTHOR]

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Hot metal gas forming (HMGF) is a desirable way for the automotive industry to produce complex metallic parts with poor formability, such as aluminum alloys. A simple hot gas forming method was developed to form aluminum alloy tubes using flame heating. An aluminum alloy tube was heated by a flame torch while the tube was rotated and compressed using a lathe machine and simultaneously pressurized with a constant air pressure. The effects of the internal pressure and axial feeding on expansion and wall thickness distribution were examined. The results showed that the proposed gas forming method was effective for forming aluminum alloy tubes. It was also indicated that axial feeding is a vital parameter to prevent reductions in wall thickness by supplying the material flow during the forming process. [ABSTRACT FROM AUTHOR]

The shock response of the aluminum alloy 6061, and its variation according to heat treatment have been monitored via the placement of stress gauges in such orientations so as to be sensitive to the lateral component of stress, and hence the shear strength. To complement these measurements, the postshock microstructure and mechanical response have also been determined via full one-dimensional recovery techniques. Results have shown that the solution treated (T0) state, as a largely single phase material displays a fast rising shock pulse with a significant degree of hardening behind the shock front. This indicates that a high degree of dislocation generation is expected. Postshock analysis of recovered samples has confirmed this hypothesis, with dislocation cells being observed and a notable increase in the yield strength in comparison to the as-received material. In contrast, the aged (T6) experiments showed a much longer rise time with a lower degree of hardening behind the shock front. Microstructural analysis postshock shows a more randomized dislocation distribution, with little or no postshock hardening occurring once the shock induced strain has been accounted for. This has been attributed to the presence of fine Mg2Si precipitates inhibiting the motion and generation of dislocations. These measurements are in agreement with work previously carried out on this material. Comparison of the shear strengths of the two heat treatments also shows that although the T6 condition is a little higher than T0, the differences are somewhat lower than expected. [ABSTRACT FROM AUTHOR]

p-type 4H-SiC epitaxial layers grown by chemical vapor deposition have been implanted with 200 and 100 keV protons at five different implantation temperatures. An isochronal annealing series was performed from 100 to 1800 °C, and Al-doped epitaxial layers have been characterized by means of deep level transient spectroscopy (DLTS) after each annealing step. DLTS measurements were carried out in the 150–670 K temperature range and revealed the presence of eight hole traps located in the 0.18–1.8 eV range above the valence band (EV). Heat treatments for temperatures above 700 °C showed the progressive reactivation of the Al doping in the implanted region, which is completed after a 1500 °C annealing treatment. Two traps located at EV+0.44 eV and EV+1.8 eV are persistent even after annealing at 1800 °C, while the other traps anneal out after heat treatments at ≤1700 °C. An activation energy for dissociation of 6.2 eV is estimated for the hole trap at EV+0.79 eV, and the nature of this defect is discussed on the basis of previous experimental results and theoretical calculations. Furthermore, the study of the annealing behavior as a function of the implantation temperature shows that the detected traps display an increase of concentration for increasing implantation temperatures. [ABSTRACT FROM AUTHOR]

Heat treatment for precipitation hardening is known to have a significant effect on the nano/microstructure of cast aluminum alloys, and thereby affecting its properties. In this study, precipitation kinetics after solutionizing and water quenching have been characterized by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and microhardness evaluations under different aging conditions. The Kissinger methodology was applied along with the Lee–Kim–Starink–Zahra kinetic equation to determine the kinetic parameters from the DSC runs at constant heating rates, assuming that the precipitates have an ellipsoidal shape. The TEM results showed evidence of semi-coherent θ′ precipitation in accordance with the microhardness evolution during isothermal aging at 190 °C and the kinetic analysis from the DSC data. The TEM bright field images of the specimens aged at two different times were used to record the size and number density of the precipitates. The activation energies for the precipitation kinetics of θ and θ′ were 330 and 114 kJ/mol, respectively. Finally, the values for the interfacial mobility were determined using the kinetic parameters derived from the DSC results and the TEM observations. [ABSTRACT FROM AUTHOR]

Abstract Forming at elevated temperatures can significantly increase the ductility of aluminium alloys enabling the manufacture of complex-shaped panel components from sheets. This study describes and investigates two elevated temperature forming processes: Hot Form Quench (HFQ®) (Lin et al., 2008) and conventional hot forming (HF) of aluminium alloys, with various material condition and processing parameters in order to advance the understanding of forming characteristics and post-formed strength. High temperature uniaxial tensile tests of AA7075 under HFQ® and HF conditions were performed to compare the stress-strain behaviors, ductility, and post-formed hardness. The results have shown that the ductility for HFQ® condition was greater than that for the HF condition when forming temperature was below 400 °C. In addition, typical microstructural evolution, such as the low-melting phase of HFQ® and precipitation of HF, were identified using fracture morphology observations and used to explain ductility differences exhibited in these processes. Post-formed hardness resulting from HF with different initial alloy temper and forming conditions were determined and compared with those from HFQ®. Severe reduction in hardness was found for HF using both high quench-sensitive alloy AA7075 and low quench-sensitive alloy AA6082. For the first time, the effects of a variety of influencing factors are investigated systematically, including heating rate, initial alloy, temperature and strain rate, on the high temperature deformation and post-formed strength of heat-treatable aluminium alloys, which contributes to the thorough understanding of the correlation between forming conditions and microstructural evolutions. [ABSTRACT FROM AUTHOR]

Abstract Process optimization and heat treatment of AlSi10Mg aluminum alloy parts fabricated by laser melting deposition (LMD) based on coaxial powder feeding are conducted in this paper to improve manufacturing quality. The microstructures and mechanical properties of the LMD-built AlSi10Mg alloy parts are systematically investigated. Experimental results show the relative density of the block samples increase to 99.2% without larger pores and cracks after process optimization. The sample microstructures are found to display directional rapid solidification characteristics, with the Al-Si eutectic microstructure containing three microstructures being cellular, columnar dendrites and divergent dendrites. With solution and artificial aging heat treatments, Si atoms are rejected from the supersaturated Al matrix to form small Si granular particles. The heat treated samples display a uniform microstructure without heterogeneities and the microhardness remains stable at 118 HV. When the as-built sample is heat treated for solution time 2h, tensile strength increases from 292 MPa to 342 MPa due to the formation of strengthening phase Mg 2 Si. [ABSTRACT FROM AUTHOR]

Abstract In-spite of all of the unique properties of nanocrystalline materials, they are notorious when it comes to their susceptibility to thermally induced grain coarsening, thus imposing an upper limit to their application temperature. In this study, we demonstrate a coupled Monte Carlo-molecular dynamics simulation-guided experimental approach of improving the resistance to thermally induced grain coarsening in light-weight nanocrystalline Al-Mg alloys. The structure, grain boundary segregation of Mg, and extent of grain coarsening of the Al-Mg alloys were characterized using plan view and cross-sectional scanning transmission electron microscopy and atom probe tomography. Coarsening resistance is attributed to a combination of thermodynamic stabilization of grain boundaries by controlled Mg segregation, and kinetic stabilization through pinning of the boundaries with nanoscale intermetallic precipitates. Thus, we highlight the opportunities in extending the upper limit of application temperature for nanocrystalline alloys by using a complementary thermodynamic and kinetic stabilization approach. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract The microstructure and texture after plastic deformation are strongly dependent on the corresponding manufacturing process and subsequent annealing which significantly affect the properties of the final products. In this study, 1060 aluminium alloy with a thickness of 464 μm was micro flexibly rolled to a constant thickness ratio of 3.6 by a combined control of the roll gap, the rolling speed and the roll lifting speed. Afterwards, the rolled specimens were subjected to isochronal annealing at a temperature range of 200 to 400 °C for 30 min and isothermal annealing at 400 °C for 10–60 min. Results indicate that the microstructure, microhardness and texture of each thickness zone are distinctly influenced by the rolling parameters and annealing conditions. Specimens annealed at 400 °C for 30 min result in a relatively steady hardness distribution along the transition zones. Typical β fibre texture is observed in the specimens suffered from annealing while S is predominant in both micro flexibly rolled and annealed specimens. Highlights • Inhomogeneous behaviour of aluminium alloy after micro flexible rolling and annealing • Microstructure and texture evolution along the varying thickness zones of micro flexibly rolled strips • The mechanics based on the special deformation features was proposed. • Isothermal and isochronal annealing on the recrystallised characteristics of thin varying thickness strips [ABSTRACT FROM AUTHOR]

A homogeneous equiaxed grain structure is necessary for semisolid forming of aluminum alloys. One of the methods used to obtain such microstructure is strain induced melt activated process. The aim of this work is to optimize the heat treatment parameters for extruded 7075 alloy required to obtain the spheroidal grain structure suitable for thixoforging. For this purpose, 7075 was subjected to isothermal heat treatment at two different temperatures, 620 and 630 ∘C for 5, 10, 15, 20, 25, 30, 35 and 40 min. Optical microscopy analysis and mechanical tests were carried out to characterize the effects of different isothermal heat treatment parameters. Optimal heat treatment parameters were determined by the change in mechanical properties and microstructure. It was found that at 630 ∘C for 25 min resulted in 564 MPa yield stress, 616 MPa tensile stress and 5.3% elongation as the highest values in the experimental work carried out in this study. [ABSTRACT FROM AUTHOR]

In this work, an alternative statistical multiple linear robust regression methodology was used to analyze the experimental data obtained from tensile tests performed on heat treated samples of an aluminium 6063 alloy. The proposed methodology allows the identification of empirical relations between the ageing temperature and process time with the mechanical strength (UTS) and yield point (YS) of the alloy. Through these empirical relationships: a) UTS=0.0932TatA−0.1356tA2−0.0002434Ta2tA+0.00063tA3 and b) YS=5.10Ta−20.32tA−0.05281Ta2+0.2297TatA+0.0001459Ta3−0.0006192Ta2tA, obtained by using the multiple linear robust regression methodology, it was possible to find that an ageing temperature of 192 °C for 120 min would produce the maximum strength levels for the Al-6063 alloy. For such alloy, empirical relationships were successfully determined for ageing heat treatment design. [ABSTRACT FROM AUTHOR]

Influence of zirconium and scandium modifiers in the filler wire and of arc oscillations due to electric current flowing through the filler section in nonconsumable electrode argon-arc welding, as well as of friction stir welding process on formation of weld structure in sheet aluminium alloys 1460 and 1201, was studied. Curves of metal hardness distribution in the zone of permanent joint formation were plotted, and ultimate strength of samples was determined directly after welding and after their artificial ageing. It is shown that application of friction stir welding yields higher values of ultimate strength of the metal of welds and welded joints on aluminium alloys 1460 and 1201, than in automatic nonconsumable electrode argon-arc welding with weld pool oscillations, even at application of welding wire with zirconium and scandium. Here, the maximum strength level (75 % for alloy 1201 and 86 % for alloy 1460), compared to base material, is achieved after artificial ageing of samples, at which phase insformations and processes of stabilization of the structure of metal after thermal impact, take place. [ABSTRACT FROM AUTHOR]

Abstract For a non-heat-treatable Al-5Mg alloy sheet, Zn was selected as an additive for precipitate hardening in the alloys. As the Zn content increases to 5 wt%, for recrystallized sheets, a high elongation to failure, along with the high tensile strength, was observed due to the activities of deformation band formation and grain boundary sliding. After aging treatment at 120 °C, Al-5Mg-5Zn alloy was reinforced by τ-phase (Mg 32 (Al,Zn) 49) precipitates because the phase is formed the addition of 3.54 wt% Zn in Al-5Mg alloy. The precipitates are effective in the alloy, showing a yield strength of 433.4 MPa, the value of which is 4-times higher than that of Al-5Mg alloy. Thus, for a proper selection when adding Zn element to Al-5Mg alloy, a reinforcement of the strengthening mechanism can be induced, leading to much higher strength without a degradation of the elongation to failure. [ABSTRACT FROM AUTHOR]

Appropriate S‐N fatigue design curves for friction stir welded joints in aluminium alloys are currently not specified in design codes and standards. The present paper is intended to assist in enabling standardised fatigue design for such joints, through a comprehensive statistical analysis of more than 500 individual sets of data gathered from published literature. These data are used to establish the usual design fatigue curves for welds that give a 97.7% survival probability with 95% confidence. Experimental fatigue data represent defect‐free butt joints and include both flat plate and tubular joints between similar aluminium alloys (across the range of 2xxx, 5xxx, 6xxx, and 7xxx series). Weld conditions include as‐welded, machined, and postweld heat treated under constant amplitude cyclic loading at various stress ratios in the range from R = −1 to 0.5. A systematic comparison is presented by categorising the data according to the alloy type, temper condition, postweld heat treatment, and stress ratio and the correlation with the S‐N design curves from Eurocode 9 is also considered. The fatigue curves presented in this paper will serve as a useful guideline for engineers involved in design of friction stir aluminium joints subjected to in‐service fatigue loading. [ABSTRACT FROM AUTHOR]

The corrosion resistance and mechanical properties of 7075 aluminum alloy are improved by retrogression and reaging (RRA) heat treatment. Due to the complex process of RRA heat treatment, a Taguchi L25 orthogonal array is designed to optimize the process parameters of RRA heat treatment. In this work, analysis of variance was performed to find out the significant heat treatment parameters. Microstructure, mechanical properties, intergranular corrosion, exfoliation corrosion and stress corrosion cracking behaviors of 7075 aluminum alloy after RRA heat treatment were investigated by tensile test, slow strain rate test, transmission electron microscope and scanning electron microscope. Results showed that the RRA treatment involving preaging at 120 °C for 16 h, retrogression at 200 °C for 8 min and reaging at 120 °C for 24 h resulted in a desired combination of corrosion resistance and mechanical properties. [ABSTRACT FROM AUTHOR]

In this paper, the effects of strontium addition and T6 heat treating both in isolated and combined forms on the fatigue life of A356 alloy has been studied. Rotating and bending fatigue tests were carried out by using constant amplitude. Additionally, the tensile tests and micro hardness tests, the observations of microstructural characterization and fracture surface were performed. A direct relationship between the static and cyclic properties of the alloy was observed. Experimental fatigue results indicated that the alloy at T6 condition showed the best behavior, mainly in low cycle and the strontium modified alloys were shown to have slightly lower performance in low cycle. At N ≅ 2 × 10 6 cycles of load the four materials fail with almost the same alternating stress. As fracture analysis, the changes in silicon particles morphology is confirmed to interfere in fatigue crack propagation and in fracture mode. The main findings are that, at T6 conditions A356 alloys show a better fatigue life in LCF and that in HCF no significant modification in fatigue strength was noticed. [ABSTRACT FROM AUTHOR]

Hot tearing tendency of A380 with various element additions (Sr, Sr+Ti, Ti, B and B+Sr) was investigated. Constrained rod casting (CRC) hot tearing test method was used to characterize the hot tearing sensitivity. Reduced pressure test (RPT) samples were produced from each condition and all trials were repeated three times. Number density of pores on the cross section of RPT samples was calculated via digital image processing and statistical analysis was carried out. Microstructure analysis was carried out to observe the effect of alloying elements. Hot torn cross sections were subjected to SEM analysis. It was found that in aluminum alloys, the most deleterious defects, bifilms that are the cause of many defects, play an important role in initiating the hot tearing during solidification. It is important to note that the shape, size and distribution of bifilms are too complex. They act as heterogeneous nucleation site for liquid to separate and thus increase hot tearing. [ABSTRACT FROM AUTHOR]

This study investigates the wear behavior of Al hybrid composites produced by adding 4 % Ti and different amounts of B4C (ex situ) to the AA7075 alloy produced by powder metallurgy method in order to obtain TiAl3 (in situ) reinforcement phase. Different amounts of B4C (3 %, 6 % and 9 %) were added to the 4 % Ti added AA7075 alloy. Preformed parts were sintered in controlled atmosphere (argon) heat treatment furnace at 580 °C for 4 hours and then cooled. After the sintering process, the samples were characterized with scanning electron microscopy, X-ray diffraction and density and hardness measurements. Wear tests of the samples were conducted at 1ms-1 sliding speed, under 30N load for 6 different sliding distances (500–3000 m). As a result of the study, the density of the AA7075 alloys, added 4 % Ti and different amounts of B4C, was observed to decrease by the increasing amount of reinforcement elements. Also, the highest hardness value was measured for the 9 % B4C added AA7075 alloy. Wear test results showed that the weight loss of the aluminum hybrid composites increased with the increasing sliding distance. On the other hand, it was observed that weight losses of composites decreased with increasing amount of B4C. [ABSTRACT FROM AUTHOR]

In this paper, the castability of Al-6wt%Zn-2wt%Mg-2wt%Cu alloy with different titanium levels was investigated with a constrained rod casting (CRC) mold. With the increasing level of titanium, the hot tearing sensitivity (HTS) index decreased from the value of 17 (without Ti) to the value of 7 (0.06 wt% of Ti). But further increasing of titanium weight percentage will deteriorate the castability of the alloys. The HTS index increased from the value of 7 (0.06 wt% of Ti) to the value of 13 (0.24 wt% of Ti). The grain sizes and grain morphologies of as-cast as well as solid solution-treated samples with different Ti levels were measured and analyzed. For the CRC mold castings, the grain size decreased with the increasing of Ti levels in the as-cast samples, and the grain morphology was changed from dendrite to globular. The Ti level required for minimum grain size decreased as the cooling rate of solidification increased. After solid solution treatment, abnormal grain growth occurred only in samples with less than 0.1 wt% of Ti. The tensile samples with different Ti levels were cast in the tilt pouring cast machine with permanent mold. The tensile test results of heat-treated samples show that the samples with grain growth during heat treatment did not affect the tensile properties. [ABSTRACT FROM AUTHOR]

Residual stresses induced during quenching of aluminum alloys cause dimensional instability and distortion. In this study, the effects of different concentrations of polyalkylene glycol (PAG) quenchants on residual stresses and mechanical properties of 2024 aluminum alloy were investigated. Surface residual stresses were measured by using hole-drilling strain-gauge method. Also, mechanical properties and microstructure of the heat-treated samples were analyzed using hardness measurements, tensile tests, and transmission electron microscopy. Results showed that quenching into a 15% polymeric solution and aging at 190 °C for 12 h cause 50% reduction in residual stress as compared with quenching in water at 20 °C and naturally aging. Moreover, tensile strength decreased by 104 MPa (~ 20%) in compared with the T6 sample. [ABSTRACT FROM AUTHOR]

The sliding wear behaviour of microwave processed, SiCp and Al2O3p reinforced aluminium alloy 2900 and 2024 metal matrix composites prepared by powder metallurgy method was investigated in a pin on disc system. The objective is to determine the effects of novel alloying elements of AA 2900, ceramic addition and microwave aging process on the strength to tribological properties. This composite is evaluated to be an effective replacement for conventionally available AA 2024 composites in brake applications. Compared to conventional heat treating processes, microwave processing used for heat treating the samples is observed to be novel method in improving the strength-microstructural-tribological properties. AA 2900 with 6 wt-% Al2O3 exhibited good strength to microstructure relationship with excellent wear characteristics compared to AA 2024 composites which are governed by alloying elements in AA 2900. 2 H aged AA 2900 with 6 wt-% Al2O3 sample exhibited good frictional coefficient values with good density and strength characteristics. Hence, it is observed that alloying elements in AA 2900 and microwave processing have enhanced the strength to tribological behaviour where the property enhancement is achieved only through ceramic reinforcements. [ABSTRACT FROM AUTHOR]

Al-2219 alloy belongs to the class of age-hardenable materials applied in many industrial applications. To impart strength in components, it is usually tempered to T6 condition through age-hardening process. However, during this process, the components experience distortion thus adversely affecting the form accuracy. The present work is aimed at devising an appropriate processing route to produce age-hardened components through Incremental Sheet Forming (ISF) with reasonable accuracy and formability. Three different processing routes namely P-ISF-ST-T6 (ISF followed by solution treatment which is followed by age-hardening), P-ST-ISF-T6 (solution treatment followed by ISF which is followed by age-hardening) and P-ST-T6-ISF (solution treatment followed by age-hardening which is followed by ISF) are applied to produce a pyramid shape. The tensile properties of the starting sheet blank are observed to have significant influence both on the form error and formability. Yield strength appears to control the error in the flat wall and corner of pyramid in a way that the error decreases with a decrease in strength. Low yield strength, however, contrarily promotes geometrical error in the bottom of pyramid. Corner in the pyramid geometry suffers from the maximum error. Regarding formability, it is found to be governed by the area reduction in tensile fracture. The least cumulative error with reasonably high formability is offered by the P-ST-ISF-T6 route. The processing route is found to influence the distribution of residual stresses as well. The nature/magnitude of stresses in the material is transformed when ISF is performed, which further experience transformation if exposed to heat treatment. The material processed through the P-ST-T6-ISF route endures the maximum residual stresses, the route that also induces the highest form error. This reveals that higher residual stresses could cause higher form error in ISF. [ABSTRACT FROM AUTHOR]

Semisolid slurry of A357 aluminum alloy was prepared using a temperature-controllable electromagnetic stirrer and rheo-diecast at different temperatures. The effects of pouring temperature and electromagnetic stirring (EMS) on the porosity in rheo-diecast samples, as well as the relation between porosity and mechanical properties, were investigated. The results show that pouring temperature and EMS had minor influences on rheo-diecast microstructure but marked influence on the porosity. With decreasing slurry pouring temperature, the porosity decreased first and then increased, whereas the maximum pore ratio (ratio of shape factor to diameter of the largest pore) increased first and then decreased. The maximum pore ratio determines the level of tensile strength and elongation, and higher mechanical properties can be obtained with smaller and rounder pores in samples. The mechanical properties of the rheo-diecast samples increased linearly with increasing maximum pore ratio. The maximum pore ratio was 1.43 µm−1, and the minimum porosity level was 0.37% under EMS condition for the rheo-diecast samples obtained at a pouring temperature of 608 °C. With this porosity condition, the maximum tensile strength and elongation were achieved at 274 MPa and 4.9%, respectively. It was also revealed that EMS improves mechanical properties by reduction in porosity and an increase in maximum pore ratio. [ABSTRACT FROM AUTHOR]

Pores and cracks are usually inevitable in the coatings fabricated by plasma spraying. Herein, thermal chemical reaction technique was developed as an effective low-temperature strategy for addressing this issue. Dense α-Al 2 O 3 /AlPO 4 coating was synthesized on the surface of the plasma sprayed Al 2 O 3 -based coating by thermal chemical reaction at 500 °C. The α-Al 2 O 3 /AlPO 4 composites permeated into the coating and effectively filled up the pores and cracks inside. The sealed coating showed a uniform and dense morphology. The hydrogen permeation rate of the sealed coating sharply decreased by a factor of 15, which further confirmed its significantly improved compactness. In addition, the coating exhibited good thermal shock resistance and bond strength after sealing. Considering its low-temperature heat treatment, facile fabrication process and wide applicability, thermal chemical reaction method can be potentially used as a cost-saving strategy for sealing plasma sprayed ceramic coatings. [ABSTRACT FROM AUTHOR]

The aim of this paper was to determine the effect of heat treatment for the corrosion resistance of the ZnAl40Ti2Cu alloy under "acid rain" conditions. ZnAl40TiCu alloy after supersaturation and after supersaturation and aging was studied. Potentiodynamic studies, potentiostatic studies and studies on structure of the alloy top layer of samples after corrosion tests were carried out. These investigations indicated a significant influence of heat treatment on corrosion resistance of the ZnAl40Ti2Cu alloy. The highest increase in corrosion resistance comparing to the alloy in the as-cast condition may be obtained by supersaturation. A significant influence of the aging temperature and time on corrosion resistance was proved. [ABSTRACT FROM AUTHOR]

Summary: Among the common materials, metals can be hardly destroyed by flame or the heat emanating from a normal fire. Consequently, investigation on the thermal patterns produced on metallic objects after fire exposure can provide important physical evidence for fire cause/origin determination. Aluminum alloy is widely used in our daily life and the industry; hence, it can be easily found on a domestic or industrial fire scene. In this paper, the aluminum alloy 5052 was exposed in the simulated combustion gases with and without kerosene in the range of 300 to 500°C. Mass change, morphologies, and microstructures of each sample were carefully characterized by thermogravimetric analysis, morphologic observation, and electron microscopy observation with energy‐dispersive spectroscopy analysis after exposure. As expected, the microstructure of alloy changed during high temperature exposure. At the same time, an oxide scale formed and was thickened on the surface of alloy. The results reveal that the temperature can significantly affect the growth of oxide scale and the metallurgical microstructure of alloy. It is noteworthy that the presence of kerosene in the combustion gas accelerated oxidation rate and produced oxide scales different from those formed in air. These feature evolutions in surface oxide are expected to offer complementary insight on determining the fire characteristics, such as the exposure temperature, period and whether liquid accelerant is involved. [ABSTRACT FROM AUTHOR]

Summary: Energy dissipaters constructed in precast structures play an important fuse‐type role in concentrating damage and protecting the primary structure. The stable tensile and compressive deformation capacity, easier fabrication method, and relatively lower cost are expected in energy dissipater to further enrich its practical application. In this paper, a new bamboo‐shaped fuse‐type energy dissipater consisting of an inner bamboo‐shaped core with slubs and an outer circular tube was developed with high‐precision, all‐metal machining, avoiding the adverse effect of grouting and welding. The aluminum alloy was applied to fabricate the proposed energy dissipater to improve the durability. A series of tests, containing 12 specimens, was performed to address the low‐cycle fatigue behavior of bamboo‐shaped dissipaters, and stable hysteretic curves were obtained without any local and overall buckling. The deformation of the core was evidently affected by slubs, which were restrained by the outer tube. Furthermore, parametric studies on design variables including length of segments, the length of slubs, the number of segments, and the size of gap between the slub and the tube are performed. On the basis of test results of all specimens, aluminum alloy bamboo‐shaped dissipaters show a promising future for wide application in new or retrofitted buildings, which require excellent seismic behavior and durability. [ABSTRACT FROM AUTHOR]

Web crippling is a phenomenon where section webs cripple due to a concentrated force. This phenomenon could be caused by web buckling for slender sections or by web bearing/yielding for stocky sections. The aim of this study is to investigate the web bearing design rules for relatively stocky sections. Experimental tests and numerical modelling results on aluminium alloy square and rectangular hollow sections (SHS/RHS) subjected to web bearing are presented. The tests were conducted under four loading conditions: end-two-flange (ETF), interior-two-flange (ITF), end-one-flange (EOF), and interior-one-flange (IOF). Two different bearing lengths, 50 mm and 90 mm, were investigated. The test specimens were fabricated by extrusion using 6063-T5 and 6061-T6 heat-treated aluminium alloys. Web slenderness values (i.e. the width-to-thickness ratio h / t ) ranging from 2.8 to 28.0 have been considered. Non-linear finite element (FE) models were developed and validated against the test strengths and specimen failure modes. Upon validation, the FE models were used to perform a parametric study in order to supplement the experimental work. A total of 138 web bearing data consisting of 34 test results and 104 numerical results were generated in this study. In the ETF and ITF loading conditions, all specimens failed by material yielding at the webs. For the EOF and IOF loading conditions, specimens failed by flexural failure, interaction of web bearing and bending effects or material fracture at the tension flanges. The generated data is used to assess the web bearing design equations in the existing design codes as well as to propose new design rules. The new design rules for ETF and ITF loading conditions are proposed with the consideration of strain hardening effects. Further analyses have been carried out to show the newly proposed design rules are not only accurate and consistent, but also safe and reliable. [ABSTRACT FROM AUTHOR]

An improved model is proposed for automated cold metal transfer (CMT) welding based on a time-dependent double-ellipsoidal volumetric heat flux distribution. Equations are evaluated numerically within COMSOL Multiphysics for CMT welding of a 3-mm-thick AA5754 Al–Mg alloy plate. The simulation calculates transient and steady-state temperature distributions within the weld seam and heat-affected zone (HAZ). Validation of the model is achieved by comparing simulated temperatures with measured values from thermocouples in the HAZ during welding experiments, as well as through comparison of the calculated fusion zone and microscope images of the weld seam. Under steady-state conditions, large differences between the peak and average calculated temperatures in the weld pool highlight the underlying phenomenon responsible for improvements in weld quality for thin sheets with CMT compared to conventional joining processes. The developed simulation provides opportunities for process optimisation and sensitivity analysis in many applications. [ABSTRACT FROM AUTHOR]

This communication demonstrates the efficacy of heat treatment on the improved deposition characteristics of aluminum alloy powders. A novel furnace was constructed for solutionizing of feedstock powders in an inert atmosphere while avoiding sintering. This furnace design achieved sufficiently high cooling rates to limit re-precipitation during powder cooling. Microscopy showed homogenization of the powder particle microstructures after heat treatment. Cold spray deposition efficiency with heat-treated powders substantially increased for the alloys AA2024, AA6061, and AA7075. [ABSTRACT FROM AUTHOR]

The present study is focussed on investigating the effect of heat treatment variables on the formation of precipitate free zones (PFZs) in the AZ80 Mg alloy. The effect of solutionizing temperature, quenching media, aging temperature and time on the PFZ development has been systematically examined. Scanning electron microscopy and nanoindentation were employed to characterize the PFZ regions. Electron probe micro analysis (EPMA) was used to examine the role of solute depletion in the formation of these zones. Moreover, the estimation of vacancy concentration profiles near the grain boundary was used to investigate the role of vacancy depletion. The solute depletion is found to be the dominant mechanism in the development of PFZ regions as compared to vacancy. [ABSTRACT FROM AUTHOR]

A heat-treatable Al-3.5Cu-1.5Mg-1Si alloy is successfully fabricated by selective laser melting and is investigated concerning microstructures and mechanical properties. The as-prepared samples show a fine-granular microstructure in the individual melt pool of the tracks and a coarse-granular microstructure in the areas between the tracks. After T6 heat treatment, the grain size of the specimens increases slightly and the Q phase formed in the as-prepared specimens transforms to Al 2 Cu(Mg), Mg 2 Si, and Al x Mn y . All Al-Cu-Mg-Si specimens before and after heat treatment fracture around the defects that were generated during processing and show intergranular fracture along columnar grains upon tensile quasi-static loading. The as-fabricated samples exhibit a yield strength (YS) of 223 ± 4 MPa and an ultimate tensile strength (UTS) of 366 ± 7 MPa with an elongation of 5.3 ± 0.3%. After T6 heat treatment, the YS and UTS increase dramatically to 368 ± 6 MPa and 455 ± 10 MPa due to the formation of nano-sized Al 2 Cu(Mg) precipitates, while the ductility remains fairly similar. [ABSTRACT FROM AUTHOR]

This investigation focusses on the influences of natural aging and repeated solution annealing on the microstructure and the mechanical properties of two different 7xxx Al-alloys. The alloys 7020 and 7175 were hot extruded and naturally aged at room temperature for 18 month. The strands were then analyzed in naturally aged condition and after three different repeated solution annealing processes. In a third step they were peak aged and then analyzed regarding their microstructure and mechanical properties. For the analysis of the microstructure a combination of optical, scanning and transmission electron microscopy as well as electron backscatter diffraction has been used. The mechanical properties were measured by compression and tensile tests. Several results can be concluded from these investigations: 1. The repeated solution annealing is affecting the grain morphology at the surface of the strands. 2. In alloy 7175 Al 2 CuMg and Al 12 Mg 2 Cr 2 particles were formed during the repeated solution annealing processes. 3. Specimens in the repeated solution annealed and subsequent peak aged condition exhibit lower tensile strength values than the naturally aged and subsequent peak aged alloys. 4. Neither repeated solution annealing nor natural aging is deteriorating the elongation at fracture of the peak aged material, which is a great advantage for the industry. [ABSTRACT FROM AUTHOR]

In the present paper, the influence of eutectic and intermetallic phases on cavitation resistance of Al-Si alloys was studied. In fact, Al-Si alloys are commonly used for the production of components, such as cylinders, pistons, pumps, valves and combustion chambers, which in service may incur in cavitation phenomenon. Samples of AlSi3, AlSi9 and AlSi9CuFe were characterized from the microstructural point of view. Hardness measurements were also performed. Subsequently, cavitation tests were carried out according to ASTM G32 standard and the erosion mechanism was examined by scanning electron microscope. It was found the both eutectic and intermetallic phases enhance cavitation resistance, expressed in terms of mass loss. Particularly, intermetallic particles with complex morphologies provide a positive contribution, exceeding that of other microstructural features, as grain size. The effect of T6 heat treatment was also evaluated. It was confirmed that the precipitation of fine strengthening particles in the Al matrix successfully hinders the movement of dislocations, resulting in a longer incubation stage and a lower mass loss for heat-treated samples in comparison with as-cast ones. Finally, the relationship between cavitation resistance and material hardness was investigated. [ABSTRACT FROM AUTHOR]

A combined preheating and oscillating arc process was carried out in narrow-groove butt joint welding to produce a defect-free weld joint containing a thick aluminum alloy section. The weld bead formation, welding defects such as lack of fusion and porosity, and the angular distortion of the weld joint were studied at various preheating temperatures in both a systematic experiment and a theoretical analysis. The microstructure characteristics of the weld joints produced at varying preheating temperatures were analyzed. The morphology of the β phase and its segregation behavior were observed in the region close to the lack of fusion and inter-pass of the weld deposit. The tensile strength of a sound welded joint with proper preheating reached 90% that of the base metal. [ABSTRACT FROM AUTHOR]

The results of microstructure examinations and studies of selected mechanical properties of four aluminium alloys used in the production of automotive air-conditioning ducts (AA3103, AA5049, AA6060, AA6063) before and after the ASTM G85:A3 SWAAT Test (SeaWater Acetic Acid Test) for corrosion resistance are presented. Materials used for the manufacture of such components should be temperature stable, and therefore thermal resistance tests were carried out in a wide range of temperatures, i.e., -25 °C, 25 °C, 40 °C, 60 °C, 80 °C, 100 °C, 140 °C, 180 °C, and 220 °C. Annealing was performed for 72 h and 240 h, followed by cooling in water. The obtained results have proved that the non-precipitation-hardenable AA3103 and AA5049 alloys remain stable in the entire range of the investigated temperatures. The measured microhardness of these alloys was 43-46 HV0.1 for AA3103 and 56-64 HV0.1 for AA5049. The microhardness of the 6xxx series aluminium alloys was not stable in the investigated range of temperatures. The maximum was observed in the temperature range of 100-140 °C, which corresponded to the precipitation process of intermetallic phases, as further confirmed by microstructure observations. After the corrosion test, the mechanical properties and elongation decreased by about 5-20%. [ABSTRACT FROM AUTHOR]

The plastic anisotropy of aluminium alloys is known to depend not only on the crystallographic texture but also on the heat-treatment, and this effect has been studied on various alloys both experimentally and numerically. However, the 6000 series of aluminium alloys is not broadly represented in these studies. In this work, an extruded profile of the AA6063 alloy was investigated. Electron backscatter diffraction (EBSD) measurements revealed a strong cube crystallographic texture with a minor Goss component, which is typical for recrystallized aluminium alloys. The plastic anisotropy was studied by uniaxial tension tests in different material directions, using digital image correlation to measure the displacement field and thus to calculate the strain field. The tensile specimens were heat-treated to three different tempers: T6, T7 and O, in addition to the as-received T1 condition. Transmission electronic microscopy (TEM) was used to characterize the precipitate structure of the heat-treated material. A crystal plasticity finite element model of the tensile test was created and calibrated using some of the experimental data. The comparison of the experimental stress-strain curves, strain ratios and flow stress ratios with their simulated counterparts revealed that the crystallographic texture is dominating the anisotropy in all tempers. The accuracy of the CP-FEM predictions varies for different material orientations, and, in general, the simulated material exhibits a sharper anisotropy than the real material. The effect of the heat treatment on the anisotropy is found to be minor compared with the texture effect. [ABSTRACT FROM AUTHOR]

Selective laser melting, a laser-based additive manufacturing process, can manufacture components with good geometrical integrity. Application of the selective laser melting process for serial production is subject to its reliability on mechanical properties, especially on fatigue behavior, when it is required to be applied for dynamic applications. This study focuses on microstructural, quasistatic, high cycle fatigue (HCF), and very high cycle fatigue (VHCF) mechanisms of aluminum alloys manufactured by selective laser melting. Manufacturing of hybrid structures by selective laser melting process is also investigated. Microstructural features were investigated for process-induced effects and the corresponding influence on quasistatic and fatigue properties. The microstructural features can be controlled in the selective laser melting process for required properties. Joining strengths in hybrid structures can be improved by post process heat-treatments. Material constants in different fatigue regions were determined, and higher fatigue strength of hybrid alloys was achieved in HCF as well as VHCF regimes. [ABSTRACT FROM AUTHOR]

In this paper, the sequence of solidification for A380-type alloys has been determined by employing techniques such as dilatometry, differential scanning calorimetry (DSC), and differential thermal analysis (DTA). Regions of balance of Cu- and Fe-rich phases present in the alloys were calculated using Thermo-Calc software, and the results indicate that the phenomena that occur during solidification are modified by differences in the purity of the alloys. The effect of heat treatment on the morphology and chemical composition of the Fe-, Mg-, Mn-, and Cu-rich intermetallic species were obtained. For a ratio of Fe-Mn < 1, it was observed that intermetallic AlFeMn begins its formation in the liquid state, precipitating with a needle-like shape. The temperatures of formation of these intermetallic phases in the solid state were identified by DSC and DTA analysis. It was found that changes in the chemical composition (relative concentrations of Fe, Mn and Si) affect the formation of the α-AlFeMnSi phase during heat treatment. [ABSTRACT FROM AUTHOR]

The aim of the current study was to examine the structure of an alloy treated at various temperatures up to 2,000-2,100 °C. Among research techniques for studying alloy structure there were the electron and optical microstructure, X-ray structure, and spectral analysis, and for studying the developed furnace geometric parameters the authors employed mathematical modeling method. The research was performed using aluminum smelting gas-fired furnaces and electric arc furnaces. The objects of the study were aluminum alloys of the brand AK7p and AK6, as well as hydrogen and aluminum oxide in the melt. For determining the hydrogen content in the aluminum alloy, the vacuum extraction method was selected. Authors have established that treatment of molten aluminum alloy in contact with carbon melt at high temperatures of 2,000-2,100 °C has resulted in facilitating reduction of hydrogen and aluminum oxide content in the melt by 40- 43% and 50-58%, respectively, which is important because hydrogen and aluminum oxide adversely affect the structure and properties of the alloy. Such treatment contributes to the formation of the extremely fine-grained microstructure of aluminum alloy. [ABSTRACT FROM AUTHOR]

In this work, a fine-grained structure with a uniform distribution of TiB2 particles and precipitates was achieved in TiB2 particle-reinforced (PR) Al-Zn-Mg-Cu alloys by friction stir processing (FSP). The effects of multi-pass FSP on the microstructure, and TiB2 particle distribution, as well as the microstructural evolution in the following T6 treatment, were investigated by X-ray diffraction, scanning electron microscopy and associated electron backscattered diffraction. The results showed that the distribution of TiB2 particles and alloy precipitates was further improved with an increase in the FSP passes. Moreover, compared with alloy segregation in the as-cast PR alloys during T6 treatment, a complete solution of the precipitates was achieved in the FSP-treated PR alloys. The fine-grained structure of the FSP-treated PR alloys was thermally stable without any abnormal growth at the high temperature of T6 treatment due to the pinning effect of dispersed TiB2 particles. The strength and ductility of the PR alloys were simultaneously improved by the combination of FSP and T6 treatment. [ABSTRACT FROM AUTHOR]

This work presents the characterization of Al-6Si-3Cu-xMg (x = 7, 9 and 11 wt%) foams obtained through the in-situ process. Heat treatments which consisted on over-heating the alloys during 6 h at 520, 560 and 600 °C were performed. The microstructural changes, the quantification and measurement of sizes and shapes of second phases and pores were carried out by means of Optical Microscopy (OM), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Compression tests and density measurements were also assessed. The results showed porosities ranging from 2 to 40%, with pore sizes from 20 to 150 μm, shape factors from 0.59 to 0.72, and maxima relative densities between 0.89 and 0.91. The formation of these pores was attributed to the dissolution and melting processes of the second phases and the shrinkage originated after their solidification. Fragmentation, spheroidization and coarsening of second phases during the solution heat treatment was also observed. It was found that the microstructures of the foams, including pores and second phases, strongly depended on the over-solution temperature and the Mg content. Temperature was the manufacturing variable that most affected the size and quantity of the pores produced. [ABSTRACT FROM AUTHOR]

Friction Stir Welding (FSW) is a solid-state welding process, based on frictional and stirring phenomena, that offers many advantages with respect to the traditional welding methods. However, several parameters can affect the quality of the produced joints. In this work, an experimental approach has been used for studying and optimizing the FSW process, applied on 5754-H111 aluminum plates. In particular, the thermal behavior of the material during the process has been investigated and two thermal indexes, the maximum temperature and the heating rate of the material, correlated to the frictional power input, were investigated for different process parameters (the travel and rotation tool speeds) configurations. Moreover, other techniques (micrographs, macrographs and destructive tensile tests) were carried out for supporting in a quantitative way the analysis of the quality of welded joints. The potential of thermographic technique has been demonstrated both for monitoring the FSW process and for predicting the quality of joints in terms of tensile strength. [ABSTRACT FROM AUTHOR]

The microstructure, electrical conductivity and mechanical properties of cast Al-2Li-2Cu-0.5Mg-0.2Zr alloy during heat treatment were investigated. The results indicated that a population of secondary phases enriched along grain boundaries in as-cast studied alloy, most of which dissolved into the α-Al matrix after solution treatment. Profound enhancement in mechanical properties of the studied alloy was obtained after T6 heat treatment. TEM observations revealed competitive precipitation of T 1 (Al 2 CuLi) and S′ (Al 2 CuMg) phases during ageing, while no θ′ (Al 2 Cu) phase was observed. The anomalous decrease in conductivity observed during ageing was attributed to the precipitation of T 1 phases. Fine δ′ (Al 3 Li) particles were homogeneously distributed after quenching, gradual coarsening of which was observed with prolonged ageing time. As ageing proceeded, the δ′ coarsened and δ′-Precipitate-Free Zones (PFZs) developed, resulting in diminishing ductility observed from as-quenched to peak-aged state. Precipitation and continuous coarsening of T 1 phases kept on at the expense of gradual δ′ dissolution. The improvements of ductility observed in over-aged samples arose mainly from the presence of T 1 , S′ phases, Al 3 (Li,Zr) composite precipitates and progressive δ′ dissolution. Moreover, continuous coarsening of T 1 and S′ phases contributed primarily to the strength loss in over-aged studied alloy. [ABSTRACT FROM AUTHOR]