This article presents cyclic hardening/softening behaviors (experimental data) of the heat-treated aluminum-matrix nano-clay-composite (AlSi_N_HT6), compared to those of the piston aluminum alloy (AlSi) under strain-controlled loading. For such an objective, standard samples were fabricated by gravity and stir-casting methods. Low-cycle fatigue experiments were carried out under different strain amplitudes (0.20–0.45%) and at various temperatures (25–300°C). Obtained results implied that no obvious change was observed on material properties of aluminum alloy by reinforcements, but a decrement was observed due to increasing the temperature. Results also indicated that the increase of the temperature from 25°C to 200°C has changed the cyclic behavior of both materials (AlSi_N_HT6 and AlSi) from hardening to softening. Moreover, the temperature effect was more significant than the total strain amplitude influences in cyclic behaviors.

Mo, Zr, and Y with low diffusion coefficients in Al matrix were used to improve the high-temperature properties of the Al–5.8Cu–0.3Mn–0.2Mg alloy. The effects of these microalloying elements on the microstructures of the Al–5.8Cu–0.3Mn–0.2Mg alloy were investigated with the aid of optical microscopy and high-resolution transmission electron microscope (HRTEM). The HRTEM images and selected area electron diffraction patterns indicated that L12-Al3(Zr, Y), Al3Zr, Al3Y, and Al12Mo could precipitate in the process of solid solution treatment after adding Mo, Zr, and Y. These Mo-, Zr-, and Y-containing precipitates were stable at high temperatures and could slow the coarsening rate of θ′ precipitates at high temperatures. The tensile strength of the Al–5.8Cu–0.3Mn–0.2Mg alloy modified by Mo, Zr, and Y microalloying elements was improved significantly at both room and high temperatures. The strengthening mechanisms were discussed in detail.

Effects of varying volume fractions of SiC nanoparticle (SiCNP) reinforcement on microstructure and mechanical properties of dissimilar AA2024-T351 and AA7075-T651 joints by friction stir welding (FSW) have been investigated experimentally. A rectangular section edge groove was prepared at the adjoining surfaces of the two plates with the butt configuration before FSW. Initially, four fractional volumes with 0, 5, 8, and 13% of SiCNP are reinforced into the grooves of width, 0, 0.2, 0.3, and 0.5 mm and the FSW was performed with the first and second pass to obtain metal matrix nanocomposite (MMNC) at the weld nugget zone (WNZ). The characterization of microstructure specimens was investigated using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction technique (XRD). The FSW joint specimen produced with 5 vol% fraction of SiCNP for second pass processing observes a defect-free, homogeneous distribution of SiCNP with a mean grain size of about 2–3 µm at the WNZ and weld joints higher in tensile strength, 411 MPa, yield strength, 252 MPa, and percentage elongation, 14.3. The result shows that varying volume fractions (5, 8, 13%) of the SiCNP after the FSW second pass led to significant grain refinement at the WNZ and higher mechanical properties compared with FSW specimens prepared without SiCNP. Higher hardness of 150 Hv was observed in the WNZ for specimen produced with 13 vol% fraction SiCNP.

5xxx series aluminum alloys, as Al-4.5Mg-1.0Mn (AA5083), are strengthened by Mg solid solution and work hardening. A drawback of this alloy is the fact that β phase, Al3Mg2, can precipitate on grain boundaries causing sensitization and intergranular corrosion, which is detrimental to the integrity of the structure. Metallography is an important technique to study the grain structure and highly sought for intergranular corrosion evaluation; however, revealing the grains of completely un-sensitized AA5083 is challenging. This paper introduces a new procedure to etch AA5083 samples that were solutionized at 450°C for 1.5 h. The new procedure is a two-step etching method, including a phosphoric acid pre-etching step and a Weck’s reagent coloring step. Solutionized, lightly sensitized, and as-received AA5083 were evaluated, and the grains were observed using optical microscopy. The microetching mechanism was further studied by optical profilometry, atomic force microscopy, scanning electron microscopy, and energy dispersive spectrometry. The phosphoric acid created a surface profile determined by the grain orientations and its reactivity, and the Weck’s reagent was then able to color grains by preferential MnO2 formation over some pre-etched grains. Moreover, the final polishing with colloidal silica was essential to reach a high contrast image.

TiB2 particulates were formed in situ in an aluminum matrix via chemical reactions between an aluminum melt and the mixture of K2TiF6 and KBF4 salts. Different effects of Sc addition on the formation of the TiB2 particulates were revealed depending on the participation of Sc at different stages of the formation of the particulates. The metal–salt reactions resulted in boride layers along the α-Al grain boundaries in the presence of Sc, while the addition of Sc after the metal–salt reactions broke up the boride layers improving the dispersion of the TiB2 particulates to a limited degree. Sc promoted the growth of the TiB2 particulates, resulting in the coarsening of TiB2 particulates. The participation of Sc in the formation of TiB2 particulates altered the coarsening of the TiB2 particulates, resulting in different morphologies of the TiB2 particulates depending on the participation of Sc in the formation of the TiB2 particulates at different stages.

The effect of aging time on the corrosion behavior of 6005 Al alloys has been investigated in aerated 3.5% NaCl aqueous solution. The corrosion resistance of the alloy with different aging times is analyzed by measuring potentiodynamic polarization, electrochemical impedance spectroscopy. The surface morphology is examined by scanning electron microscopy. The results demonstrated that the corrosion resistance of the alloy in the peak-aged condition is worse than the other conditions. Accordingly, corrosion rate and the corrosion current density of the alloy reach its maximum value. An Fe-rich phase is identified as the β-Al4.5FeSi phase by atomic-resolution high angle annular dark field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy mapping analyses. The β-Al4.5FeSi is wrapped slowly by the precipitates of Mg2Si from the process of the peak-aged condition to the over-aged condition. It is hypothesized that the change of corrosion behavior of the alloy may be attributed to the β-Al4.5FeSi wrapped slowly by the precipitates of Mg2Si.

The aim of this study is to investigate the effects of different master alloys containing Ti, B, and Zr on the structure and tensile properties of thin-section A356 aluminum alloy in as-cast and T6-treated conditions. Microstructural examinations were performed using light optical and scanning electron microscopy. The results showed that the addition of 0.1 wt% Ti, 0.05 wt% B, and 0.1 wt% Zr decreases the average grain size of the cast alloy from 840 μm to 387 μm, 236 μm, and 363 μm, respectively. This structural refinement results in the variation of the α-Al primary phase distribution mode from dendritic to rosettelike. It has been found that 0.6 wt% Al–8B master alloy (0.05 wt% B) is the strongest to refine the structural parameters. This leads to the enhancement of both ultimate tensile strength and elongation values from 208 MPa and 6.2% in as-cast to 290 MPa and 12.5% in B-refined alloy at T6-treated conditions. In addition, the presence of more fine dimples on the fracture surfaces of the T6-treated specimens revealed that T6-treatment encourages ductile mode of fracture.

The orientation relationship (OR) between Al matrix and several typical inclusions, Al2O3, MgO, AlN, TiB2, and AlB2, in Al alloy have been studied by edge-to-edge matching model and refined with Δg theory. Based on the calculation of interatomic spacing misfit and interplanar spacing misfit, the number of ORs between Al and Al2O3, MgO, AlN, TiB2, AlB2 were predicted to be 1, 7, 2, 2, and 2, respectively. The result reveals that the wettability of Al to the studied inclusions could rank as MgO, AlB2, TiB2, AlN, Al2O3 in the order of decreasing, and the removability of those particles from aluminum melt rank in an opposite way from the perspectives of crystallography features of interfacial energy. Moreover, Al2O3 have a higher sensitivity to the performance of a processed aluminum alloy component than other inclusions, and MgO has the minimal impact, when the studied inclusions were residual in aluminum alloy.

Recently, cold metal transfer (CMT) process has been successfully applied to weld dissimilar metals. In this paper, two different aluminum alloy AA6061-T6 and pure copper T2 lapped joints were performed by CMT with AA4043 aluminum alloy wire as the filler metal. Results indicated that sound lapped joints between aluminum alloy AA6061-T6 and pure copper T2 could be performed by CMT technology. The joint was composed of Al–Al welding joint and Al–Cu brazing joint. The Al–Al welding joint was formed between the Al weld metal and the Al base metal, and the weld metal in Al–Al welding joint was composed of α-Al solid solution, α-Al, and CuAl eutectic phase. Al–Cu brazing joint was formed between the Al weld metal and the local molten Cu base metal, and composed of three copper-weld metal interfaces with a large amount of intermetallic compounds (IMCs), i.e., CuAl2, CuAl. The optimum strength of two joints could reach up to 1.23 kN and 1.56 kN, respectively, which was mainly due to the differences of the size of Cu/Al IMCs and stress condition. In addition, the distribution of microhardness and fracture surface of two joints were observed and analyzed in detail.

The effects of stress-aging processing on corrosion resistance of an Al–Zn–Mg–Cu alloy were investigated. It is found that the one-stage stress-aged alloy is strongly sensitive to the electrochemical corrosion. The poor corrosion resistance of the one-stage stress-aged alloy can be attributed to fine intragranular aging precipitates and continuous distribution of grain boundary precipitates. Meanwhile, the incomplete precipitation of solute atoms results in high electrochemical activity of aluminum matrix. However, when the alloy is two-stage stress-aged, the corrosion resistance is greatly improved. Furthermore, the corrosion resistance decreases firstly and then increases with increasing the first stage stress-aging temperature. Increasing external stress can enhance the corrosion resistance of the two-stage stress-aged alloy. These phenomena are mainly related to aging precipitates within grains and along grain boundaries. The coarse and relatively low-density intragranular aging precipitates, as well as the discontinuously distributed grain boundary precipitates can enhance the corrosion resistance of the stress-aged alloy.

The mechanical response of materials under repeated impact loading is of primary importance to model different types of surface mechanical treatments, such as shot peening. A reverse identification method of stress–strain curves using repeated impact has been developed by Kermouche et al. [Kermouche et al., Mater. Sci. Eng., A569, 71–77 (2013)] and later improved by Al Baida et al. [Al Baida et al., Mech. Mater.86, 11–20 (2015)]. This study deals with the experimental validation of this method on three materials: a home-made pure iron, a commercially pure copper, and an industrial aluminum alloy. An approximate method derived from cone indentation theory to check the reverse method reliability. Balls of different sizes have been used to cover a wide enough range of strain. The results are also compared with macroscopic compression and traction tests. The effect of the strain rate on the stress–strain curve is discussed. The conclusion section highlights the rapidity and the ease of use of the reverse identification method.

Nanobelt-like precipitates in an Al–Si–Mg–Hf alloy were studied using electron backscattered diffraction (EBSD) and focused ion beam (FIB) scanning electron microscopy techniques. One grain of the Al matrix with a near [111] normal direction was identified by EBSD and the three-dimensional (3D) microstructure of nanobelt-like precipitates in this grain was studied using 3D-FIB. Ten growth directions of the nanobelt-like precipitates in the grain were identified.

High performance die castings are urgently expected to be used as structural components subjected to dynamic loading. Therefore, tensile properties, fatigue, and corrosion-fatigue behavior of automotive die cast AlMg5Si2Mn alloy are studied in the current work. The results indicate that the tensile strength and yield strength of the as-cast specimens are obviously lower than those of the age-treated specimens, while the elongation decreases with increasing aging time. Neutral corrosive environment (3.5% NaCl solution) dramatically decreases the fatigue limits from 75 to 50 MPa. Fatigue lives of the directly corroded and precorroded specimens are close to each other. The values of material constants m and C are in the range of 5.756–5.874 and 2.421 × 10−10 to 4.285 × 10−9, respectively. Obscure fatigue striations and featureless facets are observed in crack propagation regions. Anodic dissolution is dominantly responsible for the premature crack initiation and stress corrosion cracking leading to the formation of fractured α-Al matrix.

A comprehensive understanding of the growth pattern of intermetallic compounds (IMCs) during solidification is critical to both the crystal-growth theory and its property optimization. In this article, growth pattern and three-dimensional (3D) morphology of primary Al6Mn IMC were investigated in directionally solidified Al–3 at.% Mn alloy at a wide range of growth rates. A transition from faceted (<60 μm/s) to nonfaceted growth (>100 μm/s) was observed with increasing growth rates. Correspondingly, 3D morphologies of primary Al6Mn change from a solid polyhedron to a hollow structure, and then to a dendrite. This kind of change is associated with the competitive growths of different crystal planes determined by the crystallographic anisotropy and growth kinetics of Al6Mn. A growth model based on atomic cluster attachment is proposed to reveal the growth transition, and a growth-rate ratio between different crystal planes is used to appropriately reveal the formation mechanism of different morphologies at low rates.

High strength aluminum (Al) alloys were prepared by rapid solidification method in the Al–Ni–La system. Microstructural characterizations show that all the investigated Al–Ni–La alloys are comprised of Al, rod-like Al3Ni, and blocky Al11La3 phases, of which the size and volume fraction are composition-dependent. The Al85.5Ni9.5La5 (at.%) alloy shows the finest microstructure, which contributes to the highest strength along with considerable plasticity. The experimental analysis and finite element simulation (FES) show that the distribution of the intermetallic phases greatly affects the mechanical properties of the alloys. The rod-like Al3Ni phase precipitated with the locally uniform direction prevents the propagation of cracks and benefits the plastic deformation, whereas the blocky Al11La3 phase exhibits the nature of brittleness and acts as the origin of the microcrack initiation. These findings suggest a new method to design high strength Al alloys.

Aluminum-lithium alloys are widespread in the aerospace industry. The new 2099 and 2199 alloys provide improved properties, but their microstructure and texture are not well known. This article describes how state-of-the-art field-emission scanning electron microscopy (FE-SEM) can contribute to the characterization of the 2099 aluminum-lithium alloy and metallic alloys in general. Investigations were carried out on bulk and thinned samples. Backscattered electron imaging at 3 kV and scanning transmission electron microscope imaging at 30 kV along with highly efficient microanalysis permitted correlation of experimental and expected structures. Although our results confirm previous studies, this work points out possible substitutions of Mg and Zn with Li, Al, and Cu in the T1 precipitates. Zinc and magnesium are also present in “rice grain”–shaped precipitates at the grain boundaries. The versatility of the FE-SEM is highlighted as it provides information in the macro- and microscales with relevant details. Its ability to probe the distribution of precipitates from nano- to microsizes throughout the matrix makes FE-SEM an essential technique for the characterization of metallic alloys.

An important metallurgical difficulty in arc welding of high-strength aluminum alloys isformation of solidification cracking. In this work, an attempt is made to reduce thesolidification cracking in welding of aluminum alloys through vibratory treatment. Thematerial used for the investigation is AA2014 aluminum alloy, which is highly prone tosolidification cracking. Vibratory treatment was carried out in the frequency range of 100Hz to 3700 Hz. Weldments made with and without vibratory treatment were compared usingweld cracking tests and other characterization tests such as microstructural analysis. Thetest results show that by applying vibratory treatment, solidification cracking can belargely controlled in arc welding.

6201 aluminum alloy is mostly used in electrical conductors for overhead transmission lines due to its excellent mechanical and electrical properties besides to an excellent corrosion resistance. This alloy is heat treatable and the thermal treatment is performed with the objective of obtain the optimal properties for its application. In this work it was studied the effect of different deformation grades, time variation of natural aging as well as the time and temperature of artificial aging on the evolution of mechanical and electrical properties. It was found that solution treated wires at 560°C by 4h, 14 days natural aged, 92% cold deformed and artificial aged at 165°C by 7h, reach a tensile stress of 326 MPa and an electrical conductivity of 57.2%IACS (International Annealed Copper Standard).