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In the present study, the PLC characteristic parameters and DSA mechanism of Al-(2.86~9.41) Mg alloy sheets were investigated during tensile testing at room temperature with a tensile rate of 1 × 10−3 s−1. On the basis of the solution Mg concentrations in the α-Al matrix, the initial vacancy concentration, the second-phase particle configuration and the recrystallized grain configuration are almost the same by quenching treatment. The results show that the type of room-temperature tensile stress–strain curves of quenched Al-(2.86~9.41) Mg alloy sheets varied according to the Mg content. The type of stress–strain curve of the Al-2.86 Mg alloy sheet was B + C, while the type of stress–strain curve of the Al-(4.23~9.41) Mg alloy sheets was C. When the quenched Al-(2.86~9.41) Mg alloy sheets were stretched at room temperature, the strain cycle of the rectangular waves corresponding to the high stress flow Δ ε T max and stress drop amplitude Δ σ on the zigzag stress–strain curve of alloy sheets increased with increasing the Mg content. Moreover, the strain cycle of Δ ε T max and Δ σ on the stress–strain curve of alloy sheets increased gradually with increasing tensile deformation. The yield stress of quenched Al-(2.86~9.41) Mg alloy sheets increased gradually with increasing the Mg content. Moreover, the critical strain corresponding to yield stress ε σ and the critical strain corresponding to the occurrence of the PLC shearing band ε c of alloy sheets both increased with increasing the Mg content. However, the difference in flow strain value Δ ε c − σ between ε c and ε σ of alloy sheets decreased gradually with increasing the Mg content. [ABSTRACT FROM AUTHOR]

The stress-strain flow curves of solid solution treated and annealed Al-(2.86-9.41)Mg aluminum alloy sheets were investigated during tensile process at room temperature at a strain rate of 1 × 10−3 s−1, in order to reveal the effect of solute Mg atoms and β-phase nanoparticles in the α-Al matrix on their Portevin-Le Chatelier (PLC) characteristics. The results show that with the increase of Mg contents of alloys, the concentration of solute Mg atoms and the volume fraction of β-phase nanoparticles in the α-Al matrix of the annealed alloy sheets increase. The β-phase nanoparticles promote the PLC effect during the tensile process, causing the increase of stress drop amplitude Δ σ of the tensile curves of the alloy sheets. However, the β-phase nanoparticles have little influence on the strain period Δ ε T max of rectangular waves. The flow strain difference Δ ε c − σ between the yield point and the beginning of PLC effect decreases monotonically from 5.4 × 10−4 to 5 × 10−5 as the Mg contents of alloy sheets increase from 2.86 wt.% to 9.41 wt.%. The strain period Δ ε T max of the rectangular waves corresponding to the high flow stress and stress drop amplitude Δ σ obtained for the serrated stress-strain curves of the alloy sheets gradually increase with the increasing Mg contents of alloy sheets. • The effects of both solute Mg content and β-phase nanoparticles on the PLC characteristics of annealed Al-(2.86-9.41 wt.%) Mg alloy sheets were studied quantitatively. • The β-phase nanoparticles really promote the PLC effect of annealed Al-(2.86-9.41 wt.%) Mg alloy sheets, which increase the stress drop amplitude Δ σ of the tensile curves. However, β-phase nanoparticles have little influence on the strain period Δ ε T max of the rectangular waves. • The flow strain difference Δ ε c − σ between the yield point and the beginning of PLC effect decreases monotonically from 5.4 × 10−4 to 5 × 10−5, as the Mg content of alloy increases from 2.86 wt.% to 9.41 wt.%. [ABSTRACT FROM AUTHOR]

Abstract: Ultrasonic welding between SS400 mild steel sheet and aluminum alloy sheet containing magnesium (A5052) was conducted. In this study, authors investigated the influence of ultrasonic welding conditions on the mechanical properties and the interface microstructure of a joint, and the effect of insert metal was examined to improve the joint strength. The main results obtained in this study are as follows. It was possible to weld ultrasonically SS400 mild steel sheet to A5052 aluminum alloy sheet containing magnesium. The strength of the joints welded using various clamping forces and constant welding time of 1.0s showed the maximum value at the clamping force of 588N and decreased with the clamping force over 588N because the excessively large clamping force reduced the frictional action at the interface. The strength of the joints welded using the constant clamping force of 588N and various welding times showed the maximum value at the welding time of 2.5s. However, the strength of the joint welded using the welding time of 3.0s decreased due to the formation of Fe2Al5 intermetallic compound at the interface. Using the insert metal of commercially pure aluminum, the joint strength was successfully improved and the strength of the welded using 3.0s welding time was about three times as large as that of the joint without the insert metal. [Copyright &y& Elsevier]

The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al-Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al-Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al-Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF6) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al-Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions. [ABSTRACT FROM AUTHOR]

Warm press forming of aluminum alloy sheets is quite attractive, since undesirable stretcher strain marks, which often appear on the surface of the sheets during cold press forming, will disappear at high temperature, and furthermore, some aluminum alloys exhibit high-temperature superplasticity at a certain forming speed. In order to determine the optimum condition of press forming for an aluminum alloy sheet, the effect of forming temperature on the yield locus was experimentally investigated. The yield locus for a fine-grain Al–Mg alloy (5083-O) sheet was obtained by performing biaxial tensile tests, using cruciform specimens, at temperatures of 30, 100, 170, 250 and 300 °C at strain rate of 10 s−1. The size of yield locus drastically decreased with increasing temperature. Neither von Mises’ criterion or Hill’s can well predict the shape of the yield locus of this sheet metal. Instead of these quadratic yield functions, the yield criterion of Logan–Hosford or Barlat is a better choice for the accurate description of biaxial stress–strain responses at a high temperature. [Copyright &y& Elsevier]