A Review on Friction Stir Welding of High-Strength Al-Zn-Mg Alloy: Insights on Second-Phase Particles.

The friction stir welding (FSW) process is a unique combination of deformation and high temperature, which provides opportunities to modify microstructures through the adjustment of the processing parameters and is an ideal way to join non-weldable aluminum alloys by avoiding the formation of a molten pool. The 7xxx series heat-treatable aluminum alloys are widely used in the aerospace field as high-performance structural materials. The microstructure evolution and mechanical performance of these alloys are affected by the effects of thermomechanical processing, which provides opportunities to optimize the material properties by controlling microstructural features such as intermetallic constituent particles, dispersoids and nanoscale precipitates.

Prediction of new spin-forbidden transitions in the N molecule-the electric dipole A'Σ → AΣ and magnetic dipole a'Σ ← AΣ transitions.

On the ground of multi-reference configuration interaction calculations with an account of spin-orbit coupling, we have predicted the probability of two unknown spin-forbidden transitions in the spectrum of the N molecule: the electric dipole A'Σ → AΣ emission system and the magnetic dipole a'Σ ← AΣ transition. The radiative lifetime of the lowest A'Σ sublevel is less than a microsecond; the magnetic transition induced by the spin current in the triplet state is predicted with relatively low oscillator strength (f = 10), which still could be detectable.

Triplet state harvesting and search for forbidden transition intensity in the nitrogen molecule.

Triplet excited states of the N molecule play an important role in electric discharges through air or liquid nitrogen accompanied by various afterglows. In the rarefied upper atmosphere, they produce aurora borealis and participate in other energy-transfer processes connected with atmospheric photochemistry and nightglow. In this work, we present spin-orbit coupling calculations of the intensity of various forbidden transitions, including the prediction of the electric dipole transition moment of the new band, which is strongly prohibited by the (+|-) selection rule, the new spin-induced magnetic transition, magnetic and electric quadrupole transitions for the BΠ Wilkinson band, and the Lyman-Birge-Hopfield aΠ ← XΣ transition.

Composition of Organosilicate Coatings High-Temperature Breakdown Products and Their Distribution in the Weld.

The construction assembly and the repair of steel constructions painted with protective coatings are often carried out using arc welding. During the welding process, the coating in the weld zone is degrading. The protective coatings breakdown products are involved in the pore and non-metallic inclusion formation in the weld, the composition and distribution study of which makes it possible to analyze the reactions occurring during the welding.

Effect of Different Tool Probe Profiles on Material Flow of Al-Mg-Cu Alloy Joined by Friction Stir Welding.

Friction Stir Welding (FSW) was utilized to butt-join 2024-T4 aluminum alloy plates of 1.9 mm thickness, using tools with conical and tapered hexagonal probe profiles. The characteristic effects of FSW using tools with tapered hexagonal probe profiles include an increase in the heat input and a significant modification of material flow, which have a positive effect on the metallurgical characteristics and mechanical performance of the weld.