Three different bonding couples assembled by two commonly used aerospace aluminum alloys were bonded within the temperature range of 460–520 °C under 6 MPa for 60 min in vacuum atmosphere. The interface microstructure and alloying elements distribution of the bonded joints were determined by scanning electron microscope (SEM) and Energy Dispersive Spectroscope (EDS); the bond strength was evaluated by tensile-shear strength test. The results show the bond quality improved effectively as the bonding temperature increased. Compared with the 1420-1420 and 7B04-7B04 bonding couples, the 1420-7B04 couples obtained better interface integrity and higher bond strength, the highest shear strength for 1420-7B04 couple can be as high as 188 MPa when bonded at 520 °C. Special attention was focused on the 1420-7B04 couple, the diffusion coefficient of Mg at the original interface under different temperatures were investigated, the results show the diffusion coefficient increased obviously as the bonding temperature increased. A diffusion affected zone (DAZ) without continuous intermetallic phases formed due to the diffusion of alloying elements across the bonding interface. The combined action of temperature and alloying elements gradient resulted in the increase of alloying elements diffusion fluxes, which in turn promote the bonding quality through the accelerated shrinkage of interfacial voids.

The Al–Li alloy is becoming popular for aerospace application owing to their low density, high specific strength, good corrosion resistance, etc. The diffusion bonding/superplastic forming (DB/SPF) structure of titanium alloy has been widely used in the aerospace industry. In order to broaden the application of Al–Li alloy, it is necessary to develop its diffusion bonding and superplastic forming (DB/SPF) technology. In the present study, diffusion bonding of 1420 Al–Li alloy assisted by pure aluminum foil was conducted on Gleeble-3500 thermal simulation system under different bonding parameters, the results show that the bonding temperatures have direct influence on the interface microstructure and bond strength of joints. Meanwhile, when the pure aluminum interlayer was introduced into the diffusion bonding process, the alloying element diffusion across the bond can improve the interface integrity and the mechanical properties. The joint formation mechanism with interlayer was investigated in detail, the development and application of this method was explored.

Selective laser melting was recently introduced to fabricate complex parts that are likely to contain overhangs. Process parameters, scanning strategies, support structures, and fast prediction techniques are being frequently studied, but little information about overhang forming direction has been reported. In this study, the effects of overhang forming direction in the working plane on temperature evolution and distortion processes during selective laser melting of Ti-6Al-4V alloy were examined by means of numerical simulation and experimental verification. We found that forming from different directions can lead to significant differences in the early stage of the overhang building process, which were verified by both the simulations and the experiment. Some analyses were performed when enough layers had been built and suggestions are also given.

Advanced aerospace alloy deformation processing (contribution 1–3) is investigated in this collection

High-entropy diboride-based (MeB₂-based) ceramics are promising high-temperature structural materials because of their excellent mechanical properties, high-temperature stability, and oxidation resistance. In order to achieve low-temperature sintering of the high-entropy ceramics, a novel preparation method of high-entropy (Ti,Zr,Nb,Mo,W)B₂-SiC ceramics based on reactive sintering of pre-alloyed solid-solution metals and nonmetals of Si, C, B₄C was conducted in the current work. Mechanical alloying behavior of the mixed metal powders, as well as the phase composition, microstructure, mechanical properties, and oxidation behavior of the as-sintered MeB₂-SiC ceramic were investigated. The XRD, SEM, and EPMA results indicated that the primary MeB₂ solid-solution and SiC phases could be successfully formed during reactive sintering at a relatively low temperature of 1650 °C. The as-sintered MeB₂-SiC ceramics had a high relative density of 97.8% and high mechanical properties (hardness of 19.74 ± 0.8 GPa, flexure strength of 533 ± 38 MPa, and fracture toughness of 6.01 ± 0.77 MPa·m^1/2). Combining the oxidation behavior and microstructure evolution of the oxidation layer, a continuous and relatively dense MeO_x-SiO₂ oxidation layer was gradually formed and covered on the external surface, leading to decelerating oxidation behavior after an oxidation exposure time of 10 min.