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Age-hardenable 2000- and 7000-series aluminium alloys share the ability to achieve outstanding combinations of high specific strength and fracture toughness without including expensive alloying elements such as scandium. Using laser surface melting (LSM), we investigate the suitability of two commercial, high-strength aluminium alloys (ultimate tensile strength ≥ 600 MPa) for laser powder bed fusion (L-PBF). It is revealed that solidification cracks form in both, the third-generation Al-Cu-Li alloy 2065 and the high-Zn containing alloy 7034, with the latter having a lower crack density. Through a combination of microstructural characterisation by SEM, EDS, and EBSD, residual stress analysis and quantitative hot cracking criteria, we deduce that alloy 2065 shows greater potential for L-PBF application despite its slightly higher crack density after LSM. Through laser surface alloying, the composition of alloy 2065 was systematically varied in terms of titanium and copper content to improve its cracking resistance. It is found that the formation of solidification cracks is suppressed by the addition of 2 – 4 wt% Ti, whereas the introduction of copper has little effect. Our study suggests that Ti-modified 2065 is an attractive alloy for L-PBF. It could potentially join the existing high-strength aluminium feedstock materials available for L-PBF. [Display omitted] [ABSTRACT FROM AUTHOR]

The influence of homogenisation annealing process on microstrucure of 7085 Al alloy has been investigated by optical microscopy(OM), scanning electron microscopy combined with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction(XRD), and differential scanning calorimetry (DSC). The results show a large amount of skeletal Mg(Zn, Al, Cu)2 phase and AlZnMgCu phase distributed as eutectic microstructure on crystal boundaries, and some impurity phase of triangle or square Al18Mg3Cr2 in the interior of grain in as-cast 7085Al alloys. In combination with DSC and OM observation, the temperature of homogenisation annealing is determined lower than 473°C. With increasing temperature of homogenising annealing, the woven crystal microstructure on the grain boundary and part lager block second phase in interior of grain decreases, and grain boundary turns to be discontinuous. 7085Al alloys are treated by homogenising annealing of 470°C/24 h, grain boundary turns to be discontinuous, uniform and fine precipitation phase arises, and woven eutectic microstructure and lager block second phase disappear. The optimised homogenising annealing is 470°C/24 h in the study. [ABSTRACT FROM AUTHOR]

Al-Ti-Zr ternary system with different compositions (Al 40, 41, 43, 50 at.%) was synthesized by in-situ reaction of ZrH 2 , TiH 2 and Al powders through vacuum hot pressing at 1400 °C for 0.5 h under 40.8 MPa. The microstructure, micro hardness, fracture toughness, and flexural strength of Al-Ti-Zr alloys were investigated. AlTi 2 + TiAl and Zr(Ti)Al + Al 3 (Ti, Zr) 5 new lamellar structures were found in the samples. Micro hardness increased while flexural strength and fracture toughness decreased with the increasing of the ratio of Al-Zr intermetallics. Flexural strength and fracture toughness of Al43 were the highest reaching up to 396.0 MPa and 6.0 MPa.m 1/2 , respectively. The fracture modes of Ti 3 Al + TiAl, AlTi 2 + TiAl and Zr(Ti)Al + Al 3 (Ti, Zr) 5 lamellar structures were transgranular fractures, while fracture modes of Al-Zr intermetallics were intergranular fractures. The crack tip blunting and the effect of crack deflecting in Ti 3 Al + TiAl lamella led to increasing of flexural strength and fracture toughness. Besides, interlayer tearing of the three lamellar structures led to rising of flexural strength. [ABSTRACT FROM AUTHOR]

The present investigation is mainly focused on friction stir additive manufactured (FSAM) 2195 Al-Li alloy in aspects of localized microstructure evolution and mechanical performance. Characterization of the localized microstructure was conducted by optical microscope (OM), electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM) techniques, and mechanical properties were evaluated based on micro-hardness and tensile testing measurements. Results showed a build of multilayered stack of 2195 aluminum lithium alloy was fabricated using FSAM via multi-pass processing. Defects such as voids or kissing bond were not identified, and fine equiaxed grains were observed in the nugget zone (NZ). The decrease of average grain size and low angle boundaries (LABs) along the depth of the NZ was attributed to repetitive stirring action of the rotating tool. Distribution of precipitation phase is mainly determined by the thermal cycle. Numerous T 1 and θ ′ precipitates were identified in the base material (BM), which are beneficial to improve material hardness and thus strength. These precipitates were dissolved in NZ and thermo-mechanically affected zone (TMAZ), and coarsen in heat affected zone (HAZ), which caused loss of hardness and strength. Similarly, precipitate morphology, size, and distribution are different in the built direction. Excellent tensile strength and elongation were identified in the NZ, which is attributed to fine grains and desirable precipitate characterization. • Defect-free build was fabricated using friction stir additive manufacturing. • Microstructure. evolution was clarified in detail by EBSD and TEM. • Local mechanical properties was evaluated using hardness mapping and DIC. [ABSTRACT FROM AUTHOR]