Nikolay V. Letyagin

The limited thermal stability of conventional aluminium alloys at elevated temperatures restricts their application in laser powder bed fusion (LPBF). In this study, a novel Al₆Ca₃Cu_1.8Mn_0.4Zr (wt.%) alloy was developed for improved thermal stability via stable intermetallic phases. LPBF processing of gas-atomised powder identified a reference processing window at 350 W and a hatch distance of 0.08 mm (~97–122 J·mm⁻³), enabling fabrication of crack-free samples with relative densities above 99.0%. The as-built microstructure consists of a highly refined cellular structure with a quasi-continuous network of intermetallic phases and nanoscale dispersoids within the α-Al matrix, resulting in a yield strength of 206 ± 15 MPa, an ultimate tensile strength of 312 ± 2 MPa and an elongation of 2.7 ± 0.2%. Annealing (350 °C/3 h) leads to partial fragmentation and spheroidization of intermetallic phases, accompanied by a slight decrease in strength (UTS = 277 ± 10 MPa) and elongation (2.4 ± 0.3%), while fracture remains predominantly ductile. The alloy shows softening resistance: room-temperature hardness remains close to the as-built value after annealing at 250–300 °C, whereas more pronounced softening is observed after annealing at 350–400 °C, with subsequent stabilization during prolonged holding.

A novel heat-treatable wrought alloy (wt. %): Al–5.6Cu–0.35Ca–0.51Mn–0.29Zr was cast as a 20 mm thick flat ingot, followed by homogenization annealing and hot rolling at 450 °C to a final thickness of 2 mm. Scanning electron microscopy (SEM) confirmed that the copper solubility in the aluminum matrix reached ~5.1 wt. %, satisfying the requirements for a pronounced precipitation hardening effect. Aging at 175 °C revealed a peak hardness of 145–150 HV achieved within ~4 h, which is comparable to the commercial 2219 alloy. Transmission electron microscopy (TEM) data suggest that the hardening is due to the formation of ultrafine coherent θʹʹ phase precipitates. Intergranular corrosion (IGC) tests showed that the new alloy performs similarly to the commercial AK4–1 alloy, with a mass loss of ~2 % after 24 h and a corrosion depth of 150–200 µm. Uniaxial tensile testing after corrosive exposure revealed a 20 % reduction in tensile strength for both alloys. Notably, the fracture mechanism in the corrosion-affected zones shifted from ductile transgranular dimpled fracture to brittle intergranular mode

Developing specialized aluminum alloys for additive processes is a strategic approach to achieve both strength and mass reduction in high-performance products. The prospects of the new metallic powder composition of Al3Ca2La2Mn0.4Zr alloy for laser powder bed fusion (LPBF) have been studied. It has been found that the best printing mode, providing a more than 99.0% density of the specimens, includes substrate heating to 150 °C and printing with a 350 W laser power, a 1500 mm/s printing speed, a 0.08 mm hatch distance and a 0.03 mm layer thickness (energy density 97.2 J/mm²). The optimal printing mode provides for the following strength parameters: UTS 366 ± 5 MPa, yield strength 223 ± 8 MPa, and relative elongation 30 ± 3%. The alloy exhibits high thermal stability for the structure and its properties. Annealing temperatures below 300 °C have no critical effect on the alloy hardness: the hardness decreases by less than 10% of the initial 110 ± 3 HV. At 350 °C, the hardness decreases by 25.5% (82 ± 2 HV); 100 h exposure at 350 °C reduces the UTS to 265 ± 2 MPa and the yield strength to 178 ± 10 MPa, while maintaining the relative elongation of 29 ± 2%.

Numerical simulation of metal forming processes is finding increasingly wide applications in advanced industry for the optimization of material processing conditions and prediction of process parameters, finally delivering a reduction of production costs. This work presents a comparison between simulation results of radial shear rolling (RSR) of VT3-1 titanium alloy (Ti-Al-Mo-Cr-Fe-Si) and results of experimental RSR at 1060 °C, 980 °C, and 900 °C in one, three, and five passes, respectively. The digital model (DM) demonstrates a high convergence of the calculation results (calculation error of less than 5%) with the actual geometric parameters of the experimental bars, their surface temperature, and rolling time during the experiment, which indicates a good potential for its application in the selection of deformation modes. Based on the simulation and experimental data, the conditions providing for the formation of differently sized grains in the bar cross-section have been identified. All of the as-rolled bars exhibit a gradient distribution of macrostructure grain size number (GSN), from the smallest one at the bar surface (2–4) to the greatest one in the center (4–6). The macrostructure GSN correlates with the workpiece temperature, which is the highest in the axial zone of the bars, and with the experimentally observed high plastic strain figures in the surface layers. It was found that, depending on the temperature conditions and reduction ratio per pass, any minor change in the values of process parameters can lead to the formation of macrostructures with different grain size numbers.

In this study, prospects of designing new Al–Ca–Cu–Mn (Zr) alloys for additive manufacturing (AM) were evaluated for the example of laser remelting of thin-sheet rolled products. The new as-cast alloys have a hypereutectic structure containing Al₂₇Ca₃Cu₇ primary crystals and ultrafine eutectic particles of (Al,Cu)₄Ca and Al₂₇Ca₃Cu₇ phases in equilibrium with the aluminum solid solution. The solid solutions are additionally strengthened by alloying with Mn and micro additions of Zr, which contribute to the formation of coarsening-resistant phases without compromising the manufacturability of the alloys. Laser remelting, which simulates AM-typical solidification conditions, promotes the formation of a pseudoeutectic cellular structure without the occurrence of undesirable primary Al₂₇Ca₃Cu₇. The size of the dendritic cells and eutectic particles is 10 times smaller (for solidification rates of ~200 K/s) than that of the as-cast state. This structure provides for a higher hardness of the laser-remelted alloy (96 HV) as compared to the as-cast alloy (85 HV). Data for the alloy after 350–400 °C long-term annealing for up to 100 h show that the hardness of the Al–Ca–Cu–Mn–Zr alloys declines relatively slowly by ~7.5% as compared to the Zr-free alloy, whose hardness decreases by ~22%. Thus, one can consider these alloys as a promising candidate for AM processes that require high thermal stability.