The novel Al-4.5Mg-0.32Sc-0.66Zr alloy was successfully fabricated by selective laser melting. The minimum porosity of 0.5% was obtained for a laser power of 180 W, a scan speed of 220 mm s−1 and a ...hatch distance in the range of 0.13-0.15 mm. The microstructure of the as-fabricated alloy consists of aluminum solid solution grains with a typical bimodal size distribution at about 3-5 m and 1 m. Nanosized Al3(Sc, Zr) particles with a size of about 20-50 nm mainly formed on grain boundaries after one stage annealing at 360 °C/6 h. Homogenously distributed Al3(Sc, Zr) dispersoids 5-8 nm in diameter formed after two stage annealing 300 °C/3 h + 360 °C/4 h. As result the plasticity is 6% higher after two-stage annealing than after one-stage annealing. The yield strength and the ultimate tensile strength after both heat treatments are 424-438 MPa and 465-480 MPa, respectively. The optimum strength and plasticity combination was obtained after two-stage annealing in the samples fabricated in the XY direction: YS = 435 MPa, UTS = 478 MPa and El. = 16%.
The effect of 0.07% Sc on t he phase composition and properties of a novel wrought Al–3.7Cu–2.3Er–0.8Mg–0.7Mn–0.2Zr–0.1Ti–0.15Fe–0.15Si alloy with a decreased content of alloying elements was ...investigated. The ingot microstructure contains a solid solution of aluminum along with Al
3
Er, Al
25
Cu
4
Mn
2
Er , and Al
8
(Cu, Mn, Fe)
4
Er phases. During crystallization, scandium becomes distributed between the aluminum solid solution and Al
3
Er phase. Approximately 0.8% Sc is dissolved in the Al
3
Er phase. In the studied scandium-containing alloy, the softening rate during annealing of the rolled sheets is lower, which is caused by an inhibition of the polygonization process due to higher density of dispersoids formed during homogenizing annealing of the ingots. The alloy has a higher onset temperature of recrystallization, since after an hour-long annealing at 400°C, it still contained non-recrystallized grains, while scandium-free alloy was completely recrystallized. The hardness of the 0.07% Sc- containing alloy with a lower content of the basic alloying elements is higher by 9–14 HV.
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•The coefficient of thermal expansion of the AlSi11CuMn alloy manufactured by SLM is 19.1·10−6 °C−1.•The hardness of the as processed AlSi11CuMn alloy is 144HV.•The ultimate tensile ...strength of 354 MPa and elongation of 5.4% were obtained after heat treatment.
The microstructure and mechanical properties of the novel AlSi11CuMn alloy manufactured by selective laser melting were investigated in the as processed state and after heat treatment. A fine eutectic structure formed in the as processed alloy. A duplex size structure formed after solution treatment. The thermal expansion coefficient was 19.1·10−6 °C−1 in the 20–100 °C range which is typical for cast Al-Si alloys. Increasing annealing temperature from 190 to 275 °C leads to a sharp decrease in the alloy hardness from 136HV to 119HV after 2.5 h. The hardness was significantly reduced from 136HV to 79–82HV after solution treatment at 515 °C. The yield stress, ultimate tensile strength and elongation were 288 MPa, 354 MPa and 5.4%, respectively after solution treatment at 515 °C and aging at 180 °C for 8 h.
–The effect of impurities of iron and silicon on the phase composition and mechanical properties of the Al–6.3Cu–3.2Y wrought aluminum alloy is investigated in this work. According to the results of ...X-ray diffraction of the cast alloy, the presence of Al
8
Cu
4
Y, (Al,Cu)
11
Y, Al
2
Cu, and AlCu phases was confirmed, and the presence of peaks that likely correspond to the Al
11
Cu
2
Y
2
Si
2
phase was noted. Elongated needle-like inclusions of the Al
11
Cu
2
Y
2
Si
2
phase, which does not change its morphology in the course of homogenization, appear against the background of the fragmented compact eutectic. At the temperatures of annealing of the deformed sheets up to 300°C, the structure of alloy is represented by grains elongated along the rolling direction and has a slightly higher hardness than the same alloy without impurities. This is caused by the presence of larger amount of sufficiently dispersed intermetallic particles in the structure. When increasing the annealing temperature, the difference in hardness between the considered alloys decreases. Recrystallization occurs starting from 350°С, the hardness of the alloys levels out. After annealings at 100 and 150°C, the studied alloy demonstrates a good level of strength characteristics, the conditional yield stress is 284–325 MPa, the conditional ultimate strength is 304–369 MPa, which is 20–30 MPa higher than in the alloy without impurities. In general, the presence of permanent impurities of iron and silicon in aluminum does not have a negative effect on the mechanical properties of the studied alloy.
The effect of small additions of erbium and zirconium on the microstructure, phase composition, kinetics of hardening during aging and softening during annealing after rolling of the ...Al–5Si–1.3Cu–0.5Mg alloy has been studied in this work. Erbium and zirconium form a phase of crystallization origin with aluminum, silicon, copper, and magnesium, which does not dissolve and does not change its morphology in the process of homogenization before quenching. Erbium and zirconium increase the aging effect after quenching, especially at 210°C, increase the yield stress at elevated temperatures, reduce the tendency to soften during annealing after rolling, and reduce the recrystallized grain size due to dispersoids formed during homogenization. Quenching of deformed sheets with subsequent aging leads to the achievement of slightly lower yield strength than low temperature annealing after rolling. In this case, a significantly higher ultimate strength of 344–375 MPa and ductility of 11.0–14.7% are achieved. The alloy with small additions of zirconium and erbium has higher characteristics of both strength and plasticity.
The effect of zirconium and erbium additives on the structure and mechanical properties of the cast alloy Al–5Si–1.3Cu–0.5Mg after the quenching and aging of an ingot and of a deformed sheet has been ...studied. An increase in the zirconium and erbium content from 0.15 to 0.2 wt % each leads to a substantial modification effect comparable to that via modification with the master alloy AlTi
5
B
1
. The grain size decreases from 200 to 80 µm in this case, while it reaches 750 µm in the alloy free of additives. The studied alloys are of a much higher ultimate compression yield stress at both room temperature (290–295 MPa) and 200°C (230–235 MPa) due to the smaller grain size and higher number of phases of crystallization origin. In this case, the formation of the erbium-containing phase, which is insoluble in the process of homogenization before quenching, slightly decreases the copper content in the solid solution. An increase in the zirconium and erbium content elevates the recrystallization-onset temperature and, at the same time, has no significant effect on the properties of deformed alloys after their quenching and aging: the yield strength is 271–285 MPa, the ultimate strength is 337–378 MPa, and the relative elongation is 6.7–17.5%.
The microstructure and thermal and mechanical properties of (FeCoNiCuCr)
100−
x
-Nb
x
multiprincipal-element alloys have been investigated in the as-cast and heat-treated state. The alloys were ...smelted by arc-melting in argon atmosphere. As-cast samples were produced by copper mold casting. The structure was studied by scanning electron microscopy (SEM) and x-ray diffraction (XRD) analysis. The calculated phase diagrams of the Fe-Co-Ni-Cu-Cr-Nb system were used to predict the phase composition. The predicted thermodynamic temperatures and phase areas were compared with those obtained using differential scanning calorimetry (DSC) and the results of SEM observation, respectively. Addition of 10 at.% Nb caused phase separation of the alloy in the liquid state. Addition of Nb caused an increase in the yield strength by solid-solution hardening and by the formation of intermetallic compounds. Heat treatment also affected the mechanical properties of the studied alloys.
The possibility of determining the hot cracking index using the calculated value of the effective solidification range is investigated for multicomponent cast aluminium alloys based on the system ...Al-Si-Cu-Mg with Mn, Ni, Fe and Zn additives. The upper limit of the effective solidification range was calculated as the temperature of formation of 65 wt-% solid phase using Sheil model. The linear relationship of the hot cracking index and the effective solidification range in the industrial and experimental multicomponent alloys based on the Al-Si-Cu-Mg system is demonstrated.
•The yield compression stress of the Al-Si-Ni-Fe alloy at 200 °C is 355 MPa.•The hardness of the as processed Al-Si-Ni-Fe alloy is 186HV.•High strength is provided by the fine structure formed by the ...Si, Al5Fe(Ni,Cu) and Al3(Ni,Cu) phases.
The novel Al-Si-Ni-Fe alloy with high compression strength at elevated temperatures has been successfully produced by selective laser melting at an average volumetric energy density of about 100 J/mm3 and has a relative density of 99,86%. The hardness of as fabricated Al-Si-Ni-Fe alloy is 186HV and it decreases during heat treatment to 124HV due to stress relief and silicon particle growth. The yield compression stress is 355 MPa at 200 °C. This high strength is provided by the fine structure formed by the Si, Al5Fe(Ni,Cu) and Al3(Ni,Cu) phases. The good strength properties of the alloy at elevated temperatures make it a quite promising lightweight material for high temperature applications.
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•The optimal temperature range for hot deformation of 10CrMoWNb steel was established.•A constitutive Arrhenius-type model of 10CrMoWNb steel was obtained.•The Nb7B4C4 phase was ...identified as a reason of the hot fracture of the steel.
High-Cr ferritic–martensitic steels are important materials for use in nuclear reactors. This study describes a development activity for this category of steels involving the investigation of the hot deformation behaviour and microstructure evolution during hot deformation of 10CrMoWNb steel. Hot compression and tension tests were performed in the temperature range of 900–1350°C by using a Gleeble 3800 thermomechanical simulator. The results indicate that the flow stress and ultimate tensile strength increase with a decrease of the deformation temperature and an increase of the strain rate. Based on the experimental true strain-true stress data, the modified Arrhenius-type constitutive model was established for a form of 10CrMoWNb ferritic–martensitic steel. The hot plasticity properties of the 10CrMoWNb steel increase with temperature up to 1275°C due to dynamic recrystallisation processes in the austenite phase. The reduction of area decreases when the temperature is higher than 1300°C and is zero at 1350°C for all strain rates because of the liquid phase appearance in the structure of the steel.
