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The solid fraction at the beginning of the forging process is an important factor affecting the performance of the casting-forging integrated forming, which is an innovative and efficient process. The solid fraction depends on the delayed forging time during the casting-forging integrated forming. This paper investigates the effect of delayed forging time on the microstructure of aluminum alloy forged during solidification using an innovative physical simulation method. In this work, a solidification-forging device compatible with the Gleeble system has been developed. Then, experiments were conducted at various delayed forging time. Temperature and force data were collected using the Gleeble system for analysis. Microstructural evolution was investigated using methods including Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Electron Backscattered Diffraction (EBSD), and Three Dimensional Computed Tomography (3D-CT). The results demonstrate that with the extension of the delayed forging time, the grain size of the alloy decreases gradually, and the coarse dendrite structure changes to the rose-shaped grains, and the local misorientation in the grain increases. Moreover, the effect of forging under different forging time on the casting defects of the alloy is studied. When the forging delay is extended to 8 s, the forging promotes the porosity caused by the liquid phase convection. However, with further extension of forging delay, the reduction of the liquid phase and the fracture of dendrites lead to the complexity of liquid phase channels, resulting in the increase of porosity. Additionally, forging near solidification can close shrinkage porosity.

Upon 98% reduction cold-rolling, a single layer AA3003 foil material of 115 μm thick was intermediately annealed at 300–420 °C/1-8 h, and the preferred temperature and time of the intermediate annealing for the laminated AA4343/AA3003/AA4343 composite foil material were determined. All of these samples were cold rolled by 40% to 70 μm thick and finally annealed at a temperature in the range of 300–550 °C for 1–9 h. Their sagging resistance and microstructure were investigated using simulated brazing treatment, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For the single layer AA3003 foil, the sagging distance decreased first and then increased with increasing intermediate annealing temperature, and the lowest sagging distance corresponds to the coarsest grain in the recrystallized sample. After the final annealing for the single layer, the sagging distance decreased monotonously. For the laminated foil subjected to the final annealing, the sagging distance curves decreased first and then increased with increasing annealing temperature and time. The improvement of sagging resistance was attributed to the recovery of two types of materials during annealing process. The deterioration of the sagging resistance in the laminated foils was due to the corrosion in the brazing process, resulted from the Si diffusion from the cladding layer into the core layer. It is the coarse grains, few dislocations and minimal diffusion of Si that are crucial for improving the sagging resistance of the laminated foils.

The influence of aging treatments on the dynamic mechanical response of the 7B52 laminated alloy, and the correlation between the SHPB impact performance of 7xxx laminated aluminum alloy and its base alloys were investigated. Through adjustments the aging temperature and duration, alloys were obtained under underaged, peak-aged, and overaged conditions. Subsequently, Split Hopkinson Pressure Bar (SHPB) impact tests were conducted. The results indicate that the SHPB impact strength of the base alloy is higher in the peak-aged state compared to the under-aged and over-aged states. Additionally, as the aging temperature decreases, the alloy's impact toughness increases. The impact strength of laminated plates can be assessed by computing a linear weighted sum of the impact strength of individual alloys. The impact toughness of laminated aluminum alloys is notably influenced by the disparity in impact strength between 7A52 and 7A62 alloys. When the difference in impact strength between base alloys is small, the deformation of laminated plates is uniform, which can enhance the additional impact toughness of laminated aluminum alloys. Finally, an impact performance prediction formula for laminated plates is provided through linear fitting.

This work discusses the characterization of the hot cracking resistance and mechanical properties of Al-Cu-Mn-Cd (-Er-Zr) alloy using the “constrained rod casting” method and mechanical tensile testing. Analysis of the Al-Cu-Mn-Cd (-Er-Zr) alloy's microstructure was conducted using testing methods such as optical microscopy, scanning electron microscopy, transmission electron microscopy, and others. The results indicate that alloys with the addition of Er and Zr exhibit higher resistance to hot cracking compared to alloys without Er and Zr. The Er and Zr mainly refine the grain size by increasing the degree of ingredient supercooling, while simultaneously improving the alloy’s resistance to hot cracking by increasing the proportion of eutectic structure. The addition of Er and Zr results in grain size refinement and a reduction in the secondary dendrite arm spacing. The average grain sizes of alloys containing Er and Zr, and alloys without Er and Zr, are 138.43 μm and 151 μm, respectively. The average spacing of secondary dendrite arms is 21 μm and 31 μm, respectively. The average tensile strengths of alloys treated with T6 heat treatment are 500 MPa and 474 MPa, respectively. During the heat treatment process of the alloy containing Er and Zr, the formation of the Al3(Er, Zr) phase provides non-uniform nucleation sites for the θ′ phase, thereby reducing the size of the θ′ phase and consequently enhancing the strength of the alloy.

The effects of Si addition to Fe on the formation and growth of intermetallic compounds (IMC) in Fe/Al composites were studied by Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and electron backscatter diffraction (EBSD) techniques. The results showed that: when annealing time was 1 h, the critical IMC formation temperature of Pure Al/Pure Fe, Pure Al/Fe+0.82Si, Al+0.88Si/Pure Fe and Al+0.88Si/Fe+0.82Si were 440 °C, 480 °C, 520 °C and 620 °C, respectively. The major IMC phase formed in the four composites after heat treatments at 640 °C/1h and 640 °C/24h was the η phase (Fe2Al5), and a large number of θ phase (Fe4Al13) particles were present in the η phase for the Pure Al/Pure Fe sample. When Si element was added to Fe and Al, Fe3Al2Si3phase and FeAl2Si phase were observed in the η phase. The thickness of the formed IMC layer in the four composites after heat treatment at 640 °C/1h was in the order: Pure Al/Pure Fe ≈ Pure Al/Fe+0.88Si > Al+0.888Si/Pure Fe ≈ Al+0.888Si/Fe+0.88Si. The growth activation energies of the IMC layer in the Pure Al/Pure Fe, Pure Al/Fe+0.82Si, Al+0.88Si/Pure Fe, Al+0.88Si/Fe+0.82Si samples were 76.1 kJ/mol, 276 kJ/mol, 349 kJ/mol and 519.6 kJ/mol, respectively. The effect of Si atoms on the formation of IMC was mainly by the interfacial enrichment mechanism and the new phase inhibition mechanism of FexAlySiz. The enrichment of Si at the interface of Al and Fe increased the growth activation energy and reduce the growth rate of IMC layer thickness. The formation of new FexAlySiz phase can inhibit the rapid growth of IMC phase along the C axis.

This work aims to study the influence of laser power on the microstructural evolution of novel Ti–6Zr–5Fe alloy fabricated by selective laser melting (SLM). The microstructural evolutions of all top surfaces in SLM Ti–6Zr–5Fe alloy samples fabricated from 80 W to 140 W were investigated in depth. The microstructure in SLM Ti–6Zr–5Fe alloy includes α phase and β phase, the size of the β phase and α phase increases with the increase of laser power due to the decrease of cooling rate. Meanwhile, the melt pool overlapping width increases with the increase of melt pool width due to the increase of laser power. The increase of melt pool overlapping causes the re-heating or re-melting of SLM Ti–6Zr–5Fe alloy. Moreover, as the laser power increases from 80 W to 140 W, the change of the melt pool greatly influenced the size, morphology, crystallographic orientation of the β phase, and their distributions. The increase of laser power causes adequate precipitation of the α phase, which improves the microhardness from 466 HV to 533 HV. The laser power can effectively regulate and control the microstructure and microhardness of SLM Ti alloys.

In order to improve the mechanical properties of Al–Si alloys fabricated by selective laser melting process, the microstructure and mechanical properties of Er/Zr modified A357 (Al–7Si-0.6 Mg) alloy in as-built and stress relief annealing conditions were studied. The results show that adding 0.15 wt.% Er helps to refine the cellular size, which is formed by eutectic Si network. The (Al,Si)3(Er,Zr) phases were precipitated during the solidification of Er–Zr composite modified sample, which could act as inoculants to promote the formation of equiaxed grains and refine the grain size. The average grain size of 0.8Er-0.4Zr sample was only 3.1 ± 1.4 μm. The yield strength, tensile strength and elongation reached 333 ± 2 MPa, 454 ± 1 MPa and 12.5 ± 1%, respectively. After stress relief annealing, eutectic Si was spheroidized and its size was increased, resulting in a decrease of strength and an increase of elongation. At the same time, the nano-sized L12-structure particles were precipitated in the Er–Zr composite modified sample, which would make up for the loss of strength and level it up to a certain extent. Therefore, Er–Zr composite modification could be an effective method to improve the comprehensive mechanical properties of SLM processed Al–Si alloys.

Microstructural evolution and its effect on microhardness and Young's modulus of Ti–6Zr–4Fe alloy solution and aging treated at different temperatures were studied. The α phase transformed into β phase completely at 860 °C, meanwhile, the athermal ω phase was found at 860 °C and it resulted in a higher Young's modulus. The ω phase content increased from 250 °C to 400 °C, and the content decreased with further increase of aging temperature, there were only α phase and β phase at 600 °C. The phase transformation sequence was β → ω + β → ω + α + β → α + β during aging treatment. The microhardness increased from 315 HV to 492 HV due to the element solution strengthening and phase transformation strengthening. The peak microhardness of Ti–6Zr–4Fe alloy aged at 400 °C reached 652 HV. The formation of ω phase resulted in the increase of microhardness and Young's modulus in Ti–6Zr–4Fe alloy.

With the rapid development of the machinery industry, bearing materials with better tribological properties are demanded. Al alloys containing Erbium (Er) and Zirconium (Zr) have better comprehensive performance, whose tribological properties have hardly been reported before. In this work, dry sliding wear tests were performed on the Al–Sn and Al–Sn–Er–Zr alloys in two different annealing states to study the effect of trace Er, Zr on the tribological properties of the Al–Sn alloys. The Al–Sn–Er–Zr alloys showed better wear resistance than the Al–Sn alloys, which was mainly due to the higher hardness and strength of the Al–Sn–Er–Zr alloys. The wear losses of the alloys annealed at 375 °C for 100 h at the load of 70 N were significantly lower than those of the alloys annealed at 300 °C for 4 h. The wear coefficient Kof the alloys annealed at 375 °C for 100 h decreased with the increasing load. The Al–Sn–Er–Zr alloys showed smoother worn surfaces than the Al–Sn alloys. With the load increasing, the wear mechanism changed from abrasive wear, mild adhesive wear and slight delamination wear to severe adhesive wear and delamination wear. The wear scars of different samples under the same load were similar, indicating that the addition of trace Er, Zr and annealing process did not change the wear mechanism. All samples experienced cracks and voids in the tribolayers. And oxygen accumulated in these defects. Most wear debris were lamellar, which was related to the adhesive wear and consist with the delamination theory.

Aging behavior and phase transformation of Al–5Zn–1Mg–1Cu(-Si) alloys under different isothermal temperatures were investigated using transmission electron microscope (TEM) and mechanical tests. The aging temperature and Si addition significantly influenced to the types of precipitated phases and mechanical properties of the Al-Zn-Mg-Cu alloys. Adding Si in this alloy changed the precipitated phases from T' and η' phases to the dual-sized η and GPB-II phases. With increasing isothermal aging temperature, more GPB-II phases formed in alloys with the same composition, effectively improving the microhardness and mechanical properties. When aging at 150°C, 0.5wt%Si-containing alloy reached the highest peak hardness of about 150HV and maintained stable hardness, while an alloy without Si only reached 120HV and later declined by 15HV. The tensile strength and yield strength of the 0.5wt%Si-containing alloy were higher than those of non-Si alloy by 132 MPa and 165 MPa, increasing 51% and 90%, respectively. This result was due to the presence of fine and dispersed 4-8 nm GPB-II phases in 0.5wt%Si-containing alloy. The GPB-II phase had a core-shell structure, with the core region mainly enriched in Mg and Si, and the shell region mainly enriched in Cu and Zn. Compared with the stability of T' and η' phases, this core-shell structure of GPB-II effectively inhibited its growth and beneficially maintained a smaller-sized GPB-II phase. The strengthening effect of GPB-II phase was better than that of η or T phases when aging at 150°C or 200°C. The mechanical properties of high Zn/Mg ratios Al-Zn-Mg-Cu alloys can enhanced by adding Si.

The depth profiling of the element content and precipitation phase distribution of the AA4045/AA3003mod (Al-1.5Mn-0.35Cu alloy)/AA4045 brazed sheets were investigated by optical microscope observation, electron probe microanalysis (EPMA), focused ion beam-scanning transmission electron microscopy (FIB-STEM). The electrochemical test and sea water acetic acid test (SWAAT) were performed to obtain the evolution of electrochemical responses and corrosion forms of brazed sheet. EPMA results showed that a diffusion layer with the thickness of approximately 50μm existed between the clad layer and core layer, where the Cu diffused from the core layer and Si diffused from the clad layer. It was found that brazing led to a significant low elements solid solution area at the end of the Si diffusion path, where the open circuit potential was lower by 25mV comparing to the unaffected region. Thus the diffusion zone can provide effective cathodic protection to the unaffected region as sacrificial anode by the potential gradient. The SWAAT analysis revealed the corrosion mechanism of the residual cladding was pitting and intergranular corrosion. This area with high density of intermetallic compounds and Si particles increased sensitivity to localized attacks. These results demonstrated the successful application of the FIB-STEM system in illustrating the electrochemical responses and corrosion propagation by an accurate in-depth characterization of intermetallic particles and the matrix solid solution.

Al–Sn–Si alloys have been widely used as bearing alloys in automotive engines. In those alloys, β(Sn) phase serves as the solid lubricant and Si particles are used to improve the hardness, fatigue resistance as well as seizure resistance. With the development of machinery, bearing alloys with higher load-carrying capacity and better tribological properties are demanded to meet the application under severe conditions. Adding appropriate Mg to the Al–Sn–Si alloy can effectively optimize the tribological properties. In this paper, the microstructure, mechanical properties and tribological properties of the Al–12Sn–4Si-xMg (x = 0, 0.5, 1, 1.5, all in wt.%) alloys were studied. The Al–12Sn–4Si-1.5 Mg alloy had the smallest grain size and more uniform microstructure than other specimens. The Al–12Sn–4Si-1.5 Mg alloy showed significantly better wear resistance than the Al–12Sn–4Si alloy at 2 N–70 N. The volume wear rates and friction coefficients at 15 N–70 N were lower than those at 2 N–8 N. The evolution of volume wear rate and friction coefficient with load was related to the evolution of tribolayer with load. The wear mechanism of the alloys was mainly oxidation wear, adhesive wear and fatigue wear, accompanied with abrasive wear.

Isothermal hot compression experiments of homogenized Al–Mg–Si–Er–Zr alloy were conducted at temperatures ranging from 350 to 500 °C and strain rates of 0.01–10 s−1on a Gleeble-3500 thermal simulation tester. The hot deformation behavior and optimum processing parameters of the alloy were determined by analyzing the flow curves and processing maps. Characterization of the microstructures of the deformed specimens was done using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), and the geometrically necessary dislocation (GND) density was used based on the kernel average misorientation (KAM). The results showed that the GND density decreased with a decrease in the strain rate and with an increase in the deformation temperature. Dynamic recovery and continuous dynamic recrystallization were the main softening mechanisms during hot deformation, and dynamic recovery was dominant. It was found that the capacity for dynamic recovery was reduced, while dynamic recrystallization was prevented in the Al–Mg–Si–Er–Zr alloy. This was a result of hindered dislocations and sub-grain boundary movement caused by the pinning of dislocations and sub-grain boundaries from the Mg2Si, Al(MnFe)Si, and Al3(Er, Zr) particles. The addition of Er and Zr resulted in an increase in the activation energy, which can be attributed to the formation of Al3(Er, Zr) particles.

The Al–7Si–0.6 Mg alloy with added rare earth erbium (Er) was prepared by laser powder bed fusion (LPBF) technology, and the effect of heat treatment on the microstructure and mechanical properties was studied. The addition of Er introduces Al3Er to the molten pool, which can effectively hinder the epitaxial growth of the columnar crystal. The effect of rapid cooling and the addition of Er can also modify eutectic Si particles, resulting in an ultrafine eutectic network cellular structure. Moreover, the as-built samples have an excellent tensile strength exceeding 438 MPa and a ductility of over 8%; furthermore, such excellent mechanical properties are associated with small grains, a continuous Si network, and extremely oversaturated solid solubility. After heat treatment, LPBF-processed alloy samples exhibit superior mechanical properties, especially after direct age treatment, which can mainly be attributed to the precipitation strengthening effect introduced by nanosized precipitates.