β-Al5FeSi Phase Research Articles

Effect of Rotating Magnetic Field on Microstructure in AlCuSi Alloys

The solidification of AlCuSi alloys with Mn and Fe was studied by rotating a magnetic field to understand the effect of melt flow. The specimens solidified with a forced convection, low cooling rate and low temperature gradient. Electromagnetic stirring generated by an electric coil around the specimens caused a transformation from equiaxed dendritic to rosette morphology, occasionally with spheroids and minor dendrites. The transformation was quantitatively observed with a specific surface Sv, that decreased for almost all alloys and marked the flow effect on α-Al. The computer coupling of phase diagrams and thermochemistry (CALPHAD) technique was applied for the calculation of phase diagrams and property diagrams. Forced convection decreased secondary dendrite arm spacing λ2 in almost all alloys, while it increased slightly in one studied alloy. The length of detrimental β-Al5FeSi phases decreased in the alloy, where β starts to precipitate in the presence of α-Al, while increasing in alloys where β starts as first and grows in the fully liquid melt. The average overall dimension of the Mn-rich phases increased in almost all alloys, and the number density decreased under flow. The modification of spacing for AlSi-eutectics and Al2Cu was analyzed. It was found that the occurrence of Al2Cu does not influence the fluid flow and vice versa.

Effect of arc re-melting on microstructure, mechanical and tribological properties of commercial 390A alloy

To investigate the effect of the arc re-melting on the microstructure, mechanical and tribological properties of the 390A alloy, its ingot produced by the conventional induction melting method was subjected to the arc re-melting process. The microstructure of the 390A alloy was examined by OM and SEM. Mechanical properties of the 390A alloy were determined by the Brinell method and tensile tests. Tribological properties were investigated with a ball-on-disc type tester. It was observed that the microstructure of both conventional induction melted and arc re-melted 390A alloys consisted of α(Al), eutectic Al–12Si, primary silicon particles, θ-CuAl2, β-Al5FeSi, δ-Al4FeSi2, and α-Al15(FeMnCu)3Si2 phases. Re-melting with the arc process caused grain refinement in these phases. In addition, after this process, the α(Al) phase and primary silicon particles were dispersed more uniformly, and sharp edges of primary silicon particles became round. The arc re-melting process resulted in an increase in the hardness of the 390A alloy produced by the conventional method from 102 HB to 118 HB and the tensile strength from 130 to 240 MPa. It also caused an increase in the wear resistance of the 390A alloy and a decrease in the friction coefficient.

Fe-bearing phase formation, microstructure evolution, and mechanical properties of Al-Mg-Si-Fe alloy fabricated by the twin-roll casting process

The composition and morphology of the Fe-bearing phase play a significant role in the mechanical properties of aluminum (Al) alloy sheets. In this work, we have studied the formation of Fe-bearing phases in an Al-0.53Mg-0.69Si-0.14Fe (wt%) alloy under the twin-roll casting (TRC) and the direct chill casting (DC) processes, respectively. We found that the π-AlFeMgSi phase was formed in the as-cast TRC sample, while the β-AlFeSi phase was formed in the as-cast DC sample. The differences in the formation of Fe-bearing phases are attributed to the promotion of the peritectic reaction to form the π-AlFeMgSi phase via the TRC process. Furthermore, after homogenization treatment at 550 °C and 2 h, the π-AlFeMgSi phase in the as-cast TRC sample completely decomposed into the fine β-AlFeSi phase, while it was insufficient to dissolve the β-AlFeSi phase in the as-cast DC sample. This is owing to the lower dissolution temperature of the π-AlFeMgSi phase compared to the β-AlFeSi phase. The decomposition of the π-AlFeMgSi phase expands the solid solubility and promotes the aging precipitation, resulting in higher yield strength of the TRC sample than that of the DC sample during the peak-aging treatment. Our work provides new insight into the development of high-performance AA6xxx series alloys based on the TRC process.

Effect of Heat Treatment on Microstructure and Mechanical Properties of AlSi10Mg Alloy Fabricated by Selective Laser Melting

The effects of the heat treatment process parameters on the microstructure and mechanical properties of a selective laser melted (SLMed) AlSi10Mg alloy were systematically investigated. The SLMed AlSi10Mg alloy was treated with T1 (180°C× 4h + air cooling) process, which had the microstructure of fine α-Al grains, fine Si phase, and nano-sized precipitations. The microhardness significantly increased to 150 HV, which is even higher than as-SLMed one (126 HV). The microhardness of SLMed AlSi10Mg alloy treated with T4 (540°C × 2h + water cooling) heat-treatment process significantly decreased to 62 HV due to the growth of α-Al grains, Si phase and the formation of β-AlFeSi phase. However, the microhardness and ultimate tensile strength of AlSi10Mg alloy treated with T6 (540°C × 2 h water cool + 180°C × 4 h air cool) process decreased to 91 HV, although the strengthening precipitation of Mg2Si phase formed. It indicates that the Mg2Si phase cannot compensate for the adverse effect of grain growth. It may provide the best potential heat treatment method for fabricating the high strength SLMed AlSi10Mg alloy.

Crystal chemistry and electronic structure of the β-AlFeSi phase from first-principles

β-AlFeSi has a layered structure composed of FeAlSi blocks and exhibits a rich variety of crystal chemistry. Plate-like/rod-like β-AlFeSi particles formed in Al-based alloys have nontrivial influences on the mechanical performance of the cast parts. Here, we investigate the stability, crystal chemistry and electronic structure of the β-phase using the first-principles density-functional theory (DFT) method. We reveal that Si prefers on the Al1 or Al6 sites, forming stable β-Al4.5SiIFe or β-Al4.5SiVIFe (the Roman numerals represent the Al sites in the Rømming’s labels). This differs from the existing model with a homogeneous Si/Al distribution. Moreover, the calculations also find that stacking of the FeAlSi blocks leads to structural transformations. Electronically β-Al4.5SiFe is anisotropic with a narrow pseudo-band-gap, indicating its unusual physical properties. The obtained information here sheds some light not only on the stability and crystal chemistry of the β-phase as a member of the large family of the Fe-containing intermetallic compounds in Al-based alloys, but also on its potential applications as low-dimensional functional materials.

The Effect of the β-Al5FeSi Phases on Microstructure, Mechanical and Fatigue Properties in A356.0 Cast Alloys with Higher Fe Content without Additional Alloying of Mn.

Secondary-cast aluminum alloys have increasing industrial applications. Their biggest deficiency is their impurity content, especially Fe, which has low solubility in Al and almost all the content creates intermetallic phases. This work examines the effect of higher Fe content on the microstructure and properties of A356.0 alloy. At the same time, no other possibility existed to affecting the brittleness of the formation of the β phases. The calculation of Fecrit, ratio of Mn/Fe, quantitative and computed tomography analysis of porosity and Fe plate-like phases, measurement of mechanical and fatigue properties, and fractography analysis were performed in this study. The results show that gravity die casting into a sand mold, and the non-usage of Mn addition or heat treatment, do not have a negative effect on increasing the size of the Fe-rich plate-like phases. The longest Fe-rich phases have limited the pore growth and ratios, but their higher thickness led to greater porosity formation. The mechanical and fatigue properties correlate with the Fecrit level and the highest were for the experimental alloy with 0.454 wt.% of Fe. The experimental results confirmed the fact that if the Fe plate-like phases have a length of up to 50 µm, the fatigue properties depend more on the size of porosity. If the length of the Fe needles is more than 50 µm, then the properties are mainly affected by the length of these Fe phases.

Microstructures and Properties of V-Modified A380 Aluminum Alloy Produced by High Pressure Rheo-Squeeze Casting with Compound Field Treatment

The melt of V-modified A380 alloy aluminum alloy was treated by compound field of ultrasonic vibration (UV) and electromagnetic stirring (ES) around liquidus temperatures. Then the high pressure rheo-squeeze casting (HPRSC) process was used to produce an ingot with the alloy melt obtained. The results indicate that the polygonal Si2V phase is precipitated after adding vanadium to the alloy. With the increasing of V content from 0 to 1.05%, the average length and volume fraction of β-Al5FeSi phase is decreased to 30 μm and 1.44%, respectively. The refinement effects of UV, ES, and UV-ES compound field on the microstructure of the gravity casting alloy are as follows: UV-ES > UV > ES. When the pressure is increased from 0 to 400 MPa, the size of primary α-Al is decreased gradually, the morphology of β-Al5FeSi phase is changed from an acicular to a fine fibrous-like one, and the polygonal Si2V phase is refined to fine particle with an average grain diameter of about 8 μm. The ultimate tensile strength (UTS), yield strength (YS), and elongation of the alloy without V are lower than that of the alloy with 0.7% V under the same pressure. When the pressure is 400 MPa, the UTS, YS, and elongation of T6 heat-treated HPRSC alloy with 0.7% V are 301 MPa, 182 MPa, and 3.3%, respectively. With the decrease in the length of β-Al5FeSi phase, the quality index of the HPRSC alloy is increased.

Formation of Die Soldering and the Influence of Alloying Elements on the Intermetallic Interface.

Die soldering of die castings is a serious problem in the aluminum casting industry. The precise mechanism, the influence of the alloy composition, and the options for prevention have not yet been fully elaborated. A well-established solution for alloys with low iron content is the addition of manganese. However, up to 0.8 wt.% is necessary, which increases the amount of brittle phases in the material and consequently reduces ductility. Immersion tests with 1.2343 tool steel and pure aluminum as well as a hypoeutectic AlSi-alloy with Mn, Mo, Co, and Cr additions were carried out to systematically investigate the formation of die soldering. Three different intermetallic layers and a scattered granular intermetallic phase formed at the interface between steel and Al-alloy after immersion into the melt for a duration of 6 min at 710 °C. The combined presence of the irregular, needle-shaped β-Al5FeSi phase and the surrounding alloy was responsible for the bond between the two components. Mn and Mo inhibited the formation of the β-phase, and instead promoted the αC-Al15(Fe,X)3Si2 phase. This led to an evenly running boundary to the AlSi-alloy and thus prevented bonding. Cr has proven to be the most efficient addition against die soldering, with 0.2 wt.% being sufficient. Contrary to the other elements investigated, Cr also reduced the thickness of the intermetallic interface.

Effect of adding rare-earth cerium on the microstructure and acid rain corrosion resistance of the ADC12 alloy

Abstract The effect of adding cerium on the microstructure and acid rain corrosion resistance of the AlSi11Cu3 alloy was investigated by means of optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The AlSi11Cu3 alloy was doped with varying stoichiometries of cerium to generate AlSi11Cu3-xCe, where x = 0, 0.5, 1.0, and 1.5 wt.%. The results show that the α-Al, eutectic Si, and β-Al5FeSi phases in the AlSi11Cu3-1.0Ce alloy are significantly refined. Electrochemical tests demonstrated an increase in the self-corrosion potential value of the AlSi11Cu3-1.0Ce alloy from –670 mV to –628 mV relative to the untreated alloy. In addition, the AlSi11Cu3-1.0Ce alloy has the lowest corrosion current density (8.4 μA × cm–2). Immersion corrosion testing on the AlSi11Cu3-1.0Ce alloy revealed a corrosion rate of 0.71 mg × cm–2 × d–1, constituting a 72% reduction in the corrosion rate compared to the untreated alloy. These results indicate that the AlSi11Cu3-1.0Ce alloy has a high resistance to acid rain corrosion, which is the result of a refinement of the cathode phases.

Hot Deformation Behavior of Al-20Si-5Fe-2Ni Alloy Obtained by Spray Forming

Abstract The hot deformation behavior of an aluminum alloy containing 20 % silicon, 5 % iron, and 2 % nickel produced by spray forming has been investigated through hot compression tests. Tests were carried out at 400°C, 450°C, and 500°C and 2 strain rates (0.25 and 1 s−1). It was found that, under the deformation conditions applied, stress–strain curves were characterized by a distinct stress peak or a multipeaks trend indicating the occurrence of dynamic recrystallization (DRX). Microstructural observations, together with X-ray diffraction (XRD) analysis, also indicated a change in the type of intermetallics during hot deformation, with a reduction of δ-Al4FeSi2 and a corresponding increase of the stable β-Al5FeSi phase.

Influence of the dendritic microstructure and β-Al5FeSi phase on the wear characteristics in a horizontally solidified Al-7Si-0.4Mg-1.2Fe alloy

In this work an Al-7Si-0.4Mg-1.2Fe alloy (wt.%) was subjected to a horizontal solidification experiment using a water-cooled solidification device equipped with thermocouples to obtain temperature vs. time data which in turn allowed solidification thermal parameters, such as growth and cooling rates (VL and TR, respectively), to be determined. In turn, tribological behavior of samples with different secondary dendritic spacing (λ2) and β-Al5FeSi platelets length (βFe) were assessed by means of dry sliding wear testing performed in a rotating fixed ball machine, with wear volume and rate (WV and WR, respectively) being the two main investigated wear parameters. Quantitative metallography by optical and scanning electron microscopy along with energy dispersive X-ray spectroscopy enabled both as-cast microstructures and worn craters to be characterized. More significant variations in wear resistance of the investigated alloy were found for ranges of λ2 and βFe that lie within 12−20 μm and 14–36 μm, respectively, with the coarsening of the microstructure constituted by Al-rich primary phase dendrites surrounded by α-Al + Si + θ-Mg2Si + β-Al5FeSi eutectic structures favoring reduced WV and WR values. For λ2 and βFe values higher than 24 and 48 μm, respectively, both WV and WR stabilize assuming constant values that depend on the sliding distance. In addition to power type equations relating λ2 and βFe to VL and TR, mathematical expressions for variations of WV and WR with λ2 and βFe are also proposed. Finally, a comparative analysis with the literature is presented.

Evaluation of Optimization Parameters of Semi-Solid Metal 6063 Aluminum Alloy from Friction Stir Welding Process Using Factorial Design Analysis

The semi-solid-metal 6063 aluminum alloy was developed for the automotive industry. The objective of this research was to optimize parameters in friction stir welding process that can provide the highest tensile strength. The ANOVA factorial design was used to analyze rotation speed, welding speed, and tool geometry at different factor levels of experimentation. The results showed that the optimized tensile strength was 120.7 MPa from the cylindrical tool, rotation speed was from 1300 to 2100 rpm, and welding speed less than 75 mm/min in the coefficient of determination R2 was 95.09%, as can be considered from the regression equation. The examination of the stir-zone and thermal mechanical affected zone using SEM and EDX showed that the new recrystallization of the microstructure causes fine grain in the stir-zone, coarse grain in advancing-side thermal mechanical affected zone, and equiaxed grain in the retracting-side thermal-mechanical affect zone. The intermetallic compounds of β-Al5FeSi phase transformation phase were formed to three types, i.e., β″-Al5Fe, Mg2Si, and Al8Fe2Si phase were observed. Moreover, in the stir-zone and thermal-mechanical-affected zone, defects were found such as flash defects, void or cavity defects, crack defects, lack of penetration defects, tunnel defects, kissing bond defects, and dendrite formation defects affecting weldability.

Microstructure refinement and corrosion resistance improvement mechanisms of a novel Al-Si-Fe-Mg-Cu-Zn alloy prepared by ultrasonic vibration-assisted rheological die-casting process

The Al-Si-Fe-Mg-Cu-Zn alloy was used to manufacture large, thin-walled parts for 5 G base stations by using the ultrasonic vibration-assisted air-cooled stirring rod rheological die-casting (ACSR + UV R-DC) process. Investigations were performed on the microstructure and corrosion resistance of the ACSR + UV R-DC alloy which was then compared with traditionally die-casting (T-DC) and ACSR R-DC alloys. The results reported that the ACSR + UV R-DC process not only refined the primary α-Al (α1-Al), the eutectic silicon, and the secondary α-Al (α2-Al), but also significantly improved the morphology and distribution of the β-Al5FeSi phase. Pitting corrosion of the alloy mainly originated from the interface between the β-Al5FeSi and the α2-Al. At the initial corrosion stage, the α1-Al and the interface between the α2-Al and the eutectic silicon were not corroded. As the corrosion time increased, the pitting corrosion continued to spread in the eutectic region and connected to form one large corrosion area. Moreover, the corrosion resistance of the ACSR + UV R-DC alloy was better than that of the T-DC and the ACSR R-DC alloys. This was due to the refinement of the eutectic silicon and iron-rich phases, and the reduction of the potential difference between the iron-rich β-phase and the aluminum matrix.

Formation of θ-Al13Fe4 and the multi-step phase transformations to α-Al8Fe2Si, β-Al5FeSi and δ-Al4FeSi2 in Al–20Si-0.7Fe alloy

Formation of Al13Fe4 and the phase transformations on these particles between numbers of different types of Fe-containing intermetallic compounds (FIMCs) were observed in Al–20Si-0.7Fe alloy when solidified at a slow cooling rate (0.01 K/s). The experimental results show that the Al13Fe4 phase (monoclinic) solidified initially and transformed into an intermediate α-Al8Fe2Si (hexagonal) and nano-scaled α-Al grains via a quasi-peritectic reaction. Subsequently, the intermediate α-Al8Fe2Si transformed into β-Al5FeSi (monoclinic). The transformed β-Al5FeSi phase contained many defects, and with heat treatment (530 °C for 30 min) transformed into δ-Al4FeSi2 (tetragonal). The variation in the composition and the lattice parameters of these FIMCs was examined with TEM which shows that the phase transformation among FIMCs starts from FIMCs with lower Si content and process to FIMCs with higher Si content. The interfaces between each of these phases were examined to determine the orientation relationships between various FIMCs. The phase transformation mechanism and the FIMCs transformation sequence have been proposed based on the experimental investigation.

Simulation of the Composition and Cooling Rate Effects on the Solidification Path of Casting Aluminum Alloys

Solidification simulations were carried out for casting aluminum alloy A356 using PanSolidification module of Pandat software which enables consideration of back diffusion in the solid during solidification. The casting microstructure features including the solidified phases, phase fractions, and secondary dendrite arm spacing (SDAS) were simulated. The simulated results explain the experimental observations reasonably well. High throughput calculation was performed to understand the effects of alloy composition and cooling rate on the formation of the intermetallic phases and SDAS in the casting microstructure. The role of Mn in eliminating the formation of detrimental β-AlFeSi phase was also simulated and discussed.

The Failure Degradation of Recycled Aluminium Alloys with High Content of β-Al<sub>5</sub>FeSi Intermetallic Phases

In this study, the effect of the β-Al5FeSi phases on fracture surfaces in secondary AlSi7Mg0.3 cast alloys with common and higher amount of iron was investigated. Iron addition caused the formation of different Fe-rich intermetallic phases in aluminium alloys. Components made of secondary aluminium alloys commonly have a higher amount of such phases. Sharp needles as β-Al5FeSi phase lead to initiate stress tension, thereby contributing to increased risk of micro-cracks formation on the fracture surfaces. To determine the effect of β-Al5FeSi to fracture surfaces of AlSi7Mg0.3 cast alloy, SEM microscopy with energy-dispersive X-ray spectroscopy (EDX) was used to study the amount of needles phases, their morphology and violation wave. It was found that increasing Fe content increased the size and the number of Al5FeSi phases. The fractographic analysis of fracture surfaces shows an increasing amount of cleavage fracture in materials with a higher amount of iron, too.

Effect of Mn/Fe ratio on the microstructure and properties of 6061 sheets obtained by twin-roll cast

The effect of the Mn/Fe mass ratio on the microstructure and mechanical properties of vertical twin-roll cast 6061 sheets were investigated. The microstructure and morphology of the iron-rich phase of cast and rolled sheets were investigated using optical microscope, scanning electron microscopy, energy dispersive x-ray spectroscopy and transmission electron microscope. The effect of Mn on the equilibrium phase of 6061 aluminum alloy was analyzed by CALPHAD thermodynamic simulation. In addition, the mechanical properties of 6061 twin-roll cast sheets were tested using tensile tests. The results showed that as the Mn/Fe mass ratio increased, the iron-rich phase at the edge of 6061 twin-roll cast plates gradually transformed from acicular β-Al5FeSi phase to granular α-Al12(FeMn)3Si phase. The core gradually aggregated from a needle-like β-Al5FeSi phase to a star-like Al6(FeMn) phase, and finally to an irregular network and petal-like α-Al15(FeMn)3Si2 phase. When the mass ratio of Mn/Fe was 2.0, the twin-roll cast plates exhibited the best mechanical properties, with a tensile strength, yield strength and elongation of 204.80 MPa, 180.59 MPa and 17.83%, respectively.

Microstructure and corrosion behavior of as-cast ADC12 alloy with rare earth Yb addition and hot extrusion

The effects of rare earth ytterbium (Yb) addition and hot extrusion on the microstructure and corrosion behavior of as-cast ADC12 were studied by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experimental results demonstrate that both the Si phase and β-Al5FeSi phase in the alloy with 0.9 wt% Yb have been remarkably refined, and the Al3Yb intermetallic compound has also been obtained. The Si, β-Al5FeSi, and rare earth phases are further refined in the alloy at 0.9 wt% Yb and hot extrusion. The results of the immersion corrosion tests and electrochemical experiments show that the corrosion current density (8.56 µA/cm2) of the alloy with 0.9 wt% Yb addition and hot extrusion is 50.6% lower than the untreated alloy (17.33 µA/cm2), and the polarization resistance (9252 Ω·cm2) was 71.3% higher than the untreated alloy (2654 Ω·cm2). The corrosion in the cathode phase in the micro-battery was refined to varying degrees attributable to the addition of Yb and hot extrusion, where the cathode reaction in the corrosion process caused a decrease of the corrosion rate.

Machine tool vibration on dimensional accuracy and surface roughness during milling operation of Al6082 with indexable carbide inserts

In this research paper, machining tool vibration occurs because of relative motion between the work piece and the cutting tool, which influences the surface finish of the machined part and the lifespan of the cutting tool. Some of the parameters that influence machining tool vibration include feed rate, depth of cut and spindle speed. In this study, experimentation is carried out on a conventional vertical milling machine to investigate the influence of machining tool vibration on surface roughness during face milling operation of Al6082 alloy with indexable carbide inserts. The eutectic phase for joint of Al6082 is β-Al5FeSi eutectic phase. The machining is done in dry condition under the different combinations of Machining parameters designed through Taguchi L9 orthogonal array. The machining tool vibrations are captured with the help of tri-axial accelerometer. Analysis of variance (ANOVA) technique used to formulate the experimental data to analyze the effect of each parameter and machining tool vibration on surface roughness.

Influence of secondary phases of AlSi9Cu3 alloy on the plasma electrolytic oxidation coating formation process

To understand the formation and growth of plasma electrolytic oxidation (PEO) coatings in presence of different secondary phases in a substrate, PEO treatment was carried out on AlSi9Cu3 alloy at different treatment times ranging from 15 s to 480 s. The coating formation and evolution process was traced by surface and cross-sectional observation of the layers on the different phases of the alloy. The results demonstrated a sequential involvement of the different phases in the plasma discharges: firstly, discharges start on the α-Al matrix, then on the intermetallic Al2Cu and β-Al5FeSi phases at the same time and finally on the eutectic Si. The presence of intermetallic Al2Cu remarkably affects the initial dissolution, the deposition of conversion products and the ignition of discharges at the early stages of processing. Eutectic Si in the substrate exhibits the highest electrochemical stability at all stages and contributes in the beginning to a distinct coating morphology eventually. The resultant PEO coating tends to be uniform if processing times are longer and a double-layer structure appears in the coating.