Al-12Si Alloy Research Articles

Processing defect, microstructure evolution and mechanical properties of laser powder bed fusion Al-12Si alloys

The laser power and scan speed are significant processing parameters influencing the defects and microstructures due to affecting the thermal state within the melt pool during laser powder bed fusion (LPBF). To this end, these process parameter combinations under a constant laser energy density are correlated with defects (balling phenomenon and pores) and microstructures (melt pool arrangement and cell morphology). Setting the parameter combination (laser power and scan speed are 200 W and 910 mm/s, respectively) yields large balling droplets (average size of 150 μm) due to the relatively high melt viscosity resulting from the low melt pool temperature. In this case, a limited surface tension difference acting on a liquid surface cannot provide sufficient driving forces against viscous drags to promote the efficient spreading of the molten alloy. Cavity regions are formed between the large balling droplets and the previous layer, forming lack-of -fusion pores. By increasing the laser power and scan speed gradually, samples with relative densities greater than 99.5% are produced. This phenomenon can be attributed to the increases in laser power and scan speed, which improves the spreading ability of the molten alloy. With increasing laser power and scan speed, the cell size decreases (from 0.51 μm to 0.42 μm) because of the increase in the cooling rate. The sample (laser power and scan speed are 350 W and 1590 mm/s, respectively) has the highest performance (310 MPa yield strength, 470 MPa ultimate tensile strength, and 6.6% fracture strain) due to its highest relative density (greater than 99.5%) and fine microstructure (average cell size of 0.45 μm). All four samples exhibit anisotropic mechanical properties resulting from the combination of the melt pool boundary and lack-of-fusion pores.

Effect of casting modifiers on surface roughness and chip formation of Al-12Si alloy

ABSTRACT In this study, the effects of casting modifiers on the surface roughness and chip formation of Al-12Si alloy materials were experimentally investigated. Machinability tests were carried out using a conventional lathe. Machinability tests were performed on four different materials, Etial 140, Etial 140 +CuSn5, Etial 140 +Al10Sr and Etial 140 +Al10Sr+CuSn5, respectively. A constant depth of cut, 3 different cutting speeds (Vc: 35, 95, 135 m/min) and three different feed rates (f: 0.08, 0.16, and 0.32 mm/rev) were chosen as test parameters. The most effective roughness reduction under these test conditions was 7.21% for the Al10Sr modified test material. According to the measured density values of the unmodified material, the density values of the other tested materials increased by 1.65% for CuSn5, 0.40% for Al10Sr and 1.16% for CuSn5+Al10Sr. Furthermore, the hardness values increased by 5.48% for CuSn5, 0.58% for Al10Sr, and 15.75% for CuSn5+Al10Sr.

Correction to: Al-12Si Alloy Fabricated Via Selective Laser Melting: Residual Stress and Microstructural Factors after Heat Treatment

Correction to: Al-12Si Alloy Fabricated Via Selective Laser Melting: Residual Stress and Microstructural Factors after Heat Treatment

Corrosion behavior of strontium modified Al-12Si cast alloys in flowing and stagnant chloride containing media

The Al-12Si alloy was modified with strontium varied from 0.1% to 0.35% in order to unveil its effect on corrosion resistance in static as well as in flowing solution with and without 3.5% NaCl at pH∼11. The Sr contents upto 0.18% changed the eutectic morphology to fine fibrous network beyond which, the acicular silicon begun to emerge. The corrosion resistance of both modified and unmodified Al-12Si alloy during flow reduced to as low as 30% of that observed during static condition. The 0.25% Sr containing alloy exhibited superior corrosion resistance to other variants including unmodified alloy. The Raman spectroscopy and XRD analyses of corrosion product unveiled the presence of bayerite on both unmodified and modified Al-12Si alloys, irrespective of presence of Cl- in the solution. The Sr additions, except 0.25%, degrades corrosion resistance of Al-12Si alloy in both during flow and static conditions. The corrosion resistance of 0.25% Sr is correlated to the evolution of thicker and different oxide morphology along with presence of relatively large silicon on the surface after corrosion.

Introducing Hatch Spacing into Deposited Energy Density toward Efficient Optimization of Laser Powder Bed Fusion Process Parameters

The optimization of processing parameters is indispensable for the laser powder bed fusion (L-PBF) process. The deposited energy density (DED) is one of the process indexes for the L-PBF process and has a simplified formula of P·v−0.5, where P is the laser power, and v is the scan speed. This parameter describes the change in the relative density and the melt pool morphology with laser power and scan speed well, whereas it does not include the effect of other processing parameters, e.g., hatch spacing (S). In the present study, an attempt was made to incorporate the effect of S into DED. Al–12Si (mass%) alloy cube samples were fabricated by L-PBF under various P, v, and S, for evaluating the relative density and the melt pool morphology. The melt pool depth and width of L-PBF-manufactured Al–12Si alloy increased linearly with P·v−0.5 and did not exhibit a clear correlation with S. Based on the experimental observation, the effect of hatch spacing on DED was estimated to be S−0.5, and a new index of P·v−0.5·S−0.5 was proposed. This index described the change in the relative density of the L-PBF-manufactured Al–12Si alloy with laser conditions (P, v, and S) well when the thermal conduction mode melting was dominant. This study also indicated the limitation of the applicability of P·v−0.5·S−0.5 under the keyhole or transition mode melting.

Effects of Mg content on microstructure, mechanical properties and fracture behavior of wrought Al–8Si–(

In this paper, the effects of the Mg content on the microstructure, mechanical properties and fracture behavior of wrought Al–8Si–(<0.01–1.32)Mg (mass fraction, %) alloy sheets in T6 temper were systematically studied by OM, SEM/EDS, EBSD, LSCM, DSC, TEM and tensile tests. The results show that the size of Si particles decreased slightly with the increase of Mg content, and the recrystallized grain size of experimental alloy sheets was refined from about 16 µm to about 11 µm. The size of β" phases did not change obviously, but its volume fraction increased gradually and then became stable. When Mg content was 1.32%, there were many associated aggregation areas of Mg2Si particles and Si particles in alloy sheet. In addition, the strength of experimental alloy sheets showed an initial increase followed by a slight decrease as the Mg content increased, while the elongation gradually decreased. The finite element model accurately predicted the yield strength of Al–8Si–(<0.01–1.32)Mg alloy sheets in T6 temper, and the model was able to quantify the contribution of various strengthening mechanisms to the yield strength of the alloy sheets. The predicted results were in good agreement with the actual measured results. The tensile fracture mode of Al–8Si alloy sheet was ductile fracture. When Mg content was greater than 0.51%, the fracture pattern of the sheets comprised a combination of ductile and brittle fractures. With the increase of Mg content, the number of dimples in experimental alloy sheets increased slightly, the depth gradually became shallow and the size slightly decreased. Meanwhile, most secondary cracks on the surface of the Al–8Si alloy sheets after tensile fracture bypassed the Si particles and a few sheared the Si particles. With the Mg content gradually increasing to 0.78%, the number of Si particles sheared by secondary cracks gradually increased. However, When Mg content was 1.32%, the intergranular fracture phenomenon of Al–8Si–1.32Mg in T6 temper was weakened or even disappeared. There were multiple particles embedded in the same dimples in the tensile fracture. The particles in the associated aggregation areas were more easily broken.

Effect of Cooling Conditions on the Solidification Microstructure and Mechanical Properties of Al–18Si Alloy

Effect of Cooling Conditions on the Solidification Microstructure and Mechanical Properties of Al–18Si Alloy

Laser additive manufacturing of strong and ductile Al-12Si alloy under static magnetic field

Rapid cooling and solidification during laser additive manufacturing (LAM) can produce ultra-fine microstructure with higher strength. However, the non-uniform cell/grain structure can easily result in early stress concentration and fracture during deformation, which remains a major challenge for the LAM field. Using Al-12Si as the model alloy, we employed the external static magnetic field (SMF) to modulate the laser powder bed fusion process (L-PBF), demonstrating a uniform microstructure with a refined cell structure. The mechanical properties show that the SMF can produce a combination of high tensile strength of 451.4 ± 0.5 MPa and large uniform elongation of 10.4% ± 0.79%, which are superior to those of previously-reported Al-Si alloys with post-treatment or element alloying. The mechanism analysis based on multi-scale simulation reveals the determining role of SMF in rapid solidification, and this method is applicable to the microstructure control of other metallic materials during LAM.

Effect of Structural Refinement and Modification on the Mechanical Properties of Al-7Si Alloy

Effect of Structural Refinement and Modification on the Mechanical Properties of Al-7Si Alloy

Effect of (Ti + V)B2 on the Grain Structure of Al–7Si Alloy

Effect of (Ti + V)B2 on the Grain Structure of Al–7Si Alloy

Tailoring the strength and corrosion resistance of Al-7Si: Eutectic Si modification by Sr and Sc

The effects of different content of Sr and Sc on the microstructure, mechanical properties and corrosion resistance of an Al-7Si alloy were investigated. The presence of Sc in the Sr-modified Al-Si alloy resulted in multiple types of eutectic Si morphologies. The modification of eutectic Si improved the yield strengthen and elongation of Al-7Si alloys, but lead to the increase of boundaries between α-Al and eutectic Si particles, which caused decrease of corrosion resistance and polarization resistance. The incomplete modification offered a possibility to satisfy the require that a compromise between mechanical properties and corrosion resistance. The relationship between the content of Sr and Sc and the morphologies of eutectic Si in the alloy was also summarized.

Investigation of the Influence of Ni and Cu Additions on the Wear Behavior of Spray Formed Al-15Si Alloy at Elevated Temperature

Investigation of the Influence of Ni and Cu Additions on the Wear Behavior of Spray Formed Al-15Si Alloy at Elevated Temperature

On the nano–treating effect of Al2O3 on the eutectic Si in Al–Si alloy

An Al-15 Al2O3 alloy was added into Al-12Si melt to investigate the nano-treating effect of Al2O3 nanoparticles on eutectic Si crystals. It was found that Al2O3 clusters may be partly swallowed by eutectic Si or distribute surrounding them. As a result, the flake-like eutectic Si in Al-12Si alloy can transform to granular or worm-like morphologies, attributing to the influence of Al2O3 nanoparticles on the growth behavior of eutectic Si crystals. The orientation relationship between Si and Al2O3 was identified, and the possible modifying mechanisms were discussed.

Effect of mold and core preheating temperature on corrosion resistance of casting Al-12Si alloy U-shaped cooling channel

Temperature has an important impact on the corrosion resistance of mold with cooling channels prepared by casting method. The effect of preheating temperature of the mold and the carbon fiber core on the roughness and corrosion resistance of U-shaped cooling channels made of Al-12Si alloy was examined in depth. The experimental results suggest that as the preheating temperature increased from 273 K to 573 K, the roughness of the inner wall of the cooling channel reduced from 96.6 µ m to 77.0 µm. When the preheating temperature continued to increase to 723 K, the roughness increased to 85.3 µm. The wetting between the Al melt and the carbon fiber will reduce micro bubbles and waves on the channel wall as the preheating temperature rises, thereby reducing the roughness. However, with the further increase of preheating temperature, it will increase the solidification time of the Al melt. At this time, the carbon fiber and Al melt will take more time to react, which increases the roughness of the channel wall to a certain extent. The results of exfoliation corrosion show that the larger roughness will aggravate exfoliation corrosion. The prolongation of high temperature reaction time between the carbon fiber and the Al melt will lead to the segregation of Si, which is easy to cause intergranular corrosion. Therefore, reasonable preheating temperature has an important impact on the roughness and corrosion resistance of U-shaped cooling channels.

Effect of mixing temperature on microstructure of an Al-Si alloy prepared by controlled diffusion solidification

The effects of mixing temperature, i.e., the temperatures of two precursor melts (pure Al and Al-12Si), on the temperature and solute fields of resultant mixture, the nucleation and growth, and the size and morphology of primary grains during controlled diffusion solidification (CDS) of Al-8Si alloy were investigated by using simulation and calculation. The results indicate that a lower mixing temperature is helpful for achieving more supercooled microscale Al-rich pockets in the mixture, and increasing the width and supercooling degree of supercooling zone in the Al-rich pockets, and thus, the nucleation rate. The nuclei grow up in nondendritic mode, resulting in spheroidal, at least, nondendritic grains. In a successful CDS, the superheat degrees of the two precursor melts should be limited within several degrees, and it is not necessary to extra stipulate the superheat degree of target alloy melt (Al-8Si) when the requirement about Gibbs energies of the three melts is matched. Subsequent observation on casting microstructures shows that the employed simulation and calculation processes are reasonable and the achieved results are reliable.

Effect of casting modification materials on cutting forces of an Al12Si alloy used in aircraft technology

Abstract In this study, the effect of modification Al-12Si (Etial 140) casting alloy with Al10Sr, CuSn5, and Al10Sr + CuSn5 master alloys has been investigated with respect to the cutting forces. In order to characterize the morphology of materials used in this study, metallography, hardness, density tests, and chemical analysis were performed. An optical microscope was used to examine the microstructure of the samples. Machinability tests were performed with the turning method by using a titanium diboride-coated cementite carbide cutting tool. All experiments were carried out under dry machining conditions with three different cutting speeds and feed rates with a constant cut depth. After the turning test, scanning electron microscope (SEM) images were used to examine the build-up edge (BUE) formation on the cutting tool. It was determined that the modification process has a positive effect on increasing the density and hardness. According to the results, it was observed that cutting (Fc), feed (Ff), and tangential (Fr) forces decreased for all material groups with increasing cutting speed V. Furthermore, Fc, Ff, and Fr forces increased for all material groups with increasing feed rate f. Finally, the highest cutting forces were observed on the Etial 140 c + Al10Sr master alloy.

Tuning the reactivity and energy release efficiency in aluminum alloy thermite by eutectic silicon

The unstable energy release efficiency hinders the application of Al/CuO metastable intermixed composites (MICs) in pyrotechnic applications to some extent. To overcome this issue, systematic experiments of Aluminum-Silicon (Al-Si) alloy-thermites with different Si content (12 wt% and 20 wt%) have been investigated in the context of regulating the energy release process. Optical diagnosis methods were applied synchronously to measure the flame propagation velocity and temperature field variation. Scanning electron microscopy and differential scanning calorimetry were used to observe the morphology and analyze the thermal process. Results indicated that the introduction of silicon significantly stabilized the combustion process of Al-Si/CuO due to the fewer gas-phase products and slower reaction rate of Si with CuO, while the flame temperature changed little. Excess silicon wafer blocks observed by SEM on Al-20Si led to an enhanced transport of oxygen and fuel. This explained the abnormal reactivity of hypereutectic alloy. The total heat releases of Al-20Si and Al-12Si were respectively enhanced by 110.2% and 93.1% in comparison with that of Al under DSC tests. Infrared temperature measurement of the Mg/Teflon/Viton (MTV) column revealed that Al-12Si and Al-20Si alloy thermites ignited MTV column 569.06 and 540.48 ms faster than Al/CuO, respectively, as the energy output mainly existed in the form of high-temperature residues. These improvements are attributed to the synergistic effect of the reactivity of silicon and aluminum, as well as the phase change during reaction which provides a controllable energy release process of alloy thermite and a better ignition performance. These findings are expected to facilitate the development of the nature of Al alloys and are especially promising for the thermite technology driven by reliable energy release rates.

Al-12Si Alloy Fabricated Via Selective Laser Melting: Residual Stress and Microstructural Factors after Heat Treatment

Al-12Si Alloy Fabricated Via Selective Laser Melting: Residual Stress and Microstructural Factors after Heat Treatment

Mechanism of AlP modifying the morphology of Si in Al-20Si alloys based on experimental studies and first-principles calculations

ABSTRACT The modifying influence of aluminium phosphide to the morphology of primary Si and eutectic Si was investigated in hypereutectic Al-20Si alloys via adding Al-Cu-P master alloy (0.5, 1, 20 wt.%). Microstructural results showed when Al-Cu-P addition from 0 to 0.5%, primary Si phase decreases and eutectic Si phase size remains invariable; when addition higher than 0.5%, primary Si phase keeps invariable, eutectic Si phase size increases. To prove the nucleation effect of AlP on Si phase, interfacial properties of Si/AlP interface were investigated using first-principles calculations. Results showed the AlP(100)/Si(100) interface energy is between −1.45 J/m2 and −1.38 J/m2 for Al-terminated and P-terminated AlP model, both is much smaller than liquid Si/crystalline Si interface (0.34 J/m2), consolidates that AlP particles possess strong nucleation potency for Si phases. Therefore, the modifying influence of AlP to the morphology Si phase is well clarified as a function of AlP content in Al-20Si alloys.

Effect of Standing Time after Mixing on the Mixture Microstructure of an Al-Si Alloy during Controlled Diffusion Solidification with Simultaneous Mixing

Taking pure Al (938.15 K) and Al-12Si (858.15 K) melts as two precursors and the Al-8Si alloy as the target alloy, the effect of the standing time after mixing on the microstructure of a mixture during controlled diffusion solidification with simultaneous mixing was investigated via a simulation and experiment. The simulation results indicate that the entrapped air will promptly form bubbles and cause the mixture to overflow within a short time of 1.2 s. An effective blending action still occurs during the initial stage (i.e., 0–0.5 s) of the standing process, resulting in the significant homogenization of the temperature field due to the thermal conductivity being much higher than the solute diffusivity. This is due to the large difference between the two thermophysical parameters, causing nuclei to rapidly form in the pure Al melt close to the interface of the pure Al/Al-12Si melts during mixing. Some of the nuclei will remelt, and others will only grow towards the pure Al melt side in a stable solid/liquid interface during standing, resulting in nondendritic Al grains and an increase in their size but a decrease in their number. These changing tendencies of grain morphology, size and number due to the standing time are consistent with those from the experiment, implying the employed simulation and calculation, as well as the achieved results, are reasonable and reliable.