Selective Laser Melting AlSi10Mg Research Articles

Effect of Deep Cryogenic Aging Treatment on Microstructure and Mechanical Properties of Selective Laser-Melted AlSi10Mg Alloy

Deep cryogenic aging (DCA) is a newly developed heat treatment technique for additive-manufactured metallic materials to reduce residual stress and improve their mechanical properties. In this study, AlSi10Mg alloy samples fabricated by selective laser melting were deep-cryogenic-treated at −160 °C and subsequently aged at 160 °C. Phase and microstructural analyses were conducted using X-ray diffraction, optical microscopy, scanning electron microscopy, and transmission electron microscopy, while the mechanical properties were evaluated through microhardness and tensile testing at room temperature. The results indicated that the DCA treatment did not have an effect on the morphology of the melt pools. However, it facilitated the formation of atomic clusters and nanoscale Si and β′ phases, as well as accelerating the coarsening of grains and the ripening of the eutectic Si phase. After DCA treatment, the mass fraction of the Si phase experienced an increase from 4.4% to 7.2%. Concurrently, the volume fraction of the precipitated secondary phases elevated to 5.1%. The microhardness was enhanced to 147 HV, and the ultimate tensile strength and yield strength achieved 495 MPa and 345 MPa, respectively, with an elongation of 7.5%. In comparison to the as-built specimen, the microhardness, ultimate tensile strength, and yield strength increased by 11.4%, 3.1%, and 19.0%, respectively. The improvement in mechanical properties is primarily attributed to the Orowan strengthening mechanism induced by the secondary phases.

On the Guinier-Preston zones in selective laser melted AlSi10Mg alloy

The strength of selective laser melted (SLM) AlSi10Mg alloy is usually higher than that of cast or heat-treated counterparts. Here we report that Guinier-Preston (GP) zones, needle-like and spheroidal Si-enriched particles, were presented in the SLM AlSi10Mg alloy, which contributed to the high strength as well as the high-density dislocations. The GP zones in the matrix were 1−2 atom layers thick along (111) planes and sized ∼4−10 nm. Dislocations and lattice strain were found adjacent to the GP zones by geometric phase analysis. These GP zones could be further utilized to optimize the strength of SLM aluminum alloy.

Comparison of Various Intrinsic Defect Criteria to Plot Kitagawa-Takahashi Diagrams in Additively Manufactured AlSi10Mg.

Selective laser melting is a form of additive manufacturing in which a high-power density laser is used to melt and fuse metallic powders to form the final specimen. By performing fatigue and tensile tests under various loading conditions, the study sought to establish the impact of internal defects on the specimens' fatigue life. Scanning electron microscopy and finite element simulation were conducted to determine the defect characteristics and the stress intensity factor of the specimens. Four different methods were used to determine the intrinsic defect length of the specimen, using data such as grain size, yield strength, and hardness value, among others. Kitagawa-Takahashi and El-Haddad diagrams were developed using the results. A correction factor hypothesis was established based on the deviation of measured data. Using Paris law, fatigue life was determined and compared to the experimental results later. The study aims to select one or more approaches that resemble experimental values and comprehend how internal defects and loading situations affect fatigue life. This study's findings shed light on how internal defects affect the fatigue life of selective laser-melted AlSi10Mg specimens and can aid in improving the fatigue life prediction method of additively manufactured components, provided an appropriate intrinsic crack criterion is selected.

Micro-cutting mechanism of selective laser melting AlSi10Mg containing inside metal particles based on finite element analysis

Micro-cutting mechanism of selective laser melting AlSi10Mg containing inside metal particles based on finite element analysis

Achieving high strength in selective laser melting AlSi10Mg alloy by adding microsized pure Cu particles

In this work, a high-strength Al–Cu–Mg–Si alloy was prepared by a selective laser melting (SLM) process with blended powders consisting of AlSi10Mg and microsized pure Cu powders. The influence of Cu addition on the microstructure and mechanical properties of AlSi10Mg alloy has been systematically investigated. The Al–Cu–Mg–Si alloy has a hardness of 173 HV, an ultimate tensile strength of 732 MPa, and a yield strength of 389 MPa, reaching the level of high-strength aluminum alloys. Such increase in the strength and hardness can be attributed to the refinement of eutectic network, enhanced solid solution strengthening and elimination of fracture-prone heat affected zone (HAZ). In addition, the formation of the GP zone caused by adding Cu promotes the precipitation of Si particles within the eutectic network, and Si particles, as the non-shear deformed second-phase, can significantly increase the Orowan strengthening effect. After aging at 180 °C for 2 h, the hardness and yield strength of the alloy are increased to 183 HV and 522 MPa respectively. The presence of the θ′-Al2Cu phase and the high-density of Si particles after 2 h of peak aging further increases the strength and hardness of the alloy.

On the capability of grain refinement during selective laser melting of AlSi10Mg alloy

This work focuses on the origin and capability of grain refinement in the microstructure of selective laser-melted AlSi10Mg alloy. The grains in printed microstructure have been oriented in a random manner and there is no sign of preferred micro-texture. In the molten pool, columnar grains have been formed aligned with the building direction, and stretched toward the center of the molten pool. The fraction of refined equiaxed grains by the size of fewer than 10 μm is considerable (∼40%) which have been formed (i) during solidification owing to high solidification rate to thermal gradient ratio, or due to (ii) the occurrence of dynamic recrystallization during the manufacturing process after completion of the solidification. These refined equiaxed grains have been differentiated through plotting Grain Orientation Spread maps. The numerous thermal cycles experienced by each layer cause considerable tensile or compressive micro-plastic strains and give rise to dynamic recrystallization. The presence of incomplete grains can be clearly traced which are ready to be evolved into the recrystallized grains. This, besides the extensive substructure development and sub-grain formation, are main proof for governing of continuous mechanisms of recrystallization mechanisms. Finally, selective laser melting has been approached as a thermomechanical processing route, and the calculated micro-plastic strain has been compared with a critical strain of dynamic recrystallization obtained from the hot compression testing method.

Study on Small Fatigue Crack Growth Rate of SLM AlSi10Mg Alloy

In this paper, the fatigue small crack growth rate of selective laser melting (SLM) AlSi10Mg alloy is studied by in-situ SEM experiment. The experimental results show that the small crack growth rate of SLM AlSi10Mg alloy can be described by Paris law, and the crack growth rate increases significantly with the increase in temperature. In addition, the combination of finite element simulation and fracture analysis shows that the pore is one of the main factors affecting the dispersion of small crack growth rate.

Effects of direct aging treatment on microstructure, mechanical properties and residual stress of selective laser melted AlSi10Mg alloy

• The as-fabricated microstructure benefits short-circuit diffusion of Si. • Direct aging treatment promotes unique precipitation behaviors. • Direct aging removes roughly 40% of the residual stress. • Mechanisms of residual stress removal are explored. • Over-aging treatment produces better mechanical properties. Direct aging treatment is an important post-processing procedure, yet little research has been done on how it balances the mechanical properties and the stress removal for selective laser melted (SLMed) AlSi10Mg alloys. Here, we proposed a typical direct aging treatment on SLMed AlSi10Mg alloys, and studied the effects on their microstructure, properties and residual stress evolution. The results indicate that the as-built microstructure is mainly composed of fine cellular α-Al and reticulated Si phases, and some pre-existing precipitates and dislocations are found in these cells. The direct aging treatment promotes the precipitation of the nano-scaled Si phase and preserves the network-like Si structure. Therefore, the strength of the peak-aged alloy increases while the ductility decreases. As the aging temperature increases from 160 to 200°C, aging hardening behavior was accelerated significantly. Aging at 160 °C for 4-9 h removes 32.0%-43.0% of the residual stress, which is attributed to the decomposition of the supersaturated α-Al matrix, the precipitation of the nano-Si phase and the exposure of low-angle grain boundaries (LAGBs). Considering the overal alloy performance obtained, over-aging at 160°C for 4 h is the optimized heat treatment regime. Under this condition, the yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) of the alloy in the transverse and longitudinal direction are 309.5 MPa, 464.4 MPa and 8.3% and 286.4 MPa, 464.9 MPa and 5.1%, respectively.

Improved Corrosion Resistance Behaviour of AlSi10Mg Alloy due to Selective Laser Melting

The corrosion behaviour of AlSi10Mg alloy produced by selective laser melting (SLM) under two different atmospheres, namely argon and nitrogen, was compared to that of AlSi10Mg alloy that had been cast. The present study demonstrates the systematic electrochemical behaviour of selective-laser-melted (SLMed) AlSi10Mg. Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behaviour, illustrating the degrading features of SLMed AlSi10Mg alloy in 0.1 M NaCl solution. The corrosion resistance of AlSi10Mg produced using selective laser melting was found to be 2–3 times greater than that of AlSi10Mg that had been cast. The degradation behaviour was also explained by SEM analysis of the corroded samples of SLMed AlSi10Mg and as-cast AlSi10Mg alloy. It may be deduced that the better corrosion resistance of AlSi10Mg produced through selective laser melting is due to the fast cooling rate associated with the solidification of AlSi10Mg alloy fabricated through selective laser melting, compared with the slow cooling rate associated with the solidification of AlSi10Mg produced by casting.

Surface quality improvement at selective laser melting AlSi10Mg by optimizing single point diamond turning parameters

Abstract Selective laser melting allows aluminum-silicon alloy mirrors further lightweight for aerospace applications. The reflective surfaces based on Selective laser melting aluminum-silicon alloy substrates are commonly machined by single point diamond turning. However, many surface defects on single point diamond turning machined surfaces may limit their direct applications in optical system. In the paper, single point diamond turning parameters (cutting depth, feed rate, and cutting speed) are optimized orderly to improve its surface quality. The single point diamond turning machined surface morphologies are measured by using white light profilometer. In our selective laser melting AlSi10Mg substrate, scratches and holes mainly damaged single point diamond turning surface. Scratches are caused by inclusions while holes are generated by gas pores and inclusions. Single point diamond turning parameters optimization reduces the density of such surface defects, but these defects cannot be eliminated totally.

Characterization of plasma electrolytic oxidation coatings containing carbon nanotubes formed on selective laser melted AlSi10Mg alloy

In this study, plasma electrolytic oxidation (PEO) coatings containing carbon nanotubes (CNTs) were prepared on selective laser melted (SLM) AlSi10Mg alloy by adding CNTs to the electrolyte during PEO treatment. The mechanism of doping CNTs into PEO coatings and the morphology of the resultant PEO coatings were mainly investigated. The corrosion and wear/tribological resistance of PEO coatings with CNT addition were examined by electrochemical experiments and dry sliding wear. The results indicate that: the addition of CNTs resulted in a dense outer layer composed of γ-Al2O3, and the inner layer was a porous layer composed of amorphous Al2O3 and amorphous SiO2. In addition, the CNTs significantly increased the hardness and wear resistance of the PEO coatings formed on the SLM AlSi10Mg alloy.

Comparatively evaluating the room and high temperature mechanical properties of AlSi10Mg alloy produced by selective laser melting

This work deals with the room and high-temperature mechanical properties of selective laser melted (SLMed) AlSi10Mg alloy through conducting compression testing method in a wide range of temperatures (25–450 °C) under the strain rate of 0.001s−1. The mechanical properties have been compared with those obtained for thixo-cast A356 alloy and AlCuMg2Si in-situ composite at the same thermomechanical condition. The SLMed AlSi10Mg alloy represented a substantially higher fracture toughness especially at low-temperature regime. Where AlCuMg2Si in-situ composite was fractured at 250 °C; and thixocast A356 alloy at 150 °C, the SLMed AlSi10Mg alloy tolerated high amount of strain at room temperature and experienced flow stress softening at 150 °C and 250 °C. The SLMed alloy possessed higher compressive yield strength than other samples at all test temperatures. The peak strains were expectedly decreased with the increase in temperature, however, the SLMed alloy kept its stability almost up to 350 °C. The softening fraction remained relatively constant (<14%) up to 250 °C and then suddenly increased to 22% by further temperature increment to 350 °C which may indicate the change in governing softening mechanisms. The degree of barreling was lower in the case of SLMed AlSi10Mg alloy which meant a higher ability of strain accommodation and capability for strain distribution, which was consistent with high imposed strain tolerated at various temperatures.

Effect of artificial aging on the strength, hardness, and residual stress of SLM AlSi10Mg parts prepared from the recycled powder

This study investigated the effect of artificial aging on the hardness, strength, and residual stress of SLM (Selective Laser Melting) AlSi10Mg parts prepared from recycled powder used for 30 SLM printing cycles. First, an analysis was conducted for a comparison of recycled and virgin powders; it revealed that the powders have the same shape and phase and chemical composition. The only significant differences were the slightly increased average particle size and higher oxygen content in the recycled powder, especially on the powder surface. Typical molten pools were found in the microstructure, and a fine cellular type of structure was observed. The peripheral areas of the molten pools contained coarser cells with an average size of 0.6 μm2, and the middle part of the molten pools contained finer cells with an average size of 0.17 μm2. Fine Si precipitates with an average size of 25 nm were observed inside the cells. In terms of microstructure, no significant differences were observed when compared to the published data relating to SLM using virgin powders. This suggests that recycled powder after 30 printing cycles can be utilized for SLM component preparation to achieve cost-effectiveness. However, comparison of products with the use of virgin and recycled powders showed that the use of recycled powder affects the submicron characteristics (precipitate size increase), density and the resulting mechanical properties. Artificial aging of samples from the recycled powder at 170 °C caused an increase in hardness, Young's modulus and strength, while ductility remained essentially the same after aging. Peak values of hardness and strength were determined after 6 h of artificial aging. The increase in strength of the prepared samples can be explained by the precipitation of fine Si particles and their coarsening inside the cells. However, after longer aging times, the precipitates continued to coarsen, coalesced and displayed a plate-like shape, which led to the reduction in strength. The residual stress measured by the bridge curvature method (BCM) showed a significant decrease with increasing artificial aging time. The lowest residual stress was determined for an aging time of 100 h; however, the difference between residual stress for 6–7 h and 100 h was not significant. In order to obtain higher strengths and remove internal stresses after SLM during one heat treatment, the most suitable time for artificial aging at 170 °C seems to be 6 h.

Effect of direct aging and annealing on the microstructure and mechanical properties of AlSi10Mg fabricated by selective laser melting

PurposeThis paper aims to systematically investigate the effect of the heat treatment process parameters on the microstructure and mechanical properties of the selective laser melting (SLM) AlSi10Mg alloy.Design/methodology/approachThe samples with very low porosity were fabricated with optimized processing parameters on a self-developed SLM system. The heat treatment of using the temperature of 170°C∼400°C and the holding time of 0.5∼12 h was studied, and the evolution of the microstructure and mechanical properties of AlSi10Mg alloy under direct aging and annealing was investigated and obtained.FindingsAfter annealing above 300°C for 1 h, the dendrite Si in the sample occurs spheroidization, and the molten pool contour becomes blurred or even disappeared completely, but low-temperature heat treatment does not change the morphology and size of grains significantly. Except for holding at 200°C for 1 h, all other heat treatment processes cause the tensile and yield strengths of SLM AlSi10Mg alloys to decrease and the elongation to increase. When the annealing temperature is higher than 200°C, the higher the temperature and the longer the holding time, the more obvious this effect is.Originality/valueThe correlation between the mechanical properties and microstructure of SLM AlSi10Mg alloy under different conditions was obtained. According to the characteristics of SLM forming, the direct aging and annealing process are mainly studied, which provided new information for the heat treatment of SLM AlSi10Mg alloy and promoted the engineering application of SLM AlSi10Mg alloy.

Achieving superior mechanical properties of selective laser melted AlSi10Mg via direct aging treatment

• Refined and homogenized cell structure was obtained after direct aging. • No obvious grain growth was observed after aging treatment. • Strength along building direction was significantly improved after aging. • The growth of defects was related to the formation of high energy zones. For additive manufactured aluminum alloys, the inferior mechanical properties along the building direction have been a serious weakness. In this study, an optimized heat treatment was developed as a simple and effective solution. The effects of direct aging on microstructure and mechanical properties along the building direction of AlSi10Mg samples produced via selective laser melting (SLM) were investigated. The results showed that, compared with the conventional heat treatment at elevated temperatures, direct aging at temperatures of 130–190 °C could retain the fine grain microstructure of SLM samples and promote further precipitation of Si phase, however, the growth of pores occurred during direct aging. With increasing aging temperature, while finer cell structures were obtained, more and larger pores were developed, resulting in decreased density of the samples. Two types of pore formation mechanisms were identified. Considering the balance between the refinement of cell structure and the growth of pores, aging at 130 °C was determined as the optimized heat treatment for SLM AlSi10Mg samples. The tensile strength along the building direction of the 130 °C aged sample was increased from 403 MPa to 451 MPa, with relatively high elongation of 6.5%.

The Effect of Laser Focus Shift on the Morphology of Melt Pool and Microstructure in Selective Laser Melting AlSi10Mg

Selective Laser Melting (SLM) enables to fabricate complex freeform geometries parts from computer models. In this paper, the effect of laser focus shift on the morphology, surface quality, grain size and texture of the SLMed AlSi10Mg was studied. Deep melt pool was found in 0 mm laser focus shift, while shallow and wide melt pool were found in-1.5 mm and +1.5 mm laser focus shift. The proportion of high angle grain boundaries in 0mm laser focus shift sample is the biggest han that in-1.5mm and +1.5mm. Height has a maximum value of 338 μm in +1.5 mm laser focus shift. The maximum Arithmetic average height is 33.5 μm in +1.5 mm laser focus shift. When the laser focus shift is 0 mm, the average grain diameter has a minimum grain diameter of 4.9 μm. {001}&lt;100&gt; cubic texture was found in sample fabricated by +1.5 mm laser focus shift rather than 0 mm and-1.5 mm laser focus shift.

Porosity, microstructure and mechanical property of welded joints produced by different laser welding processes in selective laser melting AlSi10Mg alloys

The welding process has been recently introduced to join of the materials fabricated by powder bed fusion (PBF) additive manufacturing (AM) to meet the requirement for the large parts and their repair in service. However, one of the main issues is the high susceptibility to the hydrogen pores occurred during fusion welding of the PBF aluminum (Al) alloys. Autogenous laser welding of a selective laser melting (SLM) AlSi10Mg alloy was firstly carried out in comparison with the casting AlSi10Mg alloy to examine the hydrogen pore characteristics. Single-pass welding with filler powders and laser melting deposition (LMD) welding were then performed on SLM AlSi10Mg alloys to reduce the hydrogen pores. The porosity, microstructure, microhardness and tensile property of the welded joints were investigated. As a result, a high susceptibility to hydrogen pores of SLM AlSi10Mg alloys is occurred in the weld metal (WM) of the welded joint produced by autogenous laser welding and single-pass laser welding due to the high hydrogen content pre-existing in the base metal (BM). However, LMD welding has been shown to effectively reduce the pore size and the porosity generated in the WM of SLM AlSi10Mg alloys. The laser welding of SLM AlSi10Mg alloys produces lower hardness and ultimate tensile strength (UTS) than that of the BM. However, the LMD welding of SLM AlSi10Mg alloys achieves higher hardness and UTS than those of the autogenous laser welding and single-pass laser welding, which is attributed to the refined microstructures and the reduced hydrogen pores in the WM.

Effect of chloride ion concentration on corrosion process of selective laser melted AlSi10Mg with different heat treatments studied by electrochemical noise

The effect of chloride ion concentration on corrosion behavior of selective laser melted (SLMed) AlSi10Mg with different heat treatment (300 °C and 400 °C) was in-situ investigated by electrochemical noise (EN) technique and corrosion morphology observation. The EN signals were analyzed by noise resistance (Rn) analysis, wavelet analysis and recurrence quantification analysis (RQA). It was found that the corrosion rates of as-building and heat treated at 300 °C samples are close at the corrosion early stage when exposed to 0.1 M NaCl, while the corrosion resistance of the sample heat treated at 300 °C is lower than that of as-building sample during the whole test period when exposed to 1 M NaCl. Corrosion resistance of the sample heat treated at 400 °C is lowest in the two NaCl solutions. The relationship between the microstructures and the corrosion mechanisms is discussed. The main contribution of present study is to provide an alternative EN technique to in-situ study the corrosion behavior of SLMed AlSi10Mg and obtain some useful information, which is different from that obtained by traditional polarization curve and electrochemical impedance spectroscopy.

Significance of plasma electrolytic oxidation treatment on corrosion and sliding wear performances of selective laser melted AlSi10Mg alloy

In this investigation, Plasma Electrolytic Oxidation (PEO) process was used to prepare an alumina (Al 2 O 3 ) coating for corrosion and wear protection of a Selective Laser Melted (SLM) AlSi10Mg alloy radiator. The phase compositions, microstructures, mechanical properties, corrosion properties and wear resistance of the SLM AlSi10Mg alloy and the PEO coatings were investigated systematically. It was observed that the AlSi10Mg alloy prepared by SLM displayed a denser microstructure, finer grains and excellent mechanical properties with an average ultimate tensile strength of 402 MPa and an elongation of 9.9%. In addition, a double-layered coating with Al 2 O 3 as the top layer having a thickness of ~20 μm and a hardness of 1051HV 0.01 was realizable on the SLM AlSi10Mg alloy by PEO treatment. The corrosion current density and wear rate of the PEO Al 2 O 3 coatings were 5.7 and 279.3 times lower compared to the plain SLM AlSi10Mg alloy. The results indicate that the PEO treatment can significantly improve the wear and corrosion resistance of the AlSi10Mg alloy prepared by the SLM process. • AlSi10Mg alloy prepared by SLM exhibits dense microstructure and fine grain size. • AlSi10Mg alloy prepared by SLM process has excellent mechanical properties. • PEO film has dense outer layer and less dense inner one whose main phase is γ-Al 2 O 3. • PEO can provide excellent corrosion and wear protection for the SLM AlSi10Mg parts.

Effect of supporting structure design on residual stresses in selective laser melting of AlSi10Mg

Residual stress is a key indicator to measure the forming quality of selective laser melting (SLM) components, and its control method has received extensive attention. As an auxiliary structure for forming SLM components, the structural characteristics of the supporting structure will affect the residual stress distribution of the formed parts. Therefore, it is extremely meaningful to explore the influence of the supporting structure design on the residual stress of SLM AlSi10Mg alloy. In this study, an approach is proposed to select and design the supporting structure for forming SLM components with different structural characteristics to achieve the purpose of reducing the residual stress in the overhanging structure of the components. As the result shows, when the contact area of single supporting tooth structure and component overhanging structure is 0.25mm2 and the X/Y interval of main supporting structure is 2.5mm, the forming effect is relatively good. Furthermore, the block supporting structure is more suitable for the overhanging structure which has small areas and less height, and the contour support is more suitable for the overhanging structure with larger area.