Selective Laser Melted AlSi10Mg Alloy Research Articles

Analysis of phase, microstructure, and mechanical characteristics of selective laser melted AlSi10Mg alloy after post-heat treatment

Analysis of phase, microstructure, and mechanical characteristics of selective laser melted AlSi10Mg alloy after post-heat treatment

Effect of Processing Parameters on Tensile Properties and Microstructure of Selective Laser Melted AlSi10Mg Alloy

Effect of Processing Parameters on Tensile Properties and Microstructure of Selective Laser Melted AlSi10Mg Alloy

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.

On the cyclic deformation behavior and correlated damage mechanism of selective laser melted AlSi10Mg alloy holding different initial microstructures

The present work deals with the cyclic deformation behavior of AlSi10Mg alloy fabricated through selective laser melting. Toward this end, the printed material was heat treated and was tested through strain-controlled push–pull fatigue under different strain amplitudes. The highest strengths were recorded for the direct aged, as-built and solutionized microstructures, respectively. The directly aged microstructure was characterized by the transformation of the columnar solidified structure into the equiaxed one and formation of the nano-Si precipitates. This was led to the best fatigue performance where an outstanding balance between the fatigue life and strength level was recorded. The low aspect ratio of the melt pools intensified the Marangoni effect, therefore, caused concentration of the material flow on the wetting side. This led to crack initiation and propagation at the end of the melt pools and formation of balling defects. Balling defect was characterized as the initiation site in the case of as-built and directly aged specimens, the cone-like geometry of which resulted in crack path deflection and a better fatigue performance. For solution treated microstructure, the melt pools were dissolved and the lack of fusion holding a critical size and located close to the surface, was characterized as the main crack initiation site.

Effect of laser power on microstructure and mechanical properties of selective laser melted AlSi10Mg alloy

Selective laser melting technology has the advantages of high machining precision, complex forming structure, short processing time, and low cost. In this work, the effect of laser power on the microstructure and mechanical properties of AlSi10Mg alloy formed by SLM was studied. The density, microhardness, and elongation of SLMed AlSi10Mg alloy increased with the increase of laser power, while the tensile strength and yield strength increased first and then decreased.

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.

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.

Crystal plasticity modeling on the selective laser melted AlSi10Mg alloy

Additive manufacturing (AM) has been developing into a revolutionary technique, in which parts are created by additive processing as opposed to the conventional subtractive manners. AM components possess the characterization of special microstructure and porosity. In this paper, a computational method is developed to investigate the mechanical property of selectively laser melted (SLM) AlSi10Mg alloy. The DREAM.3D software is utilized to generate a polycrystal model based on electron backscatter diffraction (EBSD) results. The investigated alloy shows a weak texture that the grain preferential grows along the <100> orientation. The real defect geometries are reconstructed from X-ray Computed Tomography (XCT) experimental slices and embedded into a representative volume element (RVE) model. Furthermore, a crystal plasticity (CP) model integrated fast Fourier transform method (FFT) in Düsseldorf Advanced Material Simulation Kit (DAMASK) package is implemented to simulate the mechanical response for the RVE model. The effect of porosity on tensile strength is studied, and result shows the defects degrade tensile strength.

Influence of laser process on the porosity-related defects, microstructure and mechanical properties for selective laser melted AlSi10Mg alloy

Influence of laser process on the porosity-related defects, microstructure and mechanical properties for selective laser melted AlSi10Mg alloy

Variations in microstructure and mechanical properties of selective laser melted AlSi10Mg alloy with different heat treatments

In the present study, the variations of precipitated phases, microstructure and mechanical properties of different heat treatments were investigated. The main precipitated phases were Al and Si in different heat-treated specimens. The horizontal microstructures of as-deposited and below 280°C annealing appeared the interwoven structures, and the vertical microstructures were fish-scale structures. As the annealing temperatures were higher than 280°C, the interwoven and fish-scale structures disappeared because the Si phase precipitated and coarsen along the boundaries. With regard to the specimen was heat-treated by solution + artificial aging (T6), the strengths increased and ductility decreased, respectively compared with those of specimens at 420°C for 2 h. Moreover, The AlSi10Mg specimen annealing at 280°C for 2 h has excellent strength and ductility. This investigation indicates that the microstructure and mechanical properties of SLM AlSi10Mg alloy be tailored by different heat treatment processes.

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.

Effect of Internal Pores on Fatigue Properties in Selective Laser Melted AlSi10Mg Alloy

Effect of Internal Pores on Fatigue Properties in Selective Laser Melted AlSi10Mg Alloy

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.

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.

In situ X-ray imaging of fatigue crack growth from multiple defects in additively manufactured AlSi10Mg alloy

Defects introduced during additive manufacturing currently control fatigue resistance and lead to a large scatter in lifetime, with pancake shaped lack of fusion (LOF) defects being particularly potent. In this study the fatigue crack propagation life of selective laser-melted (SLM) AlSi10Mg alloy is considered in cases where single cracks and multiple cracks can initiate from LOF defects under high cycle fatigue (HCF). Firstly, the aspect ratios of initially long fatigue cracks were determined for critical LOF defects obtained from X-ray CT renderings using the critical defect regularization method, and the response surface method used to obtain the stress intensity factor of the crack front quickly and continuously. Then a single crack propagation model considering the evolution of the crack aspect ratio established to predict the crack propagation life which is in good agreement within in situ X-ray CT imaging of the crack front when a single crack is dominant. The crack propagation phase was predicted to represent 35–60% of the total fatigue life representing a larger fraction at high stress amplitudes. Multiple cracks were found to initiate cracks at the larger stress amplitudes. In cases where multiple cracks arise this is non-conservative and so a synergistic multiple fatigue crack growth (smFCG) model was developed based on multiple defects measured a priori by X-ray CT to depict the competitive cracking effect. Compared with the single crack model, the smFCG model predicts a shorter propagation life (by 5–10%) when multiple defects are involved since it considers all the initial defects within the crack initiation region. Given the propensity of large numbers of defects in AM material this approach may be more appropriate in many cases.

Investigation on pulsed electrolytically polished AlSi10Mg alloy processed via selective laser melting technique

Currently, the surface integrity-related issues of additively manufactured parts are limiting the potential high-end applications. The present work investigates the effectiveness of the pulsed-electropolishing technique to improve the surface integrity of aluminium alloys fabricated using the selective laser melting (SLM) technique. Due to its low density, high corrosion resistance, the aluminium alloys considerably enhance the performance of lightweight critical parts for different industrial applications. In this study, selective laser melted AlSi10Mg samples were subjected to microstructural examinations using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction technique. The microhardness and tensile properties were determined using a microhardness tester and a universal testing machine, respectively. The pulsed-electropolishing process was employed for the surface finishing of the SLM-processed AlSi10Mg samples. The effect of current density on the electropolishing of selective laser melted AlSi10Mg alloy were also investigated. The microstructures of printed samples revealed a density of greater than 99.9% and weld beads along the build direction (longitudinal) and laser scan paths perpendicular to the build direction (transverse). The microhardness, yield and tensile strength properties were similar in both as-printed conditions. The pulsed electropolishing results showed a beneficial effect of higher current density values, resulting in decreased surface roughness of the SLM-processed AlSi10Mg samples. Compared to as-printed conditions, a significant decrease in surface roughness of about ∼73.35% under optimized electropolishing conditions was noted. The material ratio curve shows that the surface topography becomes more uniform with increased current density and has lesser surface undulations for as-printed samples. The 2D line profilogram and 3D surface topography of electropolished SLM-processed samples reveal the surface finish quality characteristics. The material ratio curve aids as an effective method to assess and qualify the surface topography of electropolished samples.