2022 Volume 63 Issue 7 Pages 1013-1020
The mechanical properties of aluminum alloys fabricated by selective laser melting (SLM) were examined with particular focus on their fatigue properties. The SLM aluminum alloys with various amounts of internal porosities were fabricated to investigate the effect of porosity on the fatigue properties. There were no remarkable differences in the microstructures of the SLM alloys. In terms of tensile properties, the tensile strength was significantly higher in the specimen with low porosity and decreased with increasing porosity. In terms of fatigue properties, crack initiations were observed at the internal pores in all specimens with the number of crack initiations increasing as a function of porosity. The fatigue strength decreased with increasing porosity, and porosity had a more significant effect on fatigue strength than tensile strength. The fatigue limit, which corresponds to the size and number of internal pores, changed remarkably in the low porosity regime because the size and number of internal pores changed drastically in this range. Considering the residual stress, these results demonstrate that by considerably suppressing the internal pores in the SLM aluminum alloys, a good fatigue performance can be expected, regardless of the occurrence of fatigue cracks at the internal pores.
This Paper was Originally Published in Japanese in J. JILM 70 (2020) 128–135.
Selective laser melting (SLM), which is a 3D printing technique, is a promising innovative tool for manufacturing metallic materials and is garnering significant attention in various industrial fields.1,2) Laser powder bed fusion is a fabrication method of SLM that is used to manufacture metallic materials. In this processing method, three-dimensional structures are molded by layering metallic powders one layer at a time, followed by repetitive melting and solidifying by using a laser beam based on the slice data acquired from 3D computer-aided design data. The microstructure of the SLM material obtained through this fabrication method exhibits specific morphology. For example, with Al–Si alloys, extremely fine cellular dendritic structures can be created and a static strength equivalent to that of a wrought material of the 2000 series can be achieved.3–7) Therefore, the SLM is expected to facilitate the practical development of structural components having a high degree of morphological freedom and superior mechanical properties.
When applying metallic materials to structural components, metal fatigue is an important property, and defects such as internal pores are known to have a strong influence on fatigue strength. Linder et al.8) examined the correlation between fatigue properties and internal pores in an AlSi10Mg alloy casting in sand and metal molds. They reported that the metal mold casting presents a higher fatigue limit than the sand mold casting because of the difference in pore distribution. Houria et al.9) examined the fatigue properties of the A356-T6 cast alloy and reported that fatigue cracks are caused by internal pores and the fatigue limit decreases as the porosity increases. A laser is typically used in the SLM of aluminum alloys. However, aluminum exhibits high thermal conductivity and poor laser absorption;10) thus, insufficiently melted powders remain, resulting in the formation of internal pores. Thus, to expand the application of SLM aluminum alloys to structural components, it is important to elucidate the influence of internal pores in the SLM material on fatigue properties, which would assure safety.
The fatigue properties of SLM aluminum alloys have been widely investigated, particularly those of AlSiMg alloys. Brandl et al.11) reported that the fatigue cracks in an SLM AlSi10Mg alloy originate from the internal pores and the stacking direction influences the fatigue properties. In addition, Ngnekou et al.12) reported that, in the same SLM AlSi10Mg alloy, the T6 thermal process would change the form of internal precipitates, improving fatigue properties. In contrast, Beretta et al.13) summarized the fatigue properties in a SLM AlSiMg alloy and reported that the number and size distribution of the internal pores of the SLM material had a notable influence on fatigue strength, wherein, as the pore sizes increased, the fatigue strength decreased. However, when assessing fatigue properties, SLM materials with a relatively large number of internal pores are often analyzed, and the influence of various factors other than pores on fatigue properties has not been widely investigated. Because momentary heating and cooling are repeated during SLM, a residual internal stress is induced that could influence the fatigue properties.14) However, the influence of residual stress on the fatigue properties of an SLM aluminum alloy has not been extensively studied.
In this study, AlSi10Mg SLM materials with almost no internal pores were prepared by optimizing the SLM condition. Moreover, laser irradiation conditions were controlled to intentionally create internal pores and several types of SLM materials with different numbers and sizes of internal pores were prepared. The as-prepared SLM materials were subjected to a fatigue test under the same test condition; the relationship between the fatigue strength, the residual stress and internal pores was systematically examined. Furthermore, the fatigue properties of the as-prepared SLM materials were compared with those of a wrought material with similar tensile strength. Based on the results, the essential fatigue properties for SLM materials were verified by quantitatively assessing each influencing factor.
The powder used for SLM was the AlSi10Mg (Al–9.9%Si–0.41%Mg–0.14%Fe (mass%)) alloy powder (mean particle diameter: 25.6 µm), which is often used as an alloy for casting. For SLM, we used EOSINT M280 (EOS, Germany). The laser equipped on this device was the Yb fiber laser (wavelength: ∼1.07 µm) with a maximum output of 400 W and spot size of ∼0.1 mm. The SLM was performed under Ar atmosphere (residual oxygen concentration: ∼0.1%), and the laser scanning direction was rotated by 67° for each layer. To match the longitudinal and stacking directions, we prepared cylindrical specimens with a diameter of 7 mm and a height of 55 mm. The base plate for SLM (A5083) was preheated to 35°C before starting the SLM by using a heater built into the platform.
SLM materials with different forms of internal pores were prepared by changing the laser irradiation conditions. The density of the SLM materials correlates with the density of the energy input to the powder layer through laser irraditaion.15,16) Energy density E (J/mm3) is expressed in terms of laser power P (W), scanning speed v (mm/s), scanning pitch s (mm), and stacking thickness t (mm):
| \begin{equation} E = P/(v \cdot s \cdot t) \end{equation} | (1) |
In this study, we used this equation as the reference and varied the irradiation conditions while maintaining a layer thickness of 0.03 mm (30 µm) to prepare four types of SLM materials. One of the SLM materials was prepared under the conditions where the relative density of the materials would be the highest (P: 300 W, v: 1200 mm/s, s: 0.15 mm, E: 55.6 J/mm3).3) For the remaining three SLM materials, we set the irradiation conditions so that the energy density would be lower than that of the optimum condition to control the internal porosities. The internal porosities in the SLM materials were assessed on the basis of the relative density. The relative density was calculated from the true density (2.67 g/cm3) of the Al–10%Si–0.4%Mg alloy and the measurement of density using Archimedes’ principle, which calculates the density from the weight and apparent volume. Table 1 shows the energy density and relative density of the four types of test specimens. The relative density of the material prepared under the optimum condition was near 100%. Notably, relative density decreases with energy density; the lowest relative density of a SLM material was ∼98%. In this study, the SLM materials are denoted on the basis of the descending order of the energy density, that is, descending the relative density, samples A, B, C, and D. In addition to SLM materials, we prepared an extruded material made of the 2024-T4 alloy with static strength equivalent to that of the AlSi10Mg alloy.
To observe the microstructure of SLM material, we used a scanning electron microscope equipped with the Schottky-type electron gun (JEOL JXA-8530F), and observed the horizontal and vertical cross-sections of the specimens. The form of internal pores was observed with an X-ray CT scan (Toshiba IT Control Systems Corporation TOSCANER-32300µFD). The observation conditions included an X-ray tube voltage of 200 kV, a tube current of 50 µA, and a spatial resolution of 8 µm. For determining the boundary between materials and pores, the threshold was changed to match the boundary line to the margin of a pore, while confirming the two-dimensional cross-section obtained with X-ray CT. By recreating the two-dimensional cross-section, we prepared three-dimensional images.
The mechanical properties of the SLM materials were evaluated using the tensile and fatigue tests. For the tensile test, we machined the cylindrical SLM materials into dumbbell-shaped specimens (diameter: 3.5 mm, length: 18 mm) and assessed its properties with a universal testing machine (INSTRON 5583, Instron). The crosshead speed was 1 mm/min, and 0.2% proof stress was calculated from a nominal stress–nominal strain curve obtained from an extensometer with a camera (iMETRUM Video Gauge 4 Lite). For the fatigue test, cylindrical SLM materials were used to prepare fatigue test specimens (grip diameter: 5 mm, notch root diameter: 2.5 mm, notch of R7, stress concentration factor α: 1.05) (Fig. 1). Its properties were assessed with a cantilever-type rotational bending fatigue testing machine (Yamamoto Metal Technos Co. Ltd., YRB200). We hung a predetermined weight on one side of a specimen, and calculated the load stress considering α. The rotational speed during the fatigue test was 3150 rpm. The residual stress of the test specimen was measured by the X-ray stress measurement device (AutoMATE, Rigaku Corporation). Setting the tube voltage and tube current as 40 kV and 40 mA, respectively, the Cr-Kα X-ray (diameter: 0.5 mm) was irradiated to the notch of the specimen and measured using the sin2 ψ technique from the diffraction intensity of Al(311). To observe the fracture surface after the fatigue test, we used a scanning electron microscope (JEOL JSM-6610).
Shape of fatigue test specimen.
Figures 2 and 3 show the microstructure on the horizontal and vertical cross-sections of each SLM material. The dark and light gray areas are the α-Al and Si crystallized phases, respectively. In the horizontal cross-section, all SLM materials were found to possess a submicron equiaxial cellular dendritic structure. However, as the energy density of the laser irradiation decreased, the structure became slightly finer. This is possibly because, under the condition of low energy density, the attained temperature during SLM is low and the cooling speed is high; thus, it resulted in a faster solidification speed and a finer structure. Conversely, the fine cellular dendritic structure was also confirmed in the vertical cross-section. The structure was not equiaxial, but elongated in the stacking direction; i.e., the direction of heat flow. However, the tendency of the structure to become slightly finer with decreasing energy density is similar to the trend observed in the structure on the horizontal cross-section. The cell size tended to decrease slightly with the decrease in the energy density.
Microstructural SEM images of samples (a) A, (b) B, (c) C, and (d) D for the horizontal cross-sections.
Microstructural SEM images of samples (a) A, (b) B, (c) C, and (d) D for the vertical cross-sections. The stacking direction corresponds to the longitudinal direction.
Figure 4 shows the distribution of internal pores in each SLM material analyzed by the X-ray CT scan. The left column shows the three-dimensional distribution of pores, whereas the right column shows the two-dimensional distribution in a horizontal cross-section at an arbitrary location. The black part represents the pores. Sample A with the highest relative density had an extremely small number of fine pores (size: ≤100 µm). As the relative density decreased, the number of pores increased. Sample D with the lowest relative density had large pores with the size of several hundred micrometers, which likely had a notable influence on the mechanical properties. In addition, in the horizontal cross-section, the distribution of pores was found to be uniform with hardly any bias. Therefore, if a test specimen is cut from these SLM materials, the influence of the porosity on the mechanical properties can be appropriately evaluated.
X-ray CT scans of samples (a) A, (b) B, (c) C, and (d) D. The left column shows 3D visualization of porosity and the right column shows CT images for the horizontal cross-sections.
Figure 5 shows the result of the tensile test of each SLM material. For comparison, we present the result for the 2024-T4 extruded material. The bar graph of each sample shows 0.2% proof stress, tensile strength, and elongation to failure. Sample A had a 0.2% proof stress of ∼245 MPa and a tensile strength of ∼470 MPa, which are extremely high. Considering that the reported 0.2% proof stress, tensile strength, and elongation to failure of die cast materials made of the same materials are 170 MPa, 325 MPa, and 3%, respectively,17) these values of Sample A are notably high. Compared to the 2024-T4 extruded material, although the elongation to failure and 0.2% proof stress are low, the tensile strength is equivalent to that of the SLM materials. This may be attributed to the fine microstructure, which is specific to SLM. Since the fatigue strength and tensile strength are generally correlated,18) we considered the use of the 2024-T4 extruded material as comparison valid. In contrast, Sample B had properties that were slightly inferior to Sample A. Furthermore, the strength and ductility decreased notably in Samples C and D. However, even Sample C, with a relative density of 98.68%, showed a value close to the die cast materials, indicating that the SLM materials have essentially superior tensile properties.
Tensile properties of samples A, B, C, and D, and 2024-T4.
Figure 6 shows the S-N curves for each SLM material and the 2024-T4 extruded material. All samples had an increasing number of cycles until failure as the stress amplitude decreased, which is a similar trend of typical S-N curves. However, variations in the fatigue strength and data are quite different among the SLM materials. First, the influence of the relative density becomes clear, confirming that the fatigue strength decreases notably with a decrease in the relative density. SLM materials B and C exhibit considerably different fatigue strengths. This may be because the relative density differs by ≥1%. When the fatigue properties of SLM materials A and B were compared, the ratio of difference in the fatigue strength was higher than that of the tensile strength. With both SLM materials, the cellular dendritic structure and crystal grain diameter slightly differ because of the difference in the laser irradiation conditions; however, this difference is minor. Thus, the influence of microstructure on the fatigue strength is likely to be limited and the difference in the number of pores has a major influence on the fatigue strength. In contrast, the fatigue strength of the 2024-T4 extruded material was considerably higher than that of SLM material A with the highest fatigue strength among all SLM materials. Next, focusing on the deviation of data, SLM materials C and D with low relative density had relatively small variations, but SLM materials A and B with high relative density had relatively large variations. In particular, SLM material A had large variations over a wide range of stress conditions. In contrast, with the 2024-T4 extruded material, variations in the data were extremely small.
S-N curves of samples A, B, C, and D, and 2024-T4.
Figure 7 shows the relationship between the fatigue limit and relative density of the SLM materials. Because non-ferrous metals such as aluminum typically do not have a clear fatigue limit,18) in this study, we used the fatigue strength at finite life of the 107th cycle as the fatigue limit. We used the relative density of the 2024-T4 extruded material as 100% (Fig. 7). The fatigue limit does not considerably change over the range of low relative density; however, near a relative density of 100%, it rapidly increased. It is therefore suggested that, in the range of high densities, the influence of internal pores on the fatigue limit is considerably strong. Although the fatigue limit of SLM material A is inferior to that of the 2024-T4 extruded material, it is still close to 200 MPa. The fatigue ratio obtained by dividing the fatigue limit with tensile strength was ∼0.4, which is similar to that of a wrought high strength aluminum alloy (fatigue ratio of 0.3–0.4).18)
Relationship between the relative density of specimens and the fatigue limit.
The residual stress of a material is considered to be another factor that influences the fatigue properties in addition to internal pores. Because SLM is a process that involves repetitive rapid melting and solidification, it is suggested that a high residual stress is induced by the internal strain owing to its process. It is well known that the residual stress influences fatigue properties. Moreover, the influence of residual stress on fatigue properties varies drastically depending on the tensile or compressive stress.18) Furthermore, residual stress changes notably with the processing method and shape of the object. Therefore, to clarify the influence of internal pores on the fatigue properties of each SLM material, we measured the residual stress of the fatigue test specimen obtained by processing a cylindrical SLM material and examined the influence of residual stress on fatigue properties.
Figure 8 shows the measurement results of the residual stress for SLM materials A and D with the highest and lowest energy densities, respectively, and the 2024-T4 extruded material. Three specimens were randomly selected for each type, the center of the notch was rotated 90° in the circumferential direction, and residual stress in the longitudinal direction was measured in four locations for each test specimen. The figure shows the residual mean and range of fluctuations, where the positive and negative sides are the tensile residual stress and compressive residual stress, respectively. In terms of SLM material A, there was hardly any residual stress. However, this result is influenced by the residual stress in locations where a SLM material with a diameter of 7 mm was cut to the dimensions of the fatigue test specimen. In addition, this result is also influenced by the surface finish of the test specimen, and is not the result of the SLM material surface before cutting. On the other hand, SLM material D had a higher compressive stress than SLM material A because of the difference in the laser irradiation conditions. In other words, as shown in the photographs of the microstructure in Fig. 2 and Fig. 3, the microstructure of SLM material D was slightly finer than that of SLM material A and this characteristic was attributable to the higher speed of heating and cooling during laser irradiation. Therefore, the temperature change during SLM was more drastic for SLM material D than that for SLM material A, leading to a higher residual stress. However, when residual stress is induced because of the heat affect, it is considered that the tensile residual stress is also induced in addition to the compressive residual stress. Under a bending load, fatigue cracks are predicted to begin near the surface; thus, in this study, although the residual stress distribution in the depth direction was not measured in the test specimen, the tensile residual stress could be induced in parts away from the surface. In addition, we did not measure the residual stress for SLM materials B and C in this study. However, based on the energy density and the observation of microstructure, it is assumed that the residual stress of SLM materials B and C fall between that of SLM materials A and D. On the other hand, the 2024-T4 extruded material exhibited the highest compressive residual stress, which increased the fatigue strength. In other words, when comparing the fatigue properties of the SLM materials, the strong influence of compressive residual stress must be adequately considered for the 2024-T4 extruded material, which is discussed in the next section.
Residual stress of samples A and D, and 2024-T4.
To investigate the influence of residual stress on the fatigue strength, the fatigue limit diagram that expresses the relationship between the mean stress of the maximum stress and minimum stress and the fatigue limit is typically used.19) However, since we used a rotational bending fatigue tester to assess fatigue properties in this study, we cannot change the mean stress by controlling the load stress. Various equations have been proposed to approximate the fatigue limit curve if it is difficult to experimentally obtain the fatigue limit curve. For example, the Goodman line which connects true fracture stress, σT, and fatigue limit of zero mean stress, σω0, with a straight line, the modified Goodman line in which σT of the Goodman line is replaced by tensile strength, σB, and the Gerber line which connects σB and σω0 with a parabola19) are typical approximation lines. However, most equations were proposed assuming the mean stress to be on the tensile side, and they cannot be applied to the compressive side. The only equation that can be used for the compressive side is the Goodman line.19) However, as the present study did not accurately measure σT, we used the modified Goodman line that is relatively similar to the Goodman line to assess the influence of the residual stress on the fatigue properties.
The modified Goodman line is an equation that predicts fatigue limit σω for each σm from σω0, σB, and mean stress σm; it is expressed as follows:19)
| \begin{equation} \sigma_{\omega} = \sigma_{\omega 0}(1 - \sigma_{m}/\sigma_{B}) \end{equation} | (2) |
In a fatigue test of rotational bending, the absolute value of the maximum and minimum stress is the same; thus, the mean stress is zero. When there is residual stress, it is subtracted from each stress; thus, the mean stress matches the residual stress. Therefore, we plotted the tensile strength of SLM material A, SLM material D, and the 2024-T4 extruded material on the horizontal axis and the fatigue limit to the position of each residual stress. This fatigue limit diagram of each material is shown in Fig. 9. The fatigue limit barely changes in SLM material A, wherein the residual stress is close to zero. With SLM material D, wherein a small amount of compressive residual stress exists, the fatigue limit slightly decreases, increasing the difference from that of SLM material A and emphasizing the influence of pores. On the other hand, the fatigue limit predicted for the 2024-T4 extruded material with the largest compressive residual stress for the zero mean stress was much lower than the experimental value obtained. This value was considerably lower than that of SLM material A. We used the modified Goodman line that was linearly approximated, but the actual fatigue limit line is often expressed with a convex curve.20) In such a case, the actual σω0 may be higher than the values predicted from the modified Goodman line. However, when considering the influence of residual stress on the fatigue test specimen, the fatigue limit of the 2024-T4 extruded material and SLM material A did not have as much difference as that in fatigue properties shown in Figs. 6 and 7. If internal pores could be suppressed to the level of SLM material A, highly superior fatigue properties can be achieved.
Fatigue limit diagram of samples A and D, and 2024-T4.
Based on these results, it is considered that the internal pore is the dominant factor that influences the fatigue properties of SLM materials. Thus, to examine the influence of internal pores in more detail, we observed the fracture surface after the fatigue test and quantitatively evaluated the pores through X-ray CT scan analysis.
Figure 10 shows the fracture surfaces of each SLM material after the fatigue test. The observed samples all fractured within the range of 106–107 cycles. The point identified with an arrow in the figure is the initiation point of the cracks. It can be seen that in all test specimens, all fatigue cracks were initiated from the internal pores. However, the characteristics of the pores that were the initiation point differ among the various types of SLM materials. In SLM material A with the least number of internal pores, the size of initiation pores was small and the initiation point was limited to one. As the number of internal pores increased within a SLM material, the size of the initiation pores increased. With SLM materials C and D, cracks initiated from multiple pores. To organize the number of initiation points in each SLM material, we showed the data of test conditions wherein there was one initiation point with an open symbol and the data of conditions with multiple initiation points with closed symbols for the S–N curves of Fig. 6 (Fig. 11). The conditions that did not lead to fracture were omitted from the figure for convenience. For SLM materials C and D, all data are denoted by closed symbols, indicating that fatigue cracks originate from multiple initiation points. In contrast, for SLM material A, all data are denoted by open symbols, indicating that the initiation point is limited to one under all conditions. With SLM material B, the result varied with test conditions. Considering the fatigue strength of 150 MPa as the limit, the initiation point became multiple at the values above and was limited to one at the values below this limit. These results are strongly reflected in the deviation width from the S–N curve; in other words, when there were multiple initiation points, the deviation width from the S–N curve was small, but when there was a single initiation point, the deviation width was relatively large. The locations of internal pores in a SLM material possibly vary significantly among each test specimen. In other words, a rotational bending test is strongly influenced by the pores near the surface; thus, in a SLM material with limited pores, pores may not be present near the surface and the variation of data will increase. In contrast, for SLM materials with a large number of pores, it is probabilistically predicted that the number of pores will increase near the surface; thus, variations in the data will decrease.
Fractured surfaces of the fatigue specimens of (a) A (σa = 200 MPa, Nf = 4.0 × 106), (b) B (σa = 120 MPa, Nf = 1.3 × 106), (c) C (σa = 50 MPa, Nf = 5.7 × 106) and (d) D (σa = 60 MPa, Nf = 2.0 × 106). The white and black arrows indicate crack initiation and the right column shows a magnified image of the crack initiation region indicated by the black arrow.
S-N curves of samples A, B, C, and D.
Next, we quantitatively analyze the pores. Based on the result of the X-ray CT scan, the internal pores were divided into 50 µm intervals and organized by size (Fig. 12). The present analytical conditions included a spatial resolution of 8 µm for the X-ray CT scan; thus, we targeted pores with the size of several dozen micrometers or larger and organized them on the basis of the sphere-equivalent diameter. SLM material A had the smallest number of pores, with distribution in smaller sizes. As the relative density of the SLM material decreased, the number of pores increased; the size was distributed over a wider range. Large pores close to 1 mm were found in SLM materials C and D. Based on these results, we obtained the relationship among the number of pores, mean diameter, and relative density (Fig. 13). The number of pores and mean diameter are expressed with their reciprocal in this figure. The number of pores and mean diameter increased with decreasing relative density. These results were extremely consistent with the relationship between the relative density and fatigue limit shown in Fig. 7. In any case, the values drastically changed over the range with high relative density. In other words, the fatigue properties of SLM materials were influenced by not only the number of pores and but also their sizes; further, there is a correlation with the occurrence of fatigue cracks confirmed by the observation of fracture surfaces.
Size distribution of internal pores in samples A, B, C, and D.
Relationship between the number and size of internal pores, and the relative density of specimens.
The fatigue limit of metallic materials is dependent on the size of internal defects such as pores. Murakami21) reported the result of the quantitative summary of the influence of defect sizes with eq. (3) using a parameter, $\sqrt{area} $:
| \begin{equation} \sigma_{\omega} = A(H_{v} + 120)/(\sqrt{\textit{area}})^{1/6} \end{equation} | (3) |
The above equation shows that as internal pores decrease, the fatigue limit increases. A hot isostatic pressing (HIP) has been used as a method to remove internal pores and is widely used in industrial applications. In particular, with SLM, because HIP can be performed while maintaining material shape, it is considered to be extremely effective as a post process. HIP has been reported to be effective in improving the mechanical properties of SLM materials. For example, Wu et al.22) reported that HIP of a SLM material of a titanium alloy considerably improves mechanical properties such as fatigue properties. In contrast, there is almost no report on the influence of HIP on the fatigue properties of the SLM materials of an aluminum alloy. Our previous studies showed that the HIP in a SLM material of the AlSi10Mg alloy would coarsen the Si particles, reducing tensile strength by less than half.23) Considering that fatigue strength is generally proportional to tensile strength, it is suggested that the fatigue strength of the SLM materials of an aluminum alloy cannot be improved by HIP.
On the other hand, internal pores do not always influence the fatigue limit. As the size of defects decreases, the fatigue limit increases; however, when the size is lower than 100 µm, the fatigue limit becomes constant.21) The transition point varies among materials, but it is usually in the range of several dozen micrometers. In other words, if pores could be suppressed to this size for SLM materials, even if there are internal pores, the influence of internal pore on fatigue limit would be limited, and would not cause any practical problems. The present result that the fatigue properties of SLM materials were similar to those of the 2024-T4 extruded material when considering the residual stress validates this argument. In the actual products, the tensile stress and torsional stress in addition to bending stress are expected to be induced; however, considering that most situations would have bending stress as the dominant stress, the present results indicate that the SLM materials of the aluminum alloy can be utilized as structural members. With this result, we hope that the technology of SLM will be expanded to the manufacturing of actual products in the future.
SLM materials of the AlSi10Mg alloy were prepared with different internal pores by SLM of the aluminum alloy to compare and evaluate the fatigue properties. The following findings were obtained:
This work was supported by a JSPS KAKENHI grant Number JP16K06808.
