Study of Different Aging Conditions for Analysis of Microstructure and Mechanical Properties of F357 Alloy Fabricated in LPBF Printer

Aluminum F357 is a widely used material for casting in aerospace and additive manufacturing industry. Heat treatments are commonly applied to some aluminum alloys to modify its properties. With a further study on the aging and performance of the F357 with 3D printing technology, several industries benefit of this, military, automotive and aerospace are some examples, because the numerous components casted in service. This work presents mechanical properties of F357 specimens fabricated with EOS technology and subjected to heat treatments. Heat treatments conditions were applied to tensile specimens and tested. Furthermore, the specimens were subjected to artificial thermal aging for 100 h and 1000 h at two different temperatures (285 ºF and 350 ºF), and their mechanical properties were also determined. Finally, remarks on the comparison between the heat treatments and the effect of thermal aging on the microstructures and mechanical properties of the specimens will be presented.Mechanical Engineerin

A comparison of the mechanical behavior of AlSi7Mg alloy produced through additive manufacturing and subjected to different heat treatment and aging conditions

The versatility and adaptability of Aluminum F357 (AlSi7Mg) make it a popular material in the aerospace and defense industries. In this study, two different laser powder bed fusion systems, EOS M290, and SLM 280HL were used to create specimens of Aluminum F357. These specimens were subjected to five different heat treatments: As-built, stress relief (SR), hot isostatic pressing (HIP), T6, and HIP+T6) as per ASTM F3318-18 standard. The printed specimens were then reduced to tensile bars through machining and tested for mechanical properties as per ASTM E28 using an MTS Landmark tensile testing system. In addition to the mechanical behavior analysis, the study used a JEOL JSM-IT500 SEM to observe and document the fracture produced by the tensile test and a Qness 30 CHD Master+ microhardness testing system to obtain hardness (HV) values of the alloy. The results showed that specimens fabricated in the Z direction had a tendency for higher yield strengths of approximately 225 MPa and although these results were similar between LPBF systems some variances can still be seen. However, these differences between the LPBF systems were observed to be partially mitigated by heat treatments. In conclusion, this study highlights the significance of heat treatment on the mechanical properties of Aluminum F357. The results provide valuable information for the aerospace and defense industries to optimize their processes and produce high-quality components. The compatibility of LPBF system fabrication and the mitigation of differences observed between LPBF machines by heat treatments, further demonstrate the potential of this method for producing high-quality Aluminum F357 components.Mechanical Engineerin

UHECR as Decay Products of Heavy Relics? The Lifetime Problem

The essential features underlying the top-down scenarii for UHECR are discussed, namely, the stability (or lifetime) imposed to the heavy objects (particles) whatever they be: topological and non-topological solitons, X-particles, cosmic defects, microscopic black-holes, fundamental strings. We provide an unified formula for the quantum decay rate of all these objects as well as the particle decays in the standard model. The key point in the top-down scenarii is the necessity to adjust the lifetime of the heavy object to the age of the universe. This ad-hoc requirement needs a very high dimensional operator to govern its decay and/or an extremely small coupling constant. The natural lifetimes of such heavy objects are, however, microscopic times associated to the GUT energy scale (sim 10^{-28} sec. or shorter). It is at this energy scale (by the end of inflation) where they could have been abundantly formed in the early universe and it seems natural that they decayed shortly after being formed.Comment: 11 pages, LaTex, no figures, updated versio

Binder Jetting of 316L process simulation tools evaluation

Binder Jetting has become one of the most popular Additive Manufacturing technologies over the years due to its low cost and fast production times, nevertheless this technology has a steep learning curve due to the shrinkage induced to parts during sintering. Since shrinkage is not uniform along the part, it’s hard to efficiently determine what areas will be distorted hence this needs to be taken into consideration when designing a new part and many iterations need to be printed until dimensional accuracy is achieved, as a result production time and cost significantly increase. New Binder Jetting simulation tools are being developed and tested; this software will help the technology be more robust and user-friendly for the industry. The software computes a sintering simulation and can provide displacement results making support positioning more efficient, in addition, newer versions of the software can export a compensated model which will be able to be sintered without supports. To evaluate the simulation software, a dimensional test artifact model was designed and printed, then compared with the software predicted model simulation results. The simulation software was used in an initial evaluation of the test artifact geometry to identify areas of concern in the model and document them so efficiency when predicting material behavior during the sintering process can be evaluated. In addition, an evaluation of the effects of different sintering process parameters on the physical and mechanical properties of the material will be analyzed considering the inert sintering atmosphere of the process. Finally, printing parameters of the machine such as layer thickness, binder saturation, and recoat speed among others will also be evaluated.Mechanical Engineerin

Comparison of Multiple Heat Treatments by Observing Mechanical Properties and Microstructure of LPBF Fabricated Aluminum F357

In this paper, Aluminum F357 (AlSi7Mg), a material which is widely used in the automotive, aerospace, and additive manufacturing industries, will be analyzed after performing several heat treatments to enhance the properties of the material. However, there is currently no standard for the usage and heat treating of F357 alloy; for that reason, ASTM F3318 standard will be followed for heat treating it. Having a comprehensive study on the performance of 3D-printed F357 benefits the automotive, military and aerospace industries due to the numerous casted components already in service and many becoming legacy components. This work presents mechanical and microstructural properties of F357 specimens fabricated with SLM technology and subjected to heat treatments; as-built, stress-relief, T6, hot isostatic pressing (HIP), and HIP+T6 heat treatments were applied. Furthermore, with the interest of the alloy performance in- service conditions, the specimens were subjected to artificial thermal aging.Mechanical Engineerin

A comprehensive and comparative study of microstructure and mechanical properties for post-process heat treatment of AlSi7Mg alloy components fabricated in different laser powder bed fusion systems

AlSi7Mg (F357) alloy specimens were fabricated in two different laser powder bed fusion (LPBF) systems: EOS M290 and SLM 280HL. Vertical (Z) and horizontal (XY) orientations were fabricated, and five different thermal post processes were applied to samples, individually. According to ASTM F3318-18, the considered thermal conditions were as-built, stress relieved (SR1), HIP, T6 and HIP+T6. Subsequently, the individual samples were aged at 140 °C and 177 °C for 100 h and for up to 1000 h. Tensile specimens were machined down from the aged samples and tested as per ASTM E8/E8M-21. While the yield stress (YS), elongation (%), and Vickers microindentation hardness (HV) were somewhat different for the as-built components, the general trends for the different heat treatments were essentially the same. As-built and SR1 treated microstructures were dominated by microdendritic cells, while the HIP, T6 and T6 + HIP component microstructures consisted of recrystallized grains containing eutectic Si particles of various sizes and shapes within the grain interiors and the grain boundaries; which gave rise to wide-ranging mechanical properties. As an example of these widely-ranging mechanical properties, it was observed that components fabricated in the Z or build direction in the EOS system exhibited a YS, elongation, and HV of 225 MPa, 13%, and HV120, while when HIPed and unaged exhibited values of 87 MPa, 25%, and HV51, respectively. These same HIPed components when aged at 177 °C for 1000 h exhibited values of 81 MPa, 41% and HV44. The mechanical properties of the unaged, HIPed and aged fabricated in Z direction in SLM system were 85 MPa, 31%, HV51, and 80 MPa, 42%, and HV47, respectively, providing support for LPBF system fabrication compatibility. These measured mechanical property values represent a small fraction of the more than 1600 mechanical property measurements (YS, UTS, elongation, and hardness (HV)) in this study