Additive Manufacturing (AM) processes are gaining prominence in industry as they can build parts to near-net-shape with minimal postprocessing. Metal laser AM techniques, such as Selective Laser Melting (SLM), offer rapid cooling rates on the order of 10^5-10^6 K/s. This is due to a highly-focused laser heating a microscopic volume in an otherwise lower-temperature environment. Hence, metal laser AM can manufacture novel, out-of-equilibrium microstructures that cannot be produced in near-net-shapes with other processes. It is desirable to optimize feedstocks for metal AM processes to leverage their advantages. One option of optimizing feedstocks is through in-situ alloying, or by using elemental powders. Elemental powders homogenize over the course of multiple laser passes, or intrinsic heat treatments. However, rapid cooling rates prevent the homogenization of a layer when first printed. To investigate the homogenization process, this thesis used synchrotron X-ray Diffraction (sXRD) to track the phase transformations during the SLM of a 14-layer single wall (single-hatch, multilayered) of Ti-1Al-8V-5Fe (Ti-185) from elemental Ti, Fe and an alloyed AlV powders, capturing frames at 250 Hz. Infrared imaging was performed simultaneously on the surface at 1603.5 Hz to observe the temperature changes at the surface. Post-mortem electron microscopy was performed on cross-sections of the wall perpendicular to the scanning direction to observe the changes in the microstructure with respect to the build direction. Specifically, Electron Dispersive X-Ray Spectroscopy and Electron Backscatter Diffraction were performed to observe the alloying elemental distribution and microstructure of the wall with respect to the build direction. The research performed found that in the melted zone, phase transformation times below 50 ms yielded a partially-alloyed microstructure, with regions concentrated and dilute in alloying elements. Partial mixing was diffusion-induced by laser beam heat and the exothermic heat of mixing of Ti-185 from its constituent elements. Further diffusion during reheating cycles yielded an alloyed microstructure. / Thesis / Master of Applied Science (MASc)

It’s well known that MnAl(C) material consists of a metastable phase (τ) with promising ferromagnetic properties, produced either by controlled cooling from the high-temperature hexagonal ε-phase or rapid cooling that freezes the ε-phase followed by low-temperature annealing. Due to the high cooling rates involved, additive manufacturing (AM) especially selective laser melting (SLM), has been identified as a possible method to retain the high-temperature ε-phase, hence containing a potential capacity to produce permanent magnets upon low-temperature annealing. Moreover, the competency of additive manufacturing to address manufacturing design complexity, material scarcity and tailored properties, yields a great opportunity to produce permanent magnets with suitable magnetic properties for complex applications. This work provides a systematic study on three main aspects; development of printing parameters for improved relative density of as-printed MnAl(C) samples; investigation of the influence of scanning strategies on the crystallographic texture of as-printed and annealed samples; investigation of the influence of annealing time and temperature on τ-phase purity and magnetic properties. It was found that laser remelting (multiple laser exposure) combined with specific scanning strategies is a promising path to enhance the relative density of as-printed samples. Some specific scanning strategies were found to be capable of retaining relatively strong crystallographic textured ε-phase in as-printed samples. Following the annealing process for ε→τ transformation, only a partial transformation of crystallographic texture was observed. Characterization of annealed samples through XRD (x-ray diffraction) and phase fractions calculations through Rietveld refinement reveals that relatively short annealing times and low temperatures result in incomplete ε→τ transformation. In addition, longer annealing times and higher temperatures surpass the complete ε→τ transformation and lead to the formation of equilibrium phases subsequently reducing the magnetic performance. Furthermore, the experimental findings demonstrated a pronounced influence of higher carbon content in the powder, resulting in improved magnetic properties.

Additive manufacturing (AM) is an emerging and interesting technology that enables some of theproduct development projects (PDPs) to produce products that have mechanical and tribologicalproperties comparable to products that are conventionally manufactured. Selective laser melting(SLM) is an additive manufacturing technology that is predominantly used for the production of metalbased components (i.e. it could be pure metal, alloys, and metal matrix composites). This workevaluates and ranks two different steel grades produced with SLM technology in tribological andcutting tool applications at AB Sandvik Coromant. The two steel grades used in this work were Cofree maraging steel alloy and Co-free W360 AMPO alloy. Both the grades are Cobalt free, hencedeveloped as a sustainable alternative for the future. The W360 AMPO alloy is a hot-work tool steelwith high temperature wear resistance and heat resistance. The work covers the characterization ofmicrostructure and chemical composition, mechanical properties, and tribological properties toevaluate the performance of the tool steel grades when used as tool bodies in drilling applications.The microstructure and chemical composition of the additive manufactured and heat-treated tool steelswere analyzed using SEM and EDS. The mechanical properties were evaluated using micro-Vickersindentation and scratch testing while the tribological properties were evaluated using pin-on-disctesting where counter material used was quenched and tempered steel. The application test included asimulated chip wear test using chip breakers (CB’s) and an actual drilling test, both performed at ABSandvik Coromant. To study the effect of surface topography on the adhesion tendency, the simulatedchip wear test was performed on both milled and grounded chip breaker (CB) samples. The drillingtest was done with three different test-set ups; function test, 30° inclined exit, and forced tool life test.The cellular microstructure was observed on Co-free maraging steel alloy sample, while themicrostructure was tempered martensite in W360 AMPO alloy. Elemental analysis revealed thechemical composition of the two steel grades. The measured hardness for both the samples Co-freemaraging steel alloy and W360 AMPO was found to be within the specification of demands (50-52HRC), although the hardness of W360 AMPO was a bit higher than Co-free maraging steel alloy. Theresults of the pin-on-disc tests showed that the wear resistance of the W360 AMPO alloy issignificantly higher than that of the Co-free maraging steel alloy, the tribo-system used was similarwhen compared to the actual application. Also, after analyzing the pin made up of quenched andtempered steel 34CrNiMo6 (SS2541) it can be seen that due to the W360 AMPO sample the volumeloss of the pin is almost 4 times when compared to Co-free maraging steel alloy. The result from thesimulated chip wear test showed that W360 AMPO has better wear characteristics. Adhesion ofworkpiece material (SS2541) was observed on both samples. In the simulated chip wear test, thesurface topography effect was studied by performing a test on milled and grounded CBs. GroundedCBs showed less adhesion tendency compared with milled CBs on both samples but the wearcharacteristics were similar irrespective of the surface roughness. The result from the drilling testshowed wear scar was predominant on a drill with Co-free maraging steel alloy and a drill with W360AMPO alloy was intact. Future possible investigations proposed after findings from experimentalresults may lead to future work.

An experimental study of several variants of radius and strut angle of the body centered cubic unit cell was performed to determine the mechanical properties and failure mechanisms of the mesostructure. Quasi static compression tests were performed on an Instron® universal testing machine with a 50kN load cell at 0.2mm/min. The test samples were built using a SLM Solutions 125 selective laser melting machine with 316L stainless steel. Test specimens were based on 5mm cubic unit cells, with a strut diameter 10% of the unit cell size, with skins on top and bottom to provide a cantilever boundary constraint. Specimens were inspected for dimensional accuracy using precision calipers and inspected for morphology using a MicroVu® macroscope. The compressive properties of the mesostructure was compared to the compressive properties of macrostructure. The BCC unit cell behaves significantly different at the boundary layer of a constrained lattice. The failure mode at the boundary is characterized by plastic bending within the microstruts while the non boundary layer cells fail via plastic bending at the node. Manufacturing compensation parameters were determined for part shrinkage and droop. Two predictive numerical models were developed, based on the Gibson-Ashby model of cellular solids, as well as a finite element model. Numerical results did not agree well with the experimental results, indicating that the droop observed on the structures significantly affects the mechanical properties of the overall structure. The 25% radius cubic unit cell and 3^3 lattice withstood the greatest stress of all specimens tested and exhibited nearly ideal plastic deformation behavior.

No description available.

<p> Laser powder bed fusion (LPBF) is a rapidly emerging manufacturing technology capable of producing complex part geometries through the repeated, precise laser melting of metallic powder layers. At present, the process is primarily employed in high-value-added applications which exist in the aerospace, biomedical, and dental industries. As industrial implementation of LPBF has matured, research has focused on established materials for which there are already large bodies of literature and regulatory approval, such as Inconel 718, Inconel 625, Ti-6Al-4V, and 316 stainless steel. However, the rapid solidification process inherent to LPBF leads to vastly different microstructures with improved strength compared to these traditional materials in cast or wrought forms. In general, the high solidification velocity and thermal gradients result in cellular and dendritic solidification structures with finer grain and precipitate sizes than conventionally processed alloys. These microstructure changes warrant the exploration of new alloy systems and reevaluation of historically cast compositions with optimized microstructures, especially considering the tunability of a digitally controlled fabrication process. This work examines laser powder bed fusion of Mar-M 509, a carbide-strengthened cobalt alloy that is typically investment cast directly into complex-shaped components such as nozzle guide vanes (NGVs). NGVs are stationary components in gas turbine engines for propulsion and energy production which require strength under moderate mechanical loading at high temperatures. Investment cast microstructures have porosity defects in slower-cooled regions due to lack of liquid feed to interdendritic regions. As-printed, the cellular and dendritic Mar-M 509 LPBF microstructures lead to the formation of continuous, fiber-like, eutectic carbide structures in the intercellular and interdendritic regions, which limit macroscopic ductility. Thermo-Calc is used for calculation of phase diagrams (CALPHAD) to estimate the equilibrium transformation temperatures of MC, M23C6, and M7C3-type carbides, which informs design of isothermal heat treatments to engineer microstructures with enhanced ductility over the as-printed or cast versions of Mar-M 509 while maintaining tensile strength. Scanning and transmission electron microscopy reveals the composition and distribution of carbide phases as a function of heat treatment temperature. Lastly, heat treatment recommendations for nozzle guide vanes are made.  </p>

The selective laser melting (SLM) process allows for the control of unique part form and function characteristics not achievable with conventional manufacturing methods and has thus gained interest in several industries such as the aerospace and biomedical fields. The fabrication processing parameters selected to manufacture a given part influence the created material microstructure and the final mechanical performance of the part. Understanding the process-structure and structure-performance relationships is very important for the design and quality assurance of SLM parts. Image based analysis methods are commonly used to characterize material microstructures, but are very time consuming, traditionally requiring manual segmentation of imaged features. Two Python-based image analysis tools are developed here to automate the instance segmentation of manufacturing defects and subgranular cell features commonly found in SLM 316L stainless steel (SS) for quantitative analysis. A custom trained mask region-based convolution neural network (Mask R-CNN) model is used to segment cell features from scanning electron microscopy (SEM) images with an instance segmentation accuracy nearly identical to that of a human researcher, but about four orders of magnitude faster. The defect segmentation tool uses techniques from the OpenCV Python library to identify and segment defect instances from optical images. A melt pool structure generation tool is also developed to create custom melt-pool geometries based on a few user inputs with the ability to create functionally graded structures for use in a virtual testing framework. This tool allows for the study of complex melt-pool geometries and graded structures commonly seen in SLM parts and is applied to three finite element analyses to investigate the effects of different melt-pool geometries on part stress concentrations. / Master of Science / Recent advancements in additive manufacturing (AM) processes like the selective laser melting (SLM) process are revolutionizing the way many products are manufactured. The geometric form and material microstructure of SLM parts can be controlled by manufacturing settings, referred to as fabrication processing parameters, in ways not previously possible via conventional manufacturing techniques such as machining and casting. The improved geometric control of SLM parts has enabled more complex part geometries as well as significant manufacturing cost savings for some parts. With improved control over the material microstructure, the mechanical performance of SLM parts can be finely tailored and optimized for a particular application. Complex functionally graded materials (FGM) can also easily be created with the SLM process by varying the fabrication processing parameters spatially within the manufactured part to improve mechanical performance for a desired application. The added control offered by the SLM process has created a need for understanding how changes in the fabrication processing parameters affect the material structure, and in turn, how the produced structure affects the mechanical properties of the part. This study presents three different tools developed for the automated characterization of SLM 316L stainless steel (SS) material structures and the generation of realistic material structures for numerical simulation of mechanical performance. A defect content tool is presented to automatically identify and create binary segmentations of defects in SLM parts, consisting of small air pockets within the volume of the parts, from digital optical images. A machine learning based instance segmentation tool is also trained on a custom data set and used to measure the size of nanoscale cell features unique to 316L (SS) and some other metal alloys processed with SLM from scanning electron microscopy (SEM) images. Both these tools automate the laborious process of segmenting individual objects of interest from hundreds or thousands of images and are shown to have an accuracy very close to that of manually produced results from a human. The results are also used to analyze three different samples produced with different fabrication processing parameters which showed similar process-structure relationships with other studies. The SLM structure generation tool is developed to create melt pool structures similar to those seen in SLM parts from the successive melting and solidification of material from the laser scanning path. This structural feature is unique to AM processes such as SLM, and the example test cases investigated in this study shows that changes in the melt pool structure geometry have a measurable effect, slightly above 10% difference, on the stress and strain response of the material when a tensile load is applied. The melt pool structure generation tool can create complex geometries capable of varying spatially to create FGMs from a few user inputs, and when applied to existing simulation methods for SLM parts, offers improved estimates for the mechanical response of SLM parts.

Additive Manufacturing (AM) using the Powder Bed Fusion (PBF) is a relatively new manufacturing method that is capable of creating shapes that was previously practically impossible to manufacture. Many think it will revolutionize how manufacturing will be done in the future. This thesis is about some aspects of when and how to Design for Additive Manufacturing (DfAM) when using the PBF method in metal materials. Designing complex shapes is neither easy nor always needed, so when to design for AM is a question with different answers depending on industry or product. The cost versus performance is an important metric in making that selection. How to design for AM can be divided into how to improve performance and how to improve additive manufacturability where how to improve performance once depends on product, company and customer needs. Using advanced part shaping techniques like using Lattices or Topology Optimization (TO) to lower part mass may increase customer value in addition to lowering part cost due to faster part builds and less powder and energy use. Improving PBF manufacturability is then warranted for parts that reach series production, where determining an optimal build direction is key as it affects many properties of PBF parts. Complex shapes which are designed for optimal performance are usually more sensitive to defects which might reduce the expected performance of the part. Non Destructive Evaluation (NDE) might be needed to certify a part for dimensional accuracy and internal defects prior use. The licentiate thesis covers some aspects of both when to DfAM and how to DfAM of products destined for series production. It uses design by Lattices and Topology Optimization to reduce mass and looks at the effect on part cost and mass. It also shows effects on geometry translation accuracies from design to AM caused by differences in geometric definitions. Finally it shows the effect on how different NDE methods are capable of detecting defects in additively manufactured parts.

Additive manufacturing (AM), or 3D-printing, allows for rapid prototyping and complex design and gives an insight into how customers may use recent technology to co-create value. Metal additive manufacturing reaching market maturity broadens the playing field for the ability to create personalized products. The idea of value co-creation places customers in the center. However, there is a lack of knowledge about how customers engage in collaborative processes where aesthetics and embodied experiences manifest with the development of new products. By empirically researching the phenomenon in the field of technology and understanding the roles of aesthetics, customer-centered approaches to innovation may become more fruitful. This research applies technology entrepreneurship studies with aesthetics, more specifically the embodied processes that occur during the value co-creation of complex technology. A 4-month micro-ethnography of an AM firm was conducted to explore the aesthetics of value co-creation. Expanding on the work of Elias et al. (2018) and Aarikka-Stenroos and Jaakkola (2012), value co-creation in a complex technology field was explored. The key insight in this thesis is that customers may come with valuable contributions during the commercialization of technology, not only when trying to make sense of the technology, but also insights into where the technology may be applied.

This thesis investigates the differences in the design process when developing a product for additive manufacturing (AM) compared to traditional manufacturing methods, such as CNC machining. In recent years, additive manufacturing (AM), including metal-based laser powder bed fusion (L-PBF), has gained popularity, leading to increased adoption by companies. The design process for AM, particularly in the context of metals, differs compared to for traditional manufacturing methods. L-PBF, being a method based on highly concentrated laser beam fusion, offers a higher level of design freedom, enabling the creation of intricate shapes, internal structures, and varying wall thicknesses. In contrast, traditional manufacturing methods based on subtractive processes impose limitations on design possibilities due to tooling and machining constraints. Adapting to L-PBF requires designers to reconsider, re-think and redesign parts specifically for AM, taking into account factors suchas cost, knowledge requirements and build volume limitations. The application of L-PBF extends to various industries, including aerospace and performance automobiles. Designing for L-PBF opens up new possibilities for product development by leveraging the advantages of AM, such as design flexibility and topology optimization. Topology optimization allows for the creation of lightweight components while maintaining structural integrity. However, transitioning from traditional manufacturing to L-PBF presents challenges, requiring designers to navigate the unique considerations and constraints associated with AM. This research aims to enhance the understanding of the design process for AM, with a specific focus on L-PBF, and its implications for product development. By exploring the differences between AM and traditional manufacturing methods, this study contributes to the broader adoption and effective implementation of AM technologies in various manufacturing sectors. / Detta arbete undersöker skillnaderna i designprocessen vid utveckling av produkter för additive manufacturing (AM) jämfört med traditionella tillverkningsmetoder, såsom CNC bearbetning. På senare år har additiv tillverkning (AM), inklusive Laser Powder Bed Fusion (L-PBF), blivit populärt och allt fler företag använder sig av tekniken. Designprocessen för AM, skiljer sig jämnfört med för traditionella tillverkningsmetoder. L-PBF erbjuder en hög grad av designfrihet och möjliggör avancerade former, interna strukturer och varierande väggtjocklekar. I kontrast begränsar traditionella tillverkningsmetoder, som bygger på subtraktiva processer, designmöjligheterna på grund av verktygs- och bearbetningsbegränsningar. Att anpassa sig till L-PBF kräver att designers omprövar och omdesignar delar specifikt för AM och tar hänsyn till faktorer som kostnad, kunskapskrav och begränsningar i byggvolymen. Användningen av L-PBF sträcker sig till olika branscher, inklusive luft- och rymdindustrin samt prestandabilar. Att designa för L-PBF öppnar upp nya möjligheter för produktutveckling genom att utnyttja fördelarna med AM, såsom designflexibilitet och topologioptimering. Topologioptimering möjliggör skapandet av lätta komponenter samtidigt som den strukturella integriteten bibehålls. Övergången från traditionell tillverkning till L-PBF innebär dock utmaningar och kräver att designers hanterar de unika övervägandena och begränsningarna som är förknippade med AM. Denna forskning syftar till att förbättra förståelsen för designprocessen för AM, med särskilt fokus på L-PBF, och dess implikationer för produktutveckling. Genom att utforska skillnaderna mellan AM och traditionella tillverkningsmetoder bidrar denna studie till en bredare användning och effektiv implementering av AM-teknologier inom olika tillverkningssektorer.