Powder Metallurgy and Reaction Kinetics Quiz
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Questions and Answers

Which material is most commonly used in PBF processing?

  • Nylon Polyamide (correct)
  • Titanium
  • Stainless Steel
  • Cemented Carbide

    • LPS involves the complete melting of all powder particles in the processing method.

    False

    What role does Co (cobalt) play in traditional powder metallurgy?

    It acts as a lower-melting-point constituent that glues together particles of WC.

    In full melting processes, thermal energy from subsequent scans can re-melt portions of the previously __________ solid structure.

    <p>solidified</p> Signup and view all the answers

    Match the following properties with their corresponding concepts:

    <p>LPS = Fusion of powder particles with some molten Full Melting = Complete melting of materials PBF processing = Selective Laser Sintering WC = Tungsten Carbide</p> Signup and view all the answers

    Which factor leads to an increase in the rate constant according to the Arrhenius equation?

    <p>Decrease in activation energy</p> Signup and view all the answers

    The activation energy of a catalyzed reaction is higher than that of an un-catalyzed reaction.

    <p>False</p> Signup and view all the answers

    What is the rate constant when the temperature is 289K, the activation energy is 200kJ/mol, and the pre-exponential factor is 9 M-1s-1?

    <p>6.37X10^-36 M-1s-1</p> Signup and view all the answers

    In chemically-induced sintering, a by-product is formed which binds the powder together during _______ reactions.

    <p>thermally-activated</p> Signup and view all the answers

    What is a common characteristic of chemically-induced sintering that often necessitates additional processing?

    <p>Part porosity</p> Signup and view all the answers

    Match the following reactions with their products formed during laser processing:

    <p>SiC + O2 = SiO2 composite ZrB2 + O2 = ZrO2 composite Al + N2 = AlN composite</p> Signup and view all the answers

    Liquid-Phase Sintering is considered the least versatile mechanism for Powder Bed Fusion.

    <p>False</p> Signup and view all the answers

    The equation used to find the new temperature in the Arrhenius equation is ln(k1/k2) = -[Ea/R](1/T1 - 1/T2). Fill in the blank: Ea in this equation represents _______.

    <p>activation energy</p> Signup and view all the answers

    Which mode of scanning is focused on scanning the outline of the part cross-section?

    <p>Contour mode</p> Signup and view all the answers

    In fill mode, there is a preferential direction for the residual stresses induced by scanning.

    <p>False</p> Signup and view all the answers

    What must any powder delivery system for PBF be capable of transporting?

    <p>The correct volume of powder from the powder reservoir to the build platform.</p> Signup and view all the answers

    A powder delivery system must have a powder reservoir of sufficient _____ to build to the maximum build height.

    <p>volume</p> Signup and view all the answers

    Match the characteristics of powder handling with their implications:

    <p>As particle size decreases = Interparticle friction and electrostatic forces increase When surface area to volume ratio increases = Surface energy increases and becomes more reactive When handled, small particles = Tend to become airborne and float Smaller powder particle sizes = Enable better surface finish and higher accuracy</p> Signup and view all the answers

    Which of the following is NOT a characteristic for powder feeding systems?

    <p>Create excessive shear forces</p> Signup and view all the answers

    Randomized scanning patterns are sometimes used to achieve a uniform layer.

    <p>True</p> Signup and view all the answers

    What is one outcome of using smaller powder particle sizes in PBF?

    <p>Better surface finish</p> Signup and view all the answers

    Which of the following thermal sources is NOT used in Powder Bed Fusion processes?

    <p>Oxygen torch</p> Signup and view all the answers

    Thermoset polymers can effectively be processed using Powder Bed Fusion technology.

    <p>False</p> Signup and view all the answers

    What is the main purpose of using nitrogen gas in the PLS process?

    <p>To minimize oxidation and degradation of the powdered material.</p> Signup and view all the answers

    The pLS process typically fuses layers of powder that are __________ thick.

    <p>0.075 - 0.1 mm</p> Signup and view all the answers

    Match the material types with their descriptions:

    <p>Thermoplastic = Can be melted and reshaped Thermoset = Degrades and does not melt Ceramics = Compounds consisting of metal oxides or nitrides Composites = Materials made from two or more different constituents</p> Signup and view all the answers

    Which material is commonly processed in PBF and is known as nylon?

    <p>Thermoplastic polymer</p> Signup and view all the answers

    The build platform in the PLS process is often cooled down after part formation.

    <p>True</p> Signup and view all the answers

    Name one type of metal that has been processed and is commercially available through PBF.

    <p>Stainless steel</p> Signup and view all the answers

    The process of adding and smoothing powder layers in PBF is facilitated by a __________ roller.

    <p>counter rotating</p> Signup and view all the answers

    Which of the following is NOT a characteristic of Powder Bed Fusion processes?

    <p>Incorporation of a cooling system</p> Signup and view all the answers

    What materials are commonly used in polymer laser sintering (pLS) machines?

    <p>Nylon polyamide and other polymers</p> Signup and view all the answers

    Electron Beam Melting (EBM) uses laser technology to melt metal powder particles.

    <p>False</p> Signup and view all the answers

    Name one advantage of using Nd-YAG lasers in polymer laser sintering.

    <p>Better absorptivity for metal powders</p> Signup and view all the answers

    The primary difference between EBM and SLM lies in their respective energy sources: EBM uses ________ while SLM utilizes ________.

    <p>electron beam, laser beam</p> Signup and view all the answers

    Match the following terms with their correct descriptions:

    <p>Selective Laser Sintering (SLS) = A method for directly processing polymers Polymer Laser Sintering (pLS) = Uses CO2 lasers for polymer processes Electron Beam Melting (EBM) = Fusion through a high-energy electron beam 3D Micromac = Uses a powder feed system for metal parts</p> Signup and view all the answers

    What type of environment do polymer laser sintering machines work in?

    <p>Nitrogen atmosphere with low oxygen</p> Signup and view all the answers

    Laser-based systems can directly process pure metals and ceramics.

    <p>False</p> Signup and view all the answers

    What is one common use of aluminum oxide powders in machining?

    <p>Production of parts using Electron Beam Melting</p> Signup and view all the answers

    What is a key requirement for EBM to function effectively?

    <p>Low-partial-pressure vacuum environment</p> Signup and view all the answers

    A laser beam is affected by the presence of gas in the same way as an electron beam.

    <p>False</p> Signup and view all the answers

    What is one drawback of powder-based additive manufacturing compared to liquid-based processes?

    <p>Inferior accuracy and surface finish</p> Signup and view all the answers

    The build materials in PBF typically exhibit _____ shrinkage, which can lead to part distortion.

    <p>3-4%</p> Signup and view all the answers

    Match the following approaches to line- and layer-wise PBF processing with their descriptions:

    <p>Mask-based sintering = Technique that utilizes a mask for selective heating Absorptivity-enhancing agent = Enhances absorption in part regions Sintering inhibitor outside part region = Prevents sintering effects in surrounding areas Loose powder support material = Used for supporting polymer part building</p> Signup and view all the answers

    Which factor contributes to better accuracy in PBF materials?

    <p>Lower thermal conductivity</p> Signup and view all the answers

    The accuracy of powder-based additive manufacturing is influenced only by the operating conditions.

    <p>False</p> Signup and view all the answers

    What makes the future of PBF processes promising?

    <p>Wide variety of materials and common usage in AM technologies</p> Signup and view all the answers

    What is one of the primary approaches to controlling material state in extrusion-based systems?

    <p>Using temperature to liquefy the material</p> Signup and view all the answers

    Using a chemical change to cause solidification does not apply to biomedical applications.

    <p>False</p> Signup and view all the answers

    Name one method of solidification that can occur in an extrusion-based system.

    <p>Curing agent, drying of material, or reaction with air.</p> Signup and view all the answers

    In Fused Deposition Modeling (FDM), materials are extruded in a __________ state before solidification.

    <p>molten</p> Signup and view all the answers

    Which of the following is a limitation of FDM?

    <p>Limited material types available</p> Signup and view all the answers

    Match the extrusion processes with their specific characteristics.

    <p>Gel formation = Bioextrusion application Melt extrusion = Used for thermoplastics Scaffold architectures = Support for tissue engineering Contour crafting = Large-scale construction technology</p> Signup and view all the answers

    Contouring crafting is primarily used for small-scale applications.

    <p>False</p> Signup and view all the answers

    What is a significant requirement for materials used in bioextrusion?

    <p>Biocompatibility with living cells.</p> Signup and view all the answers

    Study Notes

    Chapter 6: Extrusion-Based Systems

    • Extrusion-based systems are a type of additive manufacturing (AM) technique.
    • Extrusion-based systems use temperature or chemical changes to control the material state, producing material by forcing a liquefied material through a nozzle.
    • Some methods rely on a continuous supply of material, while others use pellets or powders.

    Objectives

    • Discuss extrusion-based systems
    • Describe basic principles (material loading, liquefaction, extrusion, solidification, bonding, and support generation).
    • Analyze plotting and path control.
    • Explain Fused Deposition Modeling (FDM) from Stratasys, including machine types.
    • Identify materials used in extrusion.
    • Discuss the limitations of FDM.
    • Describe bioextrusion techniques (gel formation, melt extrusion, scaffold architectures).
    • Explore other extrusion-based systems (contour crafting, nonplanar systems, FDM of ceramics, Reprap).

    Materials

    • Materials suitable for extrusion-based AM are varied, including polymers (thermoplastics and some thermosets), metals, and ceramics.
    • Biocompatible materials are well-suited to medical applications in extrusion.
    • Specific material properties (viscosity, melting point, thermal stability) influence the selection of appropriate processes and equipment for extrusion.

    Basic Principles

    • Material loading: Materials can be loaded using methods such as pellet feeding, powder feeding, or continuous filament input.
    • Liquefaction: Temperature or chemical reactions are used to liquefy the material to make possible bonding and printing.
    • Extrusion: The liquefied material is forced through a nozzle under pressure.
    • Solidification: Depending on the material, solidification can be due to cooling, curing, reacting with air, or drying.
    • Bonding: During extrusion, bonding between the deposited material and the preceding layers determines the overall strength and structural integrity.
    • Support generation: This involves creating supportive structures within the 3D print to maintain part integrity, which are fabricated or designed to be removed later.
    • Plotting and path control: This involves defining the deposition path and shape of the final part, which can have an impact on the structural strength of the material.

    Fused Deposition Modeling (FDM)

    • FDM is a widely used extrusion-based technique, commonly used in polymer 3D printing processes.
    • FDM machines use a heating chamber to liquefy the filament.
    • A variety of FDM machines from Stratasys and other manufacturers are available and vary in build volume and other features. Some are aimed at the general engineering market and some at niche applications.

    Extrusion Principles

    • Some extrusion methods employ the extrusion of a heated, molten material, whereas others use a solidified or gel structure.
    • Extruders are equipped with a nozzle to direct the flow of extruded material.
    • Pressure is exerted by a screw or other mechanisms to move the material through the nozzle.

    Limitations of FDM

    • Depending on the size and shape of the part, some distortion, shrinkage, and other manufacturing defects can occur.
    • Build speed can impact accuracy in some cases.

    Scaffold Architectures

    • Proper spacing between extruded structures is important for tissue engineering scaffolds to allow cell growth.
    • Porosity or the proportion of space between scaffold struts is critical for the amount of material transport possible and the success of biological implantation.
    • Specific geometric patterns can be used to create scaffolds with different structures that may create different amounts and spaces, and thereby may help with the process of cell or tissue growth.

    Other Extrusion-based Systems

    • Contour crafting: Technology is related to the contour or shape being sculpted.
    • Other systems use particular technologies or principles, including particular machines, like the Reprap and Fab@home projects.These systems use simple, low-cost 3D printing technology concepts.
    • FDM of Ceramics: This technique is used to fire and fuse similar to the FDM process.
    • Nonplanar systems: This design permits building materials at odd angles.

    Process Benefits and Drawbacks

    • Extrusion-based methods are versatile.
    • Wide range of polymer or other material choices and application possibilities.
    • Relatively low cost for entry level systems.
    • Some drawbacks could include: less precise details in the design (though it depends on the complexity).
    • Design and accuracy (including support removal) and processing times can vary significantly across these systems.

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    Related Documents

    Chapter 6 Extrusion-Based Systems PDF
    Powder Bed Fusion Processes Chapter 5 PDF

    Description

    Test your knowledge on powder metallurgy, focusing on PBF processing, the role of cobalt, and key concepts in chemically-induced sintering. Additionally, explore factors that influence reaction rates and the Arrhenius equation. This quiz covers essential topics that are fundamental to understanding the field of materials science.

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