Powder Metallurgy

Questions & Answers

Question 8. Using Pauling's equation (in Chapter 2), compare the percent covalent character of the following compounds: hafnium carbide (HfC), titanium carbide (TiC), tantalum carbide (TaC), boron carbide (BC), and silicon carbide (SiC).(5 points)


When using the table saw how high should the blade be set?


What safety gear should be used when operating the table saw?


Question 7. The nose cap and the wing leading edges of the space shuttle may reach temperatures of up to1650°C. (a) Would the silica fiber compound (HRSI) be a suitable candidate for these sections of the shuttle?(b) If not, select a suitable material for this location. (c) List the important properties of the selected material that satisfy the design needs.(5 points)


Question 2. HFO2 has the CaF2 crystal structure. Calculate the density of HfO2 in kg/m³ if the ionic radii are Hf** = 0.083 nm and O2 =0.132 nm. (4 points)


What is a kerf and what does it matter in woodworking?


(a) Why is the Fe-Fe3C phase diagram a metastable phase diagram instead of a true equilibrium phase diagram? (1 points) (b) Define the following phases that exist in the Fe-Fe3C phase diagram: (i) austenite, (ii) a ferrite, (iii)cementite, (iv) 8 ferrite. (2 points) (c) Write the reactions for the three invariant reactions that take place in the Fe-Fe3C phase diagram. (3points)


Question 4. An austenitized 4340 standard steel bar is cooled at different rates (see Figure 2).Predict what will be the constituents in the microstructure of the bar at 200°C for the following cooling rates:(6 points) (a) 5°C/s (51-mm from the quenched end of a Jominy bar) (b) 8°C/s (19.0-mm from the quenched end of a Jominy bar) (c) 50°C/s (9.5-mm from the quenched end of a Jominy bar)


What is a fence?


Question 5. A metal-matrix composite (MMC) is made of a 6061-Al alloy matrix and continuous boron fibers.The boron fibers are produced with a 15.5 um diameter tungsten-wire core that is coated with boron to make a final 107 um diameter fiber. A unidirectional composite is made with 63 vol % of the boron fibers in the Al6061 matrix. Assuming the law of mixtures applies to isostrain conditions, calculate the tensile modulus of the composite in the direction of the fibers. Data are EB = 370 GPa, Ew = 410 GPa, and EAI = 70.4 GPa. (5 points)


Question 6. Calculate the average molecular weight Mm for a thermoplastic that has the following weight fractions fi for the molecular weight ranges listed:(5 points)


Question 3. Figure 1 illustrates the deformation mechanisms in polymers. (4 points) (a) Which mechanism is dominant in the stretching of a rubber band? (b) Which mechanism(s) represent plastic deformation? (c) Which mechanism is pronounced in polyethylene above its glass transition temperature? (d) Which mechanism is associated with the highest elastic modulus?


What is a miter?


What is kickback and how should one avoid it?


List the similarities and differences of forging and compacting metal powders.(Graduate students only)


Describe the features of a screw extruderand its functions.


Are there applications in which you, as a manufacturing engineer, would not recommend a PM product? Explain.


Compare thermoplastics and thermosets in terms of material properties and its effect on the possible manufacturing process that can be used to create parts from each material.


Describe the blow molding process in terms of its steps, capabilities, type of materials used, and final products.


Why is there density variation in the compacting of powders? How is it reduced?


Explain why the mechanical and physical properties of PM parts depend on the powder distribution, shape, and size.


The axisymmetric part shown in the accompanying figure is to be produced from fine copper powder and is to have a tensile strength of150 MPa. Determine the compacting pressure and the initial volume of powder needed 25Dimensions in mm해야12-20→25


Explain why in rotational modeling we only can create thin-walled parts.


Name the various methods of powder production and list what is the major features for each method.


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