HW 3

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New Jersey Institute Of Technology *

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215

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Mechanical Engineering

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Jan 9, 2024

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ME 215 Week 3 HW. Ch.2: 3, 6, 10, 11, 15, 16,21, 24, 42, 43 3. Knowledge of what four aspects and their interrelations is critical to the successful application of a material in an engineering design?  Structure  Properties  Processing  Performance 6. What are some properties commonly associated with metallic materials?  Luster  High Level Thermal Conductivity  Electrical conductivity  Ductile  Magnetic Properties 10. What are the standard units used to report stress and strain in the English system? In the metric or SI system? Stress is reported in pounds per square inch or pascal. Strain is reported in inch/inch, millimeter/millimeter, percentage. 11. What are static properties? Static properties is when forces are applied to a material is constant or close to it. 15. What are some of the tensile test properties that are used to describe or define the elastic-to-plastic transition in a material?  Young’s modulus or modulus of elasticity  Modulus of resilience  Plastic deformation  Yield point  Ductility 16. Why is it important to specify the “offset” when providing yield strength data? It is important to specify the offset when providing yield strength is because most of the material do not have a definite yield point, the offset helps us determine the amount of stress that is required to cause a permanent strain on the material. 21. What are two tensile test properties that can be used to describe the ductility of a material? Two tensile test properties that can be used to describe the ductility of a material is percent elongation and/or uniform elongation. 24. What is the toughness of a material, and how might the tensile test provide insight? Toughness or modulus of toughness is the work per unit volume that is required to permanently fracture a material. The tensile test provides insight because it encompasses strength and ductility. 42. Describe several types of dynamic loading.  Hail hitting the windshield.  Truck driving across a bridge.  Wind and rain hitting a house or building during a hurricane. 42. Why should the results of standardized dynamic tests be applied with considerable caution? The results of a standardized dynamic tests should be applied with caution because, the conditions and variables tend to change greatly, and they do not always come with a standardized data or chart. Ch.4: 2, 4,12, 13-18, 22, 28-30, 32-35,37, 39 2. What are some features that are useful in defining a phase? Some of the features that are useful in defining a phase is the composition and the definable boundaries. 4. What is an equilibrium phase diagram?

Equilibrium phase diagram is a graphic mapping of the natural tendencies of a material or material system. 1 12. What is a solubility limit, and how might it be determined? Solubility limit is defined as point at which a solute is completely dissolved in the solution without the formation of the second phase of the solution. Solubility limit is determined of the solution moving to second phase by x-ray or microscopy. 13. Describe the conditions of complete solubility, partial solubility, and insolubility. Complete solubility would be two solids or liquids that completely dissolve with each other, partial solubility would be two solids or liquids that dissolve with each other up to a certain point or limit or saturation points and insolubility would be two liquids or solids or a liquid or solid that are totally insoluble with each other. 14. What types of changes occur upon cooling through a liquidus line? A solidus line? A solvus line? As cooling occurs through the liquidus line at first the 2 materials form a even dissolved liquid solution, then in the solidus line we get a even dissolved single crystalline lattice solid and in the solvus line is the mixture of 2 phases. 15. What three pieces of information can be obtained for each point in an equilibrium phase diagram? The three pieces of information from each point on the equilibrium phase diagram is temperature, pressure, and the composition of the material. 16. What is a tie-line? For what types of phase diagram regions would it be useful? A tie line is simply, and isothermal line drawn through the point of consideration, terminating at the boundaries of the single-phase regions on either side. 2 It would be useful for the consideration of the composition of the material phase of the diagram region. 17. What points on a tie-line are used to determine the chemistry (or composition) of the component phases? The points on a tie line are used to determine the composition of the phase, for example the tie line that intersects the liquidus shows the percentage composition of the liquid phase, and the point that intersects the solidus shows the percentage composition of the solid. 18. What tool can be used to compute the relative amounts of the component phases in a two-phase mixture? How does this tool work? The tool we can use is the tie line to create the lever-law calculations. Percent composition of a liquid in an alloy = α − S 2 L 2 − S 2 x 100% . 22. What is the general form of a eutectic reaction? Liquid 1 separates into solid 1 and solid 2. 28. In what form(s) might intermetallic compounds be undesirable in an engineering material? In what form(s) might they be attractive? Intermetallic compounds would be undesirable when it is present in large quantities along the grain boundaries in a continuous form, and it would be attractive when it is distributed in small unnoticeable particle size. 29.What are the four single phases in the iron–iron carbide diagram? Provide both the phase diagram notation and the assigned name. Iron: delta-ferrite - BCC Austenite- FCC Ferrite-BCC Iron-carbide – cementite 30. What features of austenite make it attractive for forming operations? What features make it attractive as a starting structure for many heat treatments? 1 (J.T. Black, 2019) 2 (J.T. Black, 2019)

The feature that makes austenite attractive in the forming operation is its lattice form of Face-centered- cubic structure. For purposes of heat treatment its low strength, high ductility and chemical uniformity. 32. Which of the three-phase reactions in the iron–carbon diagram is most important in understanding the behavior of steels? Write this reaction in terms of the interacting phases and their composition. The three-phase reaction in iron-carbon diagram is the conversion of austenite to the two phase iron- ferrite and carbide mixture. Austenite (.77% carbon) = Ferrite (.02% Carbon) + Cementite (6.67% carbon) 33. Describe the relative ability of iron to dissolve carbon in solution when in the form of austenite (the elevated temperature phase) and when in the form of ferrite at room temperature. Iron changing from austenite to ferrite it rejects the excess carbon and forms cementite which leads to a mixture made of ferrite and cementite. 34. What is pearlite? Describe its structure. Pearlite is a mixture of cementite and ferrite and it has a lamellar or a layered structure. 35. What is a hypoeutectoid steel, and what structure will it assume upon slow cooling? What is a hypereutectoid steel, and how will its structure differ from that of a hypoeutectoid? Steels having less than the eutectoid amount of carbon or .77% are called hypoeutectoid steels as hypo means less than. Upon cooling its structure enter a ferrite and austenite stable phases which then leads to formation of proeutectoid and pearlite. Hypereutectoid means more than eutectoid which means more than .77% carbon in its structure. Hypoeutectoid differs from hyper because it is cementite structure. 37. In addition to iron and carbon, what other element is present in rather large amounts in cast iron? Silicon is the element that is present in large amounts in cast iron in addition to iron and carbon. 39. What are the two possible high-carbon phases in cast irons? What features tend to favor the formation of each? Two high carbon phases in cast iron is graphite and cementite. Graphite is slow cooling, high in carbon, high silicon, presence of elements such as phosphorous, sulfur and aluminum. Cementite is fast cooling, low in carbon, thin sections, has a alloy composition of titanium, vanadium, zirconium, and chromium.

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