Solucionario Grovr

Solutions for Fundamentals of Modern Manufacturing, 3/e (published by Wiley) © MPGroover 2007

6 METALS
Review Questions
6.1 What are some of the general properties that distinguish metals from ceramics and polymers? Answer. Typical metallic properties include: high strength and stiffness, good electrical and thermal conductivity, and higher density than ceramics or polymers. 6.2 6.3 6.4 Whatare the two major groups of metals? Define them. Answer. Ferrous metals, which are based on iron; and nonferrous, which includes all others. What is an alloy? Answer. An alloy is a metal comprised of two or more elements, at least one of which is metallic. What is a solid solution in the context of alloys? Answer. A solid solution is an alloy in which one of the metallic elements is dissolved inanother to form a single phase. 6.5 Distinguish between a substitutional solid solution and an interstitial solid solution. Answer. A substitutional solid solution is where the atoms of the dissolved element replace atoms of the solution element in the lattice structure of the metal. An interstitial solid solution is where the dissolved atoms are small and fit into the vacant spaces (theinterstices) in the lattice structure of the solvent metal. 6.6 What is an intermediate phase in the context of alloys? Answer. An intermediate phase is an alloy formed when the solubility limit of the base metal in the mixture is exceeded and a new phase, such as a metallic compound (e.g., Fe3C) or intermetallic compound (e.g., Mg2Pb) is formed. 6.7 The copper-nickel system is a simple alloy system, asindicated by its phase diagram. Why is it so simple? Answer. The Cu-Ni alloy system is simple because it is a solid solution alloy throughout its entire composition range. 6.8 6.9 What is the range of carbon percentages which defines an iron-carbon alloy as a steel? Answer. The carbon content ranges from 0.02% to 2.11%. What is the range of carbon percentages which defines an iron-carbon alloy ascast iron? Answer. The carbon content ranges from 2.11% to about 5%. 6.10 Identify some of the common alloying elements other than carbon in low alloy steels. Answer. The common alloying elements in low alloy steel are Cr, Mn, Mo, Ni, and V. 6.11 What are some of the mechanisms by which the alloying elements other than carbon strengthen steel. Answer. All of the alloying elements other than Cstrengthen the steel by solid solution alloying. Cr, Mn, Mo, and Ni increase hardenability during heat treatment. Cr and Mo improve hot hardness. Several of the alloying elements (Cr, Mo, V) form hard carbides with C, which increases wear resistance. Vanadium inhibits grain growth during heat treatment which improves strength and toughness.
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Solutions for Fundamentals of ModernManufacturing, 3/e (published by Wiley) © MPGroover 2007

6.12 What is the mechanism by which carbon strengthens steel in the absence of heat treatment? Answer. In the absence of heat treatment, carbon strengthens steel by creating a two-phase structure in the metal. 6.13 What is the predominant alloying element in all of the stainless steels? Answer. Chromium. 6.14 Why is austenitic stainless steelcalled by that name? Answer. It is called austenitic because this alloy exists in its austenitic phase at room temperature. The reason is that nickel has the effect of enlarging the austenitic temperature range to include room temperature. 6.15 Besides high carbon content, what other alloying element is characteristic of the cast irons? Answer. Silicon. 6.16 Identify some of the properties for...