ISE 2500 Ch 6 - Metals
What important alloy is formed from lead and tin?
Solder
Besides high carbon content, what other alloying element is characteristic of the cast irons?
Silicon
What are the three basic methods by which metals can be strengthened?
(1) alloying to form solid solutions and two-phase structures which are stronger than the elemental metals; (2) cold working, in which the strain-hardened metal is stronger and harder than the unstrained metal; and (3) heat treatment - most of the commercial heat treatments are designed to increase the strength of the metal.
The superalloys divide into three basic groups, according to the base metal used in the alloy. Name the three groups.
(1) iron-based alloys, (2) nickel-based alloys, and (3) cobalt-based alloys.
substitutional solid solution
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.
What is a solid solution in the context of alloys?
A solid solution is an alloy in which one of the metallic elements is dissolved in another to form a single phase.
What are some of the mechanisms by which the alloying elements other than carbon strengthen steel?
All of the alloying elements other than C strengthen 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.
Identify some of the properties for which aluminum is noted?
Aluminum is noted for its low density, high electrical and thermal conductivity, formability, good corrosion resistance due to the formation of a tough oxide film on its surface, and ability to be alloyed and strengthened to achieve good strength-to-weight ratios.
What is an alloy?
An alloy is a metal comprised of two or more elements, at least one of which is metallic.
What is an intermediate phase in the context of alloys?
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.
interstitial solid solution
An interstitial solid solution is where the dissolved atoms are small and fit into the vacant spaces (the interstices) in the lattice structure of the solvent metal.
What is the predominant alloying element in all of the stainless steels?
Chromium
What are the two major groups of metals? Define them.
Ferrous metals, which are based on iron; and nonferrous, which includes all others.
What is the most important engineering property of copper that determines most of its applications?
Its high electrical conductivity (low resistivity).
What are some of the noteworthy properties of magnesium?
Magnesium is noted for its very low density (lightest of the structural metals), propensity to oxidize (which can cause problems in processing), and low strength; however, it can be alloyed and strengthened by methods similar to those used for aluminum alloys to achieve respectable strength-to-weight ratios.
Why are they called noble metals?
Nobel metals are so-named because they are chemically inactive.
What does the term refractory mean?
Refractory means the capability to withstand high temperature service.
The copper-nickel system is a simple alloy system, as indicated by its phase diagram. Why is it so simple?
The Cu-Ni alloy system is simple because it is a solid solution alloy throughout its entire composition range.
What is the range of carbon percentages that defines an iron-carbon alloy as a steel?
The carbon content ranges from 0.02% to 2.11%
Identify some of the common alloying elements other than carbon in low alloy steels.
The common alloying elements in low alloy steel are Cr, Mn, Mo, Ni, and V.
What elements are traditionally alloyed with copper to form (a) bronze and (b) brass?
The elements are (a) tin and (b) zinc, respectivley.
What are some of the important applications of nickel?
The important applications of Ni are (1) as an alloying ingredient in steel, e.g., stainless steel; (2) for plating of steel to resist corrosion; and (3) to form nickel-based alloys noted for high-temperature performance and corrosion resistance.
Identify some of the important applications of zinc.
The important applications of Zn are (1) die castings - zinc is an easy metal to cast; (2) as a coating in galvanized steel; (3) as an alloying element with copper to form brass.
Name the important refractory metals
The refractory metals include columbium (Cb), molybdenum (Mo), tantalum (Ta), and tungsten (W). Mo and W are the most important.
What is so special about the superalloys? What distinguishes them from other alloys?
The superalloys are generally distinguished by their strength and resistance to corrosion and oxidation at elevated temperatures.
What are the noteworthy properties of titanium?
Titanium is noted for its high strength-to-weight ratio, corrosion resistance (due to the formation of a thin but tough oxide film), and high temperature strength.
What are some of the general properties that distinguish metals from ceramics and polymers?
Typical metallic properties include: high strength and stiffness, good electrical and thermal conductivity, and higher density than ceramics or polymers.
Why is austenitic stainless steel called by that name?
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.
Name the four principal noble metals
copper, gold, platinum, and silver