Worksheet: Alloys

In this worksheet, we will practice describing the formation and applications of alloys and the effect of alloying on the properties of metals.

Q1:

Duralumin is an alloy of aluminum commonly used in aircraft construction.

What is the main alloying element in duralumin?

  • AManganese
  • BCopper
  • CIron
  • DMagnesium
  • EZinc

Why is duralumin more suitable than pure aluminum to use in aircraft construction?

  • AIt is easier to mold into complex shapes.
  • BIt is less dense and thus allows for lower fuel consumption.
  • CIt is more thermally conductive and thus allows for easier engine cooling.
  • DIt is less easily corroded by wet air.
  • EIt cracks less easily when forces are applied.

Q2:

The arrangement of a person’s teeth may be gradually altered by the attachment of a fine wire framework, known as a dental brace. Dental braces are commonly made of smart titanium alloys such as nitinol.

What is the main advantage of titanium alloys over steel for this application?

  • ALower density
  • BGreater stiffness
  • CGreater corrosion resistance
  • DLower cost
  • EGreater malleability

What is the main advantage of steel over titanium alloys for this application?

  • ALower cost
  • BGreater malleability
  • CGreater corrosion resistance
  • DLower density
  • EGreater stiffness

Nitinol is described as a smart alloy because it changes in response to a stimulus. Which stimulus affects the properties of nitinol the most?

  • AChanges in pH
  • BOxygen
  • CHeat
  • DLight
  • EWater

Why are smart alloys such as nitinol more suitable than other titanium alloys for this application?

  • AThey change shape to better fit the teeth during use.
  • BThey prevent infection of the teeth during use.
  • CThey become stiffer and more difficult to break during use.
  • DThey become more water-soluble during use.
  • EThey apply force to the teeth during use.

Q3:

A major disadvantage of shape memory alloys is their high susceptibility to metal fatigue.

Which of the following is the best definition of metal fatigue?

  • ADecrease in toughness due to repeated heating
  • BDecrease in stiffness due to repeated stretching
  • CDecrease in melting point due to repeated impacts
  • DDecrease in strength due to repeated stretching
  • EDecrease in hardness due to repeated impacts

Why are shape memory alloys more susceptible than other alloys to metal fatigue?

  • AThe alloys contain disordered structures that undergo large changes in shape when force is applied.
  • BThe alloys contain highly reactive atoms that are oxidized by air when heat is applied.
  • CThe alloys contain weakly bonded atoms that separate into pure elements when force is applied.
  • DThe alloys contain weakly bonded atoms that separate into pure elements when heat is applied.
  • EThe alloys contain flexible structures that undergo large changes in shape when heat is applied.

Q4:

Copper and aluminum are both widely used as electrical conductors. Copper wires are usually preferred for the wiring in tools and appliances. However, alloys of aluminum are more suitable for transporting electricity over longer distances in the walls of buildings and through overhead cables.

What is the main reason for using copper in electrical wiring instead of a copper alloy such as brass?

  • ALower density
  • BGreater strength
  • CLower cost
  • DGreater ductility
  • EGreater conductivity

What is the main reason for using aluminum alloys instead of copper for the wiring within the walls of a building?

  • ALower cost
  • BGreater ductility
  • CGreater strength
  • DLower density
  • EGreater conductivity

Why are aluminum alloys used instead of aluminum for the wiring in overhead electrical cables?

  • AGreater ductility
  • BGreater conductivity
  • CGreater strength
  • DLower cost
  • ELower density

Q5:

Drink cans must be manufactured, stored, and transported in very large quantities. Why is a manganese alloy of aluminum more suitable than aluminum for the construction of drink cans?

  • AHigher malleability
  • BLower cost
  • CHigher strength
  • DHigher corrosion resistance
  • ELower ductility

Q6:

Medieval cannons and cannonballs contained a range of different metals. Cannonballs were typically made of iron, but bronze was often preferred for the construction of the cannons. Compared with iron cannons, bronze cannons were found to be longer lasting, easier to cast, and able to fire cannonballs at higher speeds.

Which property of iron made it preferable to bronze for the construction of cannonballs?

  • AGreater malleability
  • BLower cost
  • CA higher melting point
  • DLower brittleness
  • EGreater strength

Which property of bronze made bronze cannons last longer than those made of iron?

  • AGreater corrosion resistance
  • BGreater hardness
  • CLower friction
  • DLower brittleness
  • EGreater strength

Which property of bronze made bronze cannons easier to cast than those made of iron?

  • AA lower melting point
  • BLower density
  • CGreater corrosion resistance
  • DLower cost
  • EGreater malleability

Which property of bronze allowed bronze cannons to fire cannonballs at higher speeds than those made of iron?

  • ALower friction
  • BLower brittleness
  • CGreater density
  • DGreater strength
  • EA higher melting point

Q7:

Alloys of tin and lead are commonly used as electrical solders. Shown in the table is the variation of melting point with the lead content of a solder, as a percentage of the total mass. Note that the lead content of the alloy may be higher than the values shown in the table.

Lead Content (%)05101520253035404550
Melting Point (C)232226220214208202196190193205217

Use a plot of the data in the table to identify which of the following conclusions is most valid.

  • AThe melting point of the solder is negatively correlated with the lead content.
  • BThe melting point of the solder cannot be higher than 232C.
  • CThe melting point of the solder cannot be lower than 190C.
  • DThe melting point of the solder is most strongly affected by lead when the lead content is below 35%.
  • EThe melting point of the solder reaches a minimum at a lead content between 35% and 40%.

Use a plot of the data in the table to determine, to the nearest degree, the melting temperature of a solder with a lead content of 22.5%.

Use a plot of the data in the table to determine, to the nearest percentage unit, the minimum lead content of a solder that can be melted by a 200C electric heater.

Use a plot of the data to estimate, to the nearest 10C, the melting point of pure lead.

Q8:

Metals X and Y can be combined in any ratio to produce an alloy of varying strength. Shown in the graph are the accurately measured strengths of alloys containing different amounts of X and Y. For each alloy, the X content is recorded as a percentage of the total alloy mass.

To the nearest percentage unit, what is the X content when the strength of the alloy reaches its maximum measured value?

Which of the following statements best describes the variation in strength when the X content increases from 5% to 10%?

  • AAlloys become more difficult to roll into sheets.
  • BAlloys become more difficult to scratch.
  • CAlloys become more resistant to stretching and compression.
  • DAlloys break less easily when stretched.
  • EAlloys crack less easily under impact.

A student states that there is a positive correlation between the X content and alloy strength when the X content is less than 15%. Identify the main problem with this conclusion.

  • AStrength does not always increase with X content when the X content is low.
  • BStrength does not always increase with X content when the X content is high.
  • CThe graph does not span all values of X content above 15%.
  • DThe graph does not span all values of X content below 15%.
  • EAdding X only weakly affects strength when the X content is close to 15%.

A student states that the alloys have a minimum strength of 95 MPa. Identify the main problem with this conclusion.

  • AAlloys with X contents lower than the measured values could be weaker.
  • BAlloys with X contents between the measured values could be weaker.
  • CThe lowest measured strength is greater than 95 MPa.
  • DAlloys with X contents greater than the measured values could be weaker.
  • EThe lowest measured strength is less than 95 MPa.

Q9:

A mechanical bearing is a sleeve of metal placed between the axle and the body of a vehicle to ensure smooth rotation. Bronze and stainless steel are both corrosion resistant, but bronze is a far more effective bearing material. Which physical property of bronze makes it more suitable than stainless steel for this application?

  • ALess thermal expansion
  • BGreater stiffness
  • CLower friction
  • DLess static charge
  • EGreater hardness

Q10:

Bronze is an alloy of copper and .

  • Alead
  • Bzinc
  • Ctin
  • Diron
  • Enickel

Q11:

The properties of two copper alloys are listed in the table.

AlloyAlloying ElementPropertiesColor
AXHard and brittleRed brown
BYStrong and malleableYellow

Identify alloy A.

  • ABrass
  • BBronze
  • CSteel
  • DConstantan
  • EPewter

Identify alloy B.

  • ASteel
  • BPewter
  • CBrass
  • DBronze
  • EConstantan

Identify element X.

  • ANickel
  • BZinc
  • CLead
  • DTin
  • ECarbon

Identify element Y.

  • ANickel
  • BZinc
  • CLead
  • DCarbon
  • ETin

Q12:

A solid alloy is produced by combining small amounts of element A with a metal B. Why might this alloy be described as a solid solution?

  • AAtoms of B increase the electrical conductivity of A, like solutes in a solvent.
  • BAtoms of B disrupt the lattice of A to produce voids that can be occupied by solvents.
  • CAtoms of B can move freely through the lattice of A, like solutes in a solvent.
  • DAtoms of B disrupt the lattice of A to produce a highly disordered structure resembling a solution.
  • EAtoms of B randomly replace atoms in the lattice of A, like solutes in a solvent.

Q13:

Alloys of a particular metal display lower malleability. Which of the following properties is also likely to be lower in these alloys?

  • AMelting point
  • BStrength
  • CDensity
  • DHardness
  • EDuctility

Q14:

Fill in the blank: Brass is an alloy of copper and .

  • Anickel
  • Btin
  • Ciron
  • Dlead
  • Ezinc

Q15:

Aluminum may be alloyed with a wide variety of metals, including copper, magnesium, lithium, and manganese. In a space shuttle, fuel consumption was minimized by the use of aluminum alloys of minimal density. Using the element symbols, arrange the alloying metals listed in order of increasing suitability for this application.

  • ACu, Mn, Mg, Li
  • BCu, Li, Mn, Mg
  • CMn, Cu, Mg, Li
  • DLi, Mg, Cu, Mn
  • EMg, Mn, Li, Cu

Q16:

Jewelry is often produced from alloys of gold with copper and nickel. Which of the following properties is not improved by alloying gold with these metals for jewelry-making?

  • AColor
  • BCost
  • CCorrosion resistance
  • DHardness
  • EStrength

Q17:

Which of the following is the best description of an alloy?

  • AA solid solution of one or more elements within a pure metal
  • BA mixture of two or more non-metals
  • CA pure metal
  • DThe product of smelting
  • EA material made by alternating layers of different materials

Q18:

Fill in the blanks: Brass—a solid solution consisting of zinc and copper atoms—can be considered and .

  • Aa homogeneous alloy, an interstitial alloy
  • Ban intermetallic alloy, an interstitial alloy
  • Ca substitutional alloy, an intermetallic alloy
  • Da substitutional alloy, an interstitial alloy
  • Ea pure metal, an intermetallic alloy

Q19:

Steel, a solid solution consisting of carbon atoms seated in the holes of an iron atom structure, is an example of .

  • Aan alkali metal
  • Ba pure metal
  • Ca substitutional alloy
  • Dan interstitial alloy

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