Materials Homework 6

What features might limit the mechanical uses and applications of aluminum and aluminum alloys?

Aluminum alloys are inferior to steel in the area of elastic modulus. In addition, the wear, creep, and fatigue properties are generally rather poor. In addition, aluminum loses a significant portion of its strength when heated to temperatures much above 350F.

What are some of the attractive engineering properties of aluminum and aluminum alloys?

Aluminum and its alloys have achieved popularity due to their light weight, high electrical and thermal conductivity, good corrosion resistance, workability, variety of available finishes, and recyclability.

What are some of the primary application areas for titanium and titanium alloys?

Application areas: Aerospace, Medical implants, High performance sporting equipment, Heat exchanger etc.

What is the dominant product for which lead is used?

Lead acid battery

What conditions favor the selection and use of nickel-base alloys?

Nickel alloys are noted for their high strength and corrosion resistance, particularly at elevated temperature.

What metals or combinations of metals form the bases of the superalloys?

Nickel, iron and cobalt forms the base metal for the superalloys.

What types of properties do nonferrous metals possess that might not be available in the ferrous metals?

Nonferrous metals often possess certain properties not usually associated with ferrous metals, among them being: corrosion resistance, ease of fabrication, high electrical and thermal conductivity, light weight, strength at elevated temperatures and color.

What are some attractive engineering properties of copper-nickel alloys?

The copper-nickel alloys are particularly well known far their high thermal conductivity and high-temperature strength, coupled with good corrosion resistance.

What are some of the attractive engineering properties that account for the wide use of the copper-zinc brasses?

The copper-zinc alpha brasses are quite ductile and formable, achieve good strength through cold working and have good corrosion resistance and high electrical and thermal conductivities. Both strength and ductility increase with zinc content up to about 36% zinc. In addition, variations in chemistry can be used to produce changes in color and various platings are easy to apply.

What are some attractive and restrictive properties of magnesium and magnesium alloys?

The most attractive property of magnesium is its light weight and companion good strength-to-weight ratio. Unfortunately, magnesium and magnesium alloys can also be characterized by poor wear, creep, fatigue, and corrosion resistance properties when in galvanic couples. The modulus of elasticity is low and the alloys possesses limited ductility.

For what respects are the nonferrous metals generally inferior to steel?

The nonferrous alloys are generally inferior to steel in terms of strength and elastic modulus, and possibly weldability.

What is the primary application of pure zinc? Of the zinc-based engineering alloys?

The primary application of pure zinc is the galvanizing of iron and steel. The principal use of the zinc-based alloys is in die-casting operations. They are low in cost, have low melting points, do not affect steel dies adversely, and can possess good strength and dimensional stability.

What is the primary benefit of aluminum recycling compared to making new aluminum from ore?

The recycling of aluminum saves 95% of the energy required to process aluminum from ore.

Which metals are classified as refractory metals?

The refractory metals consist of: niobium, molybdenum, tantalum, rhenium and tungsten.

What properties make copper attractive for cold-working processes?

The relatively low strength and high ductility make copper quite attractive for forming operations. By cold-working, the tensile strength can be raised from about 30,000 psi to over 65,000 psi., with a concurrent drop in elongation from 60% to about 5%. The low recrystallization temperature is attractive when additional cold working is desired.

What unique property of graphite makes it attractive for elevated-temperature applications?

The strength of graphite increases with the increase in temperature.

What are the three properties of copper and copper alloys that account for many of their uses and applications?

The wide use of copper and copper alloys is largely due to the high electrical and thermal conductivity, high ductility, and corrosion resistance.

What are some of the attractive engineering properties of titanium and titanium alloys? Limiting characteristics?

Titanium and its alloys are strong, lightweight, corrosion resistant, and offer strengths similar to steel at temperatures up to 900F. The limitation of Titanium being very expensive.

What temperature is generally considered to be the upper limit for which titanium alloys retain their useful engineering properties? The superalloy? Refractory Metals?

Titanium is generally considered to have useful engineering properties up to about 900F; superalloys to an in excess of 2000F, and refractory metals up to about 3000F (a temperature that is set by the availability of effective ceramic coatings).

Under what conditions might titanium replace steel? Replace aluminum?

Titanium may replace steel for its light weight and ability to operate at high temperature. The titanium may replace aluminum for its strength and ability to operate at high temperature.

What features make aluminum attractive for transportation applications?

While the obvious attractiveness of aluminum for transportation applications is due to its light weight, additional benefits come from its corrosion resistance, low maintenance expense, and relative ease of fabrication.