18 Economic and Environmental Considerations Materials scientists often need to advise other engineers who work in different and more specialized areas as to the best suit- ability of certain materials for specific applications.An airplane for example,requires light-weight and high-strength materials such as aluminum or titanium alloys,whereas rotor blades for turbine engines,which have to withstand extremely high tem- peratures,are better served by certain nickel alloys.However, cost,availability,safety,aesthetic appearance,and recyclability of materials likewise need substantial consideration.The latter issues shall be discussed in the present chapter. 18.1。Price Figure 18.1 depicts the price per unit weight of some typical in- dustrial materials between 1900 and 2000.It is observed in this graph that the expense for aluminum decreased in the first half of this century,mostly due to more efficient production tech- niques but also because domestic producers held the price for aluminum at a low steady level to improve their competitive edge against copper in the electrical industry.It can be further seen that,among the materials displayed in Figure 18.1,steel is still the least expensive one if one considers the price on a weight ba- sis.The relative price increases during the past 50 years are es- sentially alike for all depicted substances.Long-term changes in price are caused by increases in cost of labor,energy,trans-18 Materials scientists often need to advise other engineers who work in different and more specialized areas as to the best suit￾ability of certain materials for specific applications. An airplane, for example, requires light-weight and high-strength materials such as aluminum or titanium alloys, whereas rotor blades for turbine engines, which have to withstand extremely high tem￾peratures, are better served by certain nickel alloys. However, cost, availability, safety, aesthetic appearance, and recyclability of materials likewise need substantial consideration. The latter issues shall be discussed in the present chapter. Figure 18.1 depicts the price per unit weight of some typical in￾dustrial materials between 1900 and 2000. It is observed in this graph that the expense for aluminum decreased in the first half of this century, mostly due to more efficient production tech￾niques but also because domestic producers held the price for aluminum at a low steady level to improve their competitive edge against copper in the electrical industry. It can be further seen that, among the materials displayed in Figure 18.1, steel is still the least expensive one if one considers the price on a weight ba￾sis. The relative price increases during the past 50 years are es￾sentially alike for all depicted substances. Long-term changes in price are caused by increases in cost of labor, energy, trans￾Economic and Environmental Considerations 18.1 • Price