One of the important considerations when selecting a material for an application is to determine the highest and lowest operating temperature along with the companion properties that must be present at each extreme. The ductile-to-brittle transition temperature, discussed in Section 2-4, has been an important factor in a number of failures. An article that summarized the features of 56 catastrophic brittle fractures that made headline news between 1888 and 1956 noted that low temperatures were present in nearly every case. The water temperature at the time of the sinking of the Titanic was - 2°C, above the freezing point for salt water, but below the transition point for the steel used in construction of the hull of the ship.
a. Which of the common engineering materials exhibits a ductile-to-brittle transition?
b. For plain carbon and low-alloy steels, what is a typical value (or range of values) for the transition temperature?
c. What type of material would you recommend for construction of a small vessel to transport liquid nitrogen within a building or laboratory?
d. Figure 2P-1 summarizes the results of impact testing performed on hull plate from the RMS Titanic and similar material produced for modern steel-hulled ships. Why should there be a difference between specimens cut longitudinally (along the rolling direction) and transversely (across the rolling direction)? What advances in steel making have led to the significant improvement in low-temperature impact properties?

350 Longitudinal 300 5 250 200 150 Modern hull plate Transverse Longitudinal 100 RMS Titanic plate 50 Transverse -100 50 50 100 150 200 Test temperature C) FIGURE 2P-1 Longitudinal and transverse notch toughness data: steel from the RMS Titanic versus modern steel plate. (Courtesy i&SM, Sept. 1999, p. 33 Iron and Steel Society, Warrendale, PA.)