This chapter describes the causes of cracking, embrittlement, and low toughness in carbon and low-alloy steels and their differentiating fracture surface characteristics. It discusses the interrelated effects of composition, processing, and microstructure and contributing factors such as hot shortness associated with copper and overheating and burning as occur during forging. It addresses various types of embrittlement, including quench embrittlement, tempered-martensite embrittlement, liquid-metal-induced embrittlement, and hydrogen embrittlement, and concludes with a discussion on high-temperature hydrogen attack and its effect on strength and ductility.

This chapter reviews the causes and cases associated with the problems originated by tempering of steels. To provide background on this phenomenon, a brief description of the martensite reactions and the steel heat treatment of tempering is given to review the different stages of microstructural transformation. A section describing the types of embrittlement from tempering, along with mechanical tests for the determination of temper embrittlement (TE), is presented. Various factors involved in the interaction of the TE phenomenon with hydrogen embrittlement and liquid-metal embrittlement are also provided. The cases covered are grinding cracks on steel cam shaft and transgranular and intergranular crack path in commercial steels.

Liquid metals are frequently used as a heat-transfer medium because of their high thermal conductivities and low vapor pressures. Containment materials used in such heat-transfer systems are subject to molten metal corrosion as well as other problems. This chapter reviews the corrosion behavior of alloys in molten aluminum, zinc, lead, lithium, sodium, magnesium, mercury, cadmium, tin, antimony, and bismuth. It also discusses the problem of liquid metal embrittlement, explaining how it is caused by low-melting-point metals during brazing, welding, and heat treating operations.

Environmentally assisted cracking is a generic term that includes various cracking phenomena such as stress-corrosion cracking (SCC), corrosion fatigue cracking, and liquid-metal embrittlement. This chapter describes these cracking mechanisms beginning with SCC and the factors that influence its formation. It covers alloy selection and mitigation techniques and includes examples of SCC in aircraft components. The chapter also addresses corrosion fatigue, explaining how different environments and operating conditions affect crack propagation, fatigue strength, and fatigue life. It includes information on liquid-metal embrittlement as well.