Search Results for Liquid metals

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.

Although zirconium resists stress-corrosion cracking (SCC) where many alloys fail, it is susceptible in Fe3+- and Cu2+-containing solutions, concentrated HNO3, halogen vapors, mercury, cesium, and CH3OH + halides. This chapter explains how composition, texture, stress levels, and strain rate affect the SCC behavior of zirconium and its alloys. It describes environments known to induce SCC, including aqueous solutions, organic liquids, hot and fused salts, and liquid metals. It also discusses cracking mechanisms and SCC prevention and control techniques.

This chapter discusses the advantages and disadvantages of metal matrix composites and the methods used to produce them. It begins with a review of the composition and properties of aluminum matrix composites. It then describes discontinuous composite processing methods, including stir and slurry casting, liquid metal infiltration, spray deposition, powder metallurgy, extrusion, hot rolling, and forging. The chapter also provides information on continuous-fiber aluminum and titanium composites as well as particle-reinforced titanium and fiber metal (glass aluminum) laminates.

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.

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.

Titanium and its alloys are used chiefly for their high strength-to-weight ratio, but they also have excellent corrosion resistance, better even than stainless steels. Titanium, as the chapter explains, is protected by a tenacious oxide film that forms rapidly on exposed surfaces. The chapter discusses the factors that influence the growth and quality of this naturally passivating film, particularly the role of oxidizing and inhibiting species, temperature, and alloying elements. It also discusses the effect of different corrosion processes and environments as well as hydrogen, stress-corrosion cracking, liquid metal embrittlement, and surface treatments.

Titanium alloys are generally resistant to stress-corrosion cracking (SCC), but under certain conditions, the potential for problems exists. This chapter identifies the types of service environments where titanium alloys have exhibited signs of SCC. It begins by describing the nominal composition, designation, and grade of nearly two dozen commercial titanium alloys and the different types of media (including oxidizers, organic compounds, hot salt, and liquid metal) in which SCC has been observed. It discusses the mechanical and metallurgical factors that influence SCC behavior and examines the cracking and fracture mechanisms that appear to be involved. The chapter also includes information on SCC test standards and provides detailed guidelines on how to prevent or mitigate the effects of SCC.

The solidification process has a major influence on the microstructure and mechanical properties of metal casting as well as wrought products. This appendix covers the fundamentals of solidification. It discusses the formation of solidification structures, the characteristics of planar, cellular, and dendritic growth, the basic freezing sequence for an alloy casting, and the variations in cooling rate, heat flow, and grain morphology in different areas of the mold. It also describes the types of segregation that occur during freezing, the effect of solidification rate on secondary dendrite arm spacing, and the factors that contribute to porosity and shrinkage.

Almost all metals and alloys are produced from liquids by solidification. For both castings and wrought products, the solidification process has a major influence on both the microstructure and mechanical properties of the final product. This chapter discusses the three zones that a metal cast into a mold can have: a chill zone, a zone containing columnar grains, and a center-equiaxed grain zone. Since the way in which alloys partition on freezing, it follows that all castings are segregated to different categories. The different types of segregation discussed include normal, gravity, micro, and inverse. The chapter also provides information on grain refinement and secondary dendrite arm spacing and porosity and shrinkage in castings. It concludes with a brief overview of six of the most important casting processes in industries: sand casting, plaster mold casting, evaporative pattern casting, investment casting, permanent mold casting, and die casting.

Engineering metals undergo many transformations in the course of production, none more critical than those that occur during solidification. This chapter discusses the process of solidification and its effects on the structure and properties of cast metals. It describes the relationship between cooling rate, grain size, grain shape, and phase structures. It explains how the transition from liquid to solid state creates the conditions under which microsegregation occurs, and how it impacts the distribution of alloying elements, carbides, and inclusions. The link between solidification and porosity is also discussed along with its detrimental effect on the mechanical properties of metal castings.