Techniques Considered General Behavior

Rolled zinc is produced as sheet, strip, plate, rod, and wire in numerous compositions and alloys, depending on the ultimate uses of the rolled products. When desired, strip is slit into narrow widths. Most sheet zinc is now produced in a single casting and rolling operation, replacing the discontinuous pack rolling method used formerly. 

The unalloyed zinc used for roofing up to about the 1960s was soft and had a tendency to creep, with the result that if the bays of fully supported roofing were too wide, they would eventually sag in the middle. 

For the manufacture of cans that form the container and one of the electrodes of the dry cell (the flashlight battery), the battery manufacturers have special requirements for the purity and for small alloying additions, both of which can improve the efficiency of the cell, Historically, the manufacture of photoengraving plates required a very uniform metallurgical structure and lack of directional effects, but the market for these plates has largely vanished. This book also does not cover the deliberate corrosion reactions involved in batteries and photoengraving plates. 

The ZA alloys have better general corrosion resistance than zinc or the zinc-4% aluminum alloys in many environments, while alloying and technological improvements increase the resistance to intergranular attack, which was historically a problem with zinc-4% aluminum castings produced from material in which impurities were inadequately controlled. These advances also allow more tolerance of impurities in specifications. 

Cast alloys must be made from at least 99.99% purity zinc ingot to comply with the standards of the American Society for Testing and Materials (ASTM B6) and the International Organization for Standardization (ISO 752) a standard is in preparation by the Comit Europeen de Normalisation (CEN European Committee for Standardization). The harmful impurities, which occur naturally in zinc or as contaminants in the other alloying ingredients, are lead, tin, cadmium, indium, and thallium. These impurities are limited by specification higher contents than specified may make the alloys susceptible to intergranular corrosion, particularly when exposed to warm, moist environments. 

---

While classical phase diagrams provide a powerful methodology for grasping the thermodynamic behavior of few-component systems, it is evident that the restricted 2D or 3D realm of human graphical intuition cannot adequately cope with the complexities of many-component systems. Hence, it is important to find generalized analytical techniques that can accurately represent many-component phase behavior for arbitrary values of c. Such techniques will be considered in the metric geometric representation of multicomponent phenomena (Chapter 12). 

Since this chapter is focused on electrooptic materials and two-photon absorption, we will not consider measurement techniques for y and y(31 in detail, but refer the interested reader to Ref. [19]. In this section, we will briefly describe some of the techniques that have been used for the measurement of the two-photon cross-section, d. We first recall that the 2PA behavior of a molecule is characterized by a spectrum entirely analogous to a one-photon absorption (1PA) spectrum. Although, from the point of view of an application at a particular wavelength, measurements of d at only that wavelength may contribute to a figure-of-merit for that application, more generally, to understand structure-property relationships, it is helpful to acquire 2 PA data over as wide a frequency range as permitted by the lasers available and by the onset of 1PA. 

---