ABSTRACT
It has been recognized for many years that the mechanical performance of materials is affected by the presence of impurities. Papers dating from the first half of this century consider this problem and suggest that uncontrolled impurities could be detrimental [1-4]. However, during the 1950s and 1960s, as outlined below, concern about the cleanliness of materials became especially great because of the demands of the power generation industry. This interest led to significant research on ways to manufacture clean materials, methods to analyze for impurities, and documentation of the harmful effects of these impurities. This book attempts to summarize this progress and present a picture of where each of these areas of research stands today. The purpose of this introductory chapter is to provide a historical background for this work so that it can be set in the proper perspective.
