This book was first published in 1980. A great number of metallic materials in practical use owe their strength to the presence in their microstructure of particles of a hard precipitated phase. The text emphasises the importance of scientific rather than empirical methods in attempting to develop particle-hardened alloys. The author progresses from an elementary knowledge of metallurgy to theories relating to the deformation and fracture of alloys of this type. He also discusses the use of such theories to describe observations on both model materials and practical metals. After a discussion of the microstructures of these alloys, how they form and how to describe them quantitatively, their deformation and fracture behaviour at both low and elevated temperatures are examined.