Book excerpt: Superalloys form a class of the structural materials for high-temperature applications. Nickel superalloys are extensively used in the high-temperature components of gas turbines due to their excellent creep, fatigue, and corrosion resistance at elevated temperatures. These materials are considered paramagnetic in the range of working temperatures. This book presents the features of the ternary phase diagrams Ni-Al-X (X = {Co, Fe, Nb, Ti, Cr}), effects of the alloying on the long-range order and mechanical properties of the Ni3 Al-based alloys. Description of the strain-induced ferromagnetism in the Ni3Al-based alloys and magnetic control of the failure of gas turbine blades are also included. A separate section is devoted to the analysis of the vibration process and strength change in the single-crystal gas turbine blades. This book includes the review of the new intermetallic cobalt superalloys. The structure, crystal lattice parameters, orientation relationships between phases, mechanical and magnetic properties of the Co3(Al,W)-based alloys are described. Non-destructive magnetic point control of the martensite content in low-magnetic austenitic alloys is a new method for detection of the local sites with internal stresses. This method is useful for the detection of the residual stress in the critical parts of industrial products. This book may be useful for specialists in material science, first-year postgraduate students taking a class in material science and engineering, and engineers developing new alloys for the gas turbine technology.