Structure and precipitation strengthening in a high-temperature Fe–Ni alloy
Wybrane pełne teksty z tego czasopisma
Purpose: The relationships between the kinetics of precipitation and growth of the intermetallic phase ϒ' [Ni3(Al,Ti)] and the strengthening magnitude obtained in a high-temperature Fe–Ni alloy of the A-286 type has been studied. In order to accomplish the goal of the study, the author used the LSW coagulation theory and Brown and Ham's conventional analysis of strengthening by ordered particles. Design/methodology/approach: The samples were subjected to a solution heat treatment at 980 °C/2h/water and then aged at 715, 750, and 780 °C, with holding times 0.5-500h. The heat-treated samples were subjected to structural analyses (TEM, X-ray diffraction) and analyses of mechanical properties (hardness test, static tensile test, and impact test). Findings: Direct measurements on the electron micrographs allowed to calculate the structural parameters of the ϒ' phase, i.e. mean diameter, volume fraction and mean distance between particles. In accordance with the LSW theory, linear dependencies of changes in mean diameter as a function of aging time (t1/3) were elaborated. The author carried out analyses of strengthening and flow stress (Δ ζ) increases as a function of the particle size of the ϒ' phase and determined the value of the antiphase boundary energy (ϒ APB) for the analyzed Fe–Ni alloy. Practical implications: The obtained relationships of the growth of the ϒ' phase particles as a function of temperature and aging time can be used to determine the magnitude of strengthening and flow stress in hightemperature Fe–Ni alloys during extended aging or usage. Originality/value: This study exploits LSW coagulation theory and Brown and Ham's conventional analysis to describe precipitation strengthening by ordered particles of the intermetallic phase ϒ' in a high temperature Fe–Ni alloy.
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