A mathematical model to predict the strength of aluminum alloys subjected to precipitation hardening

A number of alloys, notably most of the aluminum alloys, can be heat treate d by aging. This aging due to time-dependent precipitation hardening increa ses the strength and hardness as well as modifying other mechanical propert ies. Precipitation hardening has been a popular strengthening mechanism for many decades; therefore, extensive information is available in literature about the precipitation-hardening response of various series of aluminum al loys. The age-hardening response of these alloys is usually represented in graphical form as plotted between property changes and aging time for diffe rent temperatures. In designing a suitable precipitation-hardening strategy , one can refer to these graphs. However, for automatic control of aging fu rnaces, as well as for decision making regarding optimal selection of aging conditions (time/temperature combination), it is desirable to express thes e relationships in a formal mathematical structure. A mathematical model is developed in this article for widely used heat treatable aluminum alloys u sed in the extrusion industry. This model is a condensed representation of all sigma = f(T, t) curves in different series of aluminum alloys, and the parameters of this model characterize the various compositions of the alloy s in the series.