Thermal expansion of Al-Cu alloys after conditioning and heat treatment

There is a huge amount of works on the study of the invar effect including alloying of iron-nickel bases by all the available elements of the periodic table, including precious metals ( Pt, Pd ). However, the secret of the invar effect is still not clear. The effect of copper on the linear expansion of commercial purity aluminum A7 was studied previously. The results obtained led to the conclusion that it can be reasonable to use copper to produce light alloys with controlled thermal expansion. The mechanism of the thermal expansion of as-cast and deformed Al-Cu alloys depends on the melt conditioning and heat treatment. The melt conditioning is presented by the water steam purging. It is found that the melt conditioning leads to anomalies, which are reflected in the reduction of thermal expansion of the alloys of interest. Further heat treatment leads to the development of anomalies. It is shown that the hot plastic deformation significantly affect the temperature coefficient of linear expansion (TCLE, α) aluminum-copper alloys and the effect increases with copper content increasing. The possibility of application of the discovered mechanism to create a new invar alloys, differing by a low specific weight and lower cost is investigated.

temperature coefficient of linear expansion, Al-Cu alloys, Invar, melt conditioning, heat treatment, anomaly of TCLE