6. Conclusions

Invar, discovered over a century ago by Charles-Édouard Guillaume, gave rise to a whole family of alloys with controlled expansion and elasticity. This early discovery paved the way for iron-nickel alloys with special properties, which were developed to meet specific applications as their use values were identified and defined. This development was accompanied by a concomitant and constant evolution in manufacturing and processing techniques; the aim was to adjust the properties of use by controlling, for this particular type of material, the basic composition, the nature and content of addition and residual elements, the metallurgical state (through thermomechanical transformations), not forgetting the state of magnetization.

The description of Invar's characteristics presented in this article shows that the field for satisfying the required physical, mechanical...