5. Outlook

The Invar itself is now a well-established product, both in terms of its manufacture and the applications it is intended to serve. This does not mean, however, that all research and improvement has become pointless.

For example, the simple observation already mentioned of the difference in expansion between the work-hardened and annealed states opens up a possible avenue for progress in the quest for ever-lower coefficients of expansion. Indeed, if the application requires an annealed material to exhibit the desired mechanical or magnetic properties, then its coefficient of expansion is not minimal. Conversely, a work-hardened material has the lowest expansion, but loses its formability and magnetic properties.

So how do we solve the dilemma?

The answer is conceptually quite simple: the work-hardened state is characterized...