A word that means that when two elements are mixed they become stronger

Solution 1:

This is exactly the concept of synergy, and it brings to mind the famous related quotation

"The whole is greater than the sum of its parts."

By the way, this quote is often attributed to Aristotle's Metaphysics. However, there is a claim that "there is no place in Metaphysics where the phrase or anything similar can be found!".

Likewise, others attribute the quote to the Gestalt school of psychology -- although this too is an error, arising from a mistranslation.

Solution 2:

Consider alloy

a metal made by combining two or more metallic elements, especially to give greater strength or resistance to corrosion:

Solution 3:

After having found the following title in The Washington Post, "Marriage Is Greater Than the Sum of Its Parts" by William Raspberry, I think that "marriage", in a metaphorical sense, can be the word you are looking for.

Solution 4:

You could also try one of

The compound effect of A and B ...

or

The synergistic effect of A and B ...

or

The combined effect of A and B ...

Solution 5:

How about "gestalt"? Means pretty much the same as "synergy" (the whole is greater than the sum of its parts) but less likely to have your colleagues ticking jargon bingo boxes.