  The mechanical properties of layered, hexagonal-structured MAX phases often
show the combined merits of metals and ceramics, making them promising material
candidates for safety critical applications. While their unique mechanical
performance largely arises from the crystal structure, the effect of chemistry
on the properties of these materials remains unclear. To study this, here we
employed two in situ electron microscope small scale testing approaches to
examine the micromechanical properties of Zr3AlC2, and compared the results
with the properties of Ti3SiC2: we used micropillar compression tests to
measure basal slip strength, and double cantilever beam splitting tests to
evaluate fracture energy for basal plane delamination. We observed distinct and
systematic differences in these measured properties between Zr3AlC2 and
Ti3SiC2, where Zr3AlC2 appeared to be stronger but more brittle at the
microscale, and discussed the implications of the results in the selection,
design, and engineering of MAX phases for targeted engineering applications.
