Structure/property observations for AlTiCr alloys near the cubic (Al,Cr) < inf> 3 Ti phase

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The nature of the six phases surrounding the cubic Al3Ti phase has been determined for AlTiCr alloys hot isostatically pressed at 1473 K. The cubic phase itself is stable from 7 to 13 at.%Cr foralloys with the titanium level at the stoichiometric 25 at.% and the field is at least 4 at.% wide in titanium. Hardness profiles for alloys containing 23, 25 and 27 at.% Ti indicate that the off-stoichiometric levels of titanium cause strengthening of the cubic phase, with a minimum in hardness near the tetragonal/cubic solvus at 8 at.% Cr and 25 at.% Ti. Excess titanium causes greater strengthening of the cubic phase than does a deficiency of titanium. Second phases such as Al3Ti, AlCr2 and TiCrAl embrittle the cubic matrix, as does the porosity that forms readily during conventional heat treatment. In general, hot isostatic pressing prevents the formation of porosity and improves the cracking resistance of AlTiCr alloys. © 1992.

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Materials Science and Engineering A