[en] Mechanical properties were related to composition and condition for Cr alloys strengthened with TaC, TaB, and TaC + TaB. A 0.25 to 1.00 mole percent alloying range was investigated. Thermomechanical condition had a similar influence on high-temperature strength of the three alloy types. Tensile strengths were highest for heavily warm worked material. Maximum rupture strengths were obtained in the solution treated and aged condition. Composition and alloy content had major influences on rupture properties. Rupture strength was greatly improved by using the alloying phases together as opposed to individually, and a possible synergistic effect was measured. A strong direct relationship between alloy content and the stress dependency of rupture life was observed. Some improvement in low-temperature ductility was obtained by heat treatment and an increase of alloy content, but the lowest ductile-to-brittle transition temperature measured was 300⁰F. Precipitation of the strengthening phases in Cr was also evaluated from electron microscopy and crystallographic data. A (100) habit was identified for the carbide and postulated for the boride. (U.S.)