The influence of the alloy purity level on the properties of Ti–48Al was studied using two sets of samples. The main difference in composition between them was the oxygen concentration, 15 and 980 wt ppm, respectively. The characteristic mechanical values at room temperature, Vickers microhardness, proofstress in compression and creep behaviour at 1073 K were studied for the two sets and for two different microstructures, lamellar microstructure (fully transformed) and duplex microstructure. For the purity levels under study, the oxygen concentration did not influence the microstructure or the room temperature mechanical properties. The creep tests at 1073 K showed that the steady-state strain rate of the pure lamellar alloy was an order of magnitude larger than that of the impure lamellar alloy. In the case of the duplex microstructure, the impurity effect was much less important. The creep strength of the impure lamellar alloy was greater than that of the duplex alloy.
L'influence de la purete sur les proprietes de l'alliage Ti–48Al a ete etudiee en utilisant deux types d'echantillons. La principale difference de composition entre les deux lots d'echantillons residait dans la concentration en oxygene, 15 ppm-poids and 980 ppm-poids respectivement. Les caracteristiques mecaniques a la temperature ambiante, microdurete Vickers, limite elastique en compression, et le comportement en fluage a 1073 K, ont ete etudies pour les deux lots d'echantillons et pour deux microstructures differentes, la microstructure lamellaire (completement transformee) et la microstructure mixte. Aux niveaux de purete consideres, la concentration en oxygene n'avait pas d'influence sur la microstructure et sur les proprietes mecaniques a la temperature ambiante. Les essais de fluage a 1073 K ont montre que la vitesse de fluage en regime stationnaire, dans le cas de la structure lamellaire, etait dix fois plus grande pour l'alliage pur que pour l'alliage impur. Dans le cas de la microstructure mixte, l'effet de la purete etait beaucoup moins important. La resistance au fluage de l'alliage impur etait plus grande dans la structure lamellaire que dans la structure mixte.
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