On The Microstructures and Some Incidental Properties of Al–Cr Alloys Solidified Rapidly

Abstract

The structural change and some incidental properties of Al–Cr alloys (up to 3 wt% Cr) by rapid solidification at cooling rates between 10² and 10³°C/sec were investigated. The results obtained are as follows : (1) It is shown that the supersaturated solid solutions can be formed by rapid solidification and the minimum cooling rate to dissolve solute chromium supersaturatedly in pure aluminium is more than about 600°C/sec for 2 wt% Cr and about 1000°C/sec for 3 wt% Cr, respectively. (2) The microstructures of these solid solutions are composed of the dendrite cell structure of the primarily crystallized α phase and the appearance of CrAl₇, which has to crystallize primarily in an equilibrium condition, is obstructed. (3) The disintegration temperature of the supersaturated solid solutions of Al-2 wt% Cr alloys is 250°∼300°C. (4) Any precipitation hardening cannot be recognized by disintegration of these present metastable solid solutions.