Growth conditions and mechanical properties of metastable Al-Fe regular eutectic alloys

Abstract

Al-1.1 to 4.1%Fe alloys were directionally solidified at solidification rates 30 to 1, 000 μm/sec under temperature gradient 50 to 70°C/cm. Seven ranges of microstructures are classified depending on compositions and solidification rates. A metastable Al-FeAl₆ eutectic grows at the rate above 130, um/sec independing on compositions. A coupled region of Al-FeAl₆ eutectic lies at Fe 2.5 to 3.2%, in which the shape of FeAl₆ changes from ribbon to rod-like with increase of solidification rates. It takes a fine rod-type regular eutectic at the rates above 500 μm/sec. The interphase spacing of FeAl₆ λ and the solidification rate R are : Rλ² = 270 μm³/sec. A rod-type regular eutectic has the maximum strength about 27 kg/mm² two times or more than the strength of Al-FeAl₆ eutectic. The Al-FeAl₆ eutectic also has the strength about two times larger than that of Al-FeAl₃ eutectic at 200° and 300°C. Typical stress-strain curves and fractographs are represented.