Indexed by:期刊论文
Date of Publication:2022-06-29
Journal:金属学报
Affiliation of Author(s):材料科学与工程学院
Volume:54
Issue:05
Page Number:809-823
ISSN No.:0412-1961
Abstract:Intermetallic compounds (including quasicrystals) have been widely employed as reinforced phases in many alloys due to their high strength, high hardness and good thermal stability. The growth behavior and growth pattern of these intermetallic compounds affect the mechanical properties of materials significantly. However, the intermetallic compound, which exhibits complex crystal structures and directional bonding usually shows a faceted growth pattern with strong anisotropy and forms crystals with a wide range of morphologies and coarse grains during solidification. The inappropriate morphology and size of the intermetallic compound will destroy the integrity of the matrix and thus deteriorate the mechanical properties of materials. In this work, the microstructural evolution, morphology evolution of intermetallic compounds and mechanical properties have been investigated in directionally solidified Al-3Mn-7Be (atomic fraction, %) alloy with a wide pulling rates of 1 similar to 1500 mu m/s. The addition of Be results in the shift of Al-Mn binary phase diagram toward the Mn-rich side, the appearance of intermetallic compounds, namely alpha-phase, T-phase, Be4AlMn, and icosahedral quasicrystal (I-phase) and significantly refines the microstructures of the as-cast and directionally solidified samples. With increasing pulling rates, a transition of primary phase is observed from alpha-phase to T-phase, and then I-phase, accompanied by the formation of the primary Be4AlMn phase, which can be attributed to the increase of supersaturation and supercooling near the solid/liquid interface. Meanwhile, the morphology, size and growth pattern of primary phases vary with the increase of pulling rates. The mechanical properties of directionally solidified Al-3Mn-7Be alloy have been investigated. It is indicated that the room-temperature strength of this alloy decreases first and then increases as the pulling rates increase, and a larger elongation is presented at the lowest and highest pulling rates, which can be attributed to the microstructures of alloys, properties of strengthening phases and the interfaces between matrix and strengthening phase.
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