Abstract
Liquid ternary Fe60Co20Cu20 alloy was undercooled by up to 357 K (0.21 TL) with glass fluxing method and its rapidly solidified microstructures were investigated by EDS and EBSD technologies. The ternary Fe60Co20Cu20 alloy rapidly solidifies with rapid dendritic growth of the primary γ-Fe phase within 37–243 K undercooling range. When the alloy melt is undercooled to 243 K, an obvious phase separation takes place and the uniform alloy melt separates into (Fe, Co)-rich and Cu-rich phases within 243–357 K undercooling range. The primary γ-Fe phase takes place in a solid-state phase transformation and becomes α-Fe phase in the final microstructure. The microstructure of α-Fe phase transforms from coarse dendrite at small undercoolings to equiaxed grain at large undercoolings. EBSD analysis reveals that the coarse α-Fe dendrites grows anisotropically with a leftlangle {110} rightrangle preferred orientation on condition that undercooling is less than 178 K, whereas no apparent preferred growth orientation is found in the equiaxed grains once undercooling exceeds this critical value. The growth velocity of primary γ-Fe dendrite increases up to 37 ms−1 as undercooling increases to 243 K, but it decreases as undercooling further increases, ascribing to that the dendrite growth is impeded by phase separation.
Highlights
Dendritic growth has received a great deal of attention from the materials and physics scientists for centuries [1,2,3,4,5,6,7,8,9,10,11]
We studied the dendritic growth and phase separation under different undercooling conditions for the ternary Fe60Co20Cu20 alloy using the glass fluxing method
The selected alloy composition point was marked in ternary Fe–Co–Cu phase diagram [21, 24, 25]. To map this composition point to three corresponding binary phase diagrams, we can find that the highly undercooled Fe60Co20Cu20 alloy is involved in the metastable immiscible gap of both Fe–Cu and Co–Cu binary alloys
Summary
Dendritic growth has received a great deal of attention from the materials and physics scientists for centuries [1,2,3,4,5,6,7,8,9,10,11]. Over the past few decades, a number of investigators have successfully developed theories to predict the dendritic growth velocity of pure metals and alloys as a function of undercooling [12,13,14,15,16,17]. As a very important parameter for the solidification theory investigation, the dendritic growth velocity (V) under different undercooling (ΔT) conditions has been investigated experimentally and theoretically in the field of materials science. The glass fluxing method [7] and some levitation techniques are usually used to experimentally measure the dendritic growth velocity up to now [2, 15,16,17,18,19]. The dendritic growth velocity in different alloy systems shows good agreement with theoretical model
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