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Both rare‐earth doping and microgravity solidification processing bring significant influences upon the structure formation and mechanical properties of various alloys. Herein, the microstructure and performance of 13Cr martensitic stainless steel are modulated by adding minor Ce content and microgravity solidification by means of drop tube technique. The lattice structure of constituent phase α(Fe) is deformed evidently by microgravity solidification, and the lattice parameter variation is 1.8 times of that caused by Ce addition. The microstructures of this steel processed by arc melting consist of lath‐shaped martensites and a few feather‐shaped bainites whose volume fraction increases with the Ce content. The bainite is replaced by ferrite in the rapidly solidified microstructure of 13Cr steel under microgravity condition. Although both microgravity solidification and Ce addition induce the microstructure refinement and inclusion spheroidization, the former effect plays the dominant role. The compressive properties and microhardness decrease moderately with Ce addition due to the slight increase in bainite, however, the microgravity solidification brought the hardening effect and thus the microhardness of the steel droplets increases with undercooling. [ABSTRACT FROM AUTHOR]

Under the conventional solidification condition, a liquid aluminium alloy can be hardly undercooled because of oxidation. In this work, rapid solidification of an undercooled liquid Al80.4Cu13,6Si6 ternary eutectic alloy was realized by the glass fluxing method combined with recycled superheating. The relationship between superheating and undercooling was investigated at a certain cooling rate of the alloy melt. The maximum undercooling is 147 K (0.18TE). The undercooled ternary eutectic Is composed of α(Al) solid solution, (Si) semiconductor and O(CuAI2) intermetallic compound. In the (Al+Si+θ) ternary eutectic, (Si) faceted phase grows independently, while (Al) and 0 non-faceted phases grow cooperatively in the lamellar mode. When undercooling is small, only (Al) solid solution forms as the leading phase. Once undercooling exceeds 73 K, (Si) phase nucleates firstly and grows as the primary phase. The alloy microstructure consists of primary (Al) dendrite, (Al+θ) pseudobinary eutectic and (Al+Si+θ) ternary eutectic at small undercooling, while at large undercooling primary (Si) block, (Al+θ) pseudo-binary eutectic and (Al+Si+θ) ternary eutectic coexist. As undercooling increases, the volume fraction of primary (Al) dendrite decreases and that of primary (Si) block increases. [ABSTRACT FROM AUTHOR]

Rapid growth behavior of ζ phase has been investigated in the undercooling experiments of Cu-14%Ge, Cu-15%Ge, Cu-18.5%Ge and Cu-22%Ge alloys. Alloys of the four compositions obtain the maximum undercoolings of 202 K(0.17TL), 245 K(0.20TL), 223 K(0.20TL) and 176 K(0.17TL), respectively. As the content of Ge increases, the microstructural transition of "α(Cu) dendrite + ζ peritectic phase → peritectic phase → ζdendrite + (ϵ+ζ) eutectic" takes place in the alloy at small undercooling, while the microstructural transition of fragmented α(Cu) dendrite + ζ peritectic phase → ζ peritectic phase → ζ dendrite + ϵ phase" happens in the alloy at large undercooling. EDS analysis of the Ge content in ζ peritectic phase indicates that undercooling enlarges the solid solubility of αdendrite, which leads to a decrease in the Ge content in ζ phase as undercooling increases. In the Cu-18.5%Ge alloy composed of ζ peritectic phase, the Ge content in ζ phase increases when undercooling increases, which is due to the restraint of the Ge enrichment on the grain boundaries by high undercooling effect. [ABSTRACT FROM AUTHOR]

Droplets of Ag60Sb34Cu6 ternary alloy within the diameter range of 60–800 μm were rapidly solidified by means of drop tube containerless processing, and the solidification mechanism is analyzed. With a decrease in droplet size, the cooling rate increases from 57 to 5.8×10 K/s. The maximum undercooling is determined to be 180 K (0.23TL) and the microstructure of primary ε(Ag3Sb) dendrite refines drastically until homogenous equiaxed dendrite forms. Experimental results indicate that (ε+Ag) pseudobinary eutectic cannot form under high undercooling conditions and the solubility of Ag in primary ε phase increases as undercooling increases. Based on thermal analysis and crystal growth morphology, it is found that this alloy is solidified in two ways corresponding to different undercooling levels. [ABSTRACT FROM AUTHOR]

Supersaturated Ni–Sn solid solutions with Sn solubility up to 9.2 at% have been obtained through rapid solidification in the undercooling range of 220–280 K. The lattice properties including the lattice constant, microscopic lattice distortion, thermal expansion and linear expansion coefficient are investigated experimentally and theoretically. The lattice constants increase about 0.01 Å per 1 at% Sn in linear way. The lattice distortions are mainly confined to the first nearest-neighbor atoms with the values of (3.5±0.3)%, and are less than 1% for farther atoms. The thermal expansions vary only a little with Sn content and exhibit obvious increase for the as-cast solid solutions above 1150 K due to the phase transformation of Ni 3 Sn compound, whereas they increase smoothly with temperature for the annealed supersaturated samples. [ABSTRACT FROM AUTHOR]