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S Guha - One of the best experts on this subject based on the ideXlab platform.

  • comments on the effect of directional Solidification Parameter on the structure and property of ni50al20fe30
    Scripta Materialia, 1996
    Co-Authors: I Baker, S Guha
    Abstract:

    *Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, U.S.A. #MER Corp., 7960 S. Kolb Road, Tucson, AZ 85706, U.S.A. (Received January 4, 1996) In a recent paper Chen et al. (1) discussed the effect of directional Solidification processing at different Solidification rates on the structure and mechanical properties of Ni,,Al,,Fe,,. The purpose of the present short nfote is twofold: first, to clarify the phases present in this alloy at or near equilibrium; and second, to point out that mechanical properties superior to those obtained by Chen et al. (1) for direc- tionally-solidified material have previously been reported for the same alloy. Concerning the phases present, Chen et al. (1) describe Ni,,Al,$e,, processed by directional solidi- fication as consisting of various distributions of a y phase and a p phase. (The crystal structures of y and p were undefined by the authors but we assume that these refer to ordered f.c.c., or Ll,, and ordered b.c.c., or B2, respectively based on their reference to the work by Inoue et a1.(4). We will follow the nomenclature of earlier work and refer to these as y and b’, respectively (2-5) and reserve g and b for the f.c.c. and b.c.c. phases, respectively, which are nearby on the phase diagram (5).) Inoue et a1.(4) rapidly-solidified Ni,,,Al,,Fe,, and described the resulting duplex structure as consisting of grains of p’ and v. In contrast, later work by Field et a1.(2) reported a similar microstructure after rapid solidi- fication but instead being p’ and p, the phases present were p’ and of y containing fine y precipitates. In both cases the microstructures are, of course, non-equilibrium. However, the microstructure of Ni,,Al,,Fe,, processed by casting and hot-extrusion in steel cans, followed by air-cooling was also shown by Guha et al. (2) to consist of p’ and y, with the latter again containing fine y precipitates, see Figure 1. Only after annealing at temperatures of 1100 K or above (followed by water quenching) did Guha et al. (3:) observe that the y/y grains became disordered, i.e. they became simply y. The phases observed by Field et al. (6) and Guha et al. (2,3) are consistent with the reported phase diagram (5). Thus, it appears likely that the microstucture of the directionally-solidified NiSoAlzoFe,, studied by Chen et al. (1) consists of grains of p’ and y/v, and not simply p’ and y (p and y in their nomen- clature) as the:y report. Of course, by using only a scanning electron microscope Chen et al. (1) would be unable to observe this. Figure 2 shows the fracture strain as a function of lamellae width (the average of the reported p’ and y widths) for Chen et al’s (1) alloys and includes a datum Tom Guha et al. (2). The data suggest that for aligned eu.tectic lamellar structures, i.e. ignoring the point for the equiaxed grain structure, the fracture strain broadly increases with decreasing lamellar spacing. In other words, it is not directional Solidification ,that improves ductility (the point from Guha et al. (1991) is for double-extruded mate- rial) but refining the microstructure. Further, one can suggest that producing an aligned microstructure

I Baker - One of the best experts on this subject based on the ideXlab platform.

  • comments on the effect of directional Solidification Parameter on the structure and property of ni50al20fe30
    Scripta Materialia, 1996
    Co-Authors: I Baker, S Guha
    Abstract:

    *Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, U.S.A. #MER Corp., 7960 S. Kolb Road, Tucson, AZ 85706, U.S.A. (Received January 4, 1996) In a recent paper Chen et al. (1) discussed the effect of directional Solidification processing at different Solidification rates on the structure and mechanical properties of Ni,,Al,,Fe,,. The purpose of the present short nfote is twofold: first, to clarify the phases present in this alloy at or near equilibrium; and second, to point out that mechanical properties superior to those obtained by Chen et al. (1) for direc- tionally-solidified material have previously been reported for the same alloy. Concerning the phases present, Chen et al. (1) describe Ni,,Al,$e,, processed by directional solidi- fication as consisting of various distributions of a y phase and a p phase. (The crystal structures of y and p were undefined by the authors but we assume that these refer to ordered f.c.c., or Ll,, and ordered b.c.c., or B2, respectively based on their reference to the work by Inoue et a1.(4). We will follow the nomenclature of earlier work and refer to these as y and b’, respectively (2-5) and reserve g and b for the f.c.c. and b.c.c. phases, respectively, which are nearby on the phase diagram (5).) Inoue et a1.(4) rapidly-solidified Ni,,,Al,,Fe,, and described the resulting duplex structure as consisting of grains of p’ and v. In contrast, later work by Field et a1.(2) reported a similar microstructure after rapid solidi- fication but instead being p’ and p, the phases present were p’ and of y containing fine y precipitates. In both cases the microstructures are, of course, non-equilibrium. However, the microstructure of Ni,,Al,,Fe,, processed by casting and hot-extrusion in steel cans, followed by air-cooling was also shown by Guha et al. (2) to consist of p’ and y, with the latter again containing fine y precipitates, see Figure 1. Only after annealing at temperatures of 1100 K or above (followed by water quenching) did Guha et al. (3:) observe that the y/y grains became disordered, i.e. they became simply y. The phases observed by Field et al. (6) and Guha et al. (2,3) are consistent with the reported phase diagram (5). Thus, it appears likely that the microstucture of the directionally-solidified NiSoAlzoFe,, studied by Chen et al. (1) consists of grains of p’ and y/v, and not simply p’ and y (p and y in their nomen- clature) as the:y report. Of course, by using only a scanning electron microscope Chen et al. (1) would be unable to observe this. Figure 2 shows the fracture strain as a function of lamellae width (the average of the reported p’ and y widths) for Chen et al’s (1) alloys and includes a datum Tom Guha et al. (2). The data suggest that for aligned eu.tectic lamellar structures, i.e. ignoring the point for the equiaxed grain structure, the fracture strain broadly increases with decreasing lamellar spacing. In other words, it is not directional Solidification ,that improves ductility (the point from Guha et al. (1991) is for double-extruded mate- rial) but refining the microstructure. Further, one can suggest that producing an aligned microstructure

Z Q Hu - One of the best experts on this subject based on the ideXlab platform.

Comondore Ravindran - One of the best experts on this subject based on the ideXlab platform.

  • Relationships Between Solidification Parameters in A319 Aluminum Alloy
    Journal of Materials Engineering and Performance, 2018
    Co-Authors: Eli Vandersluis, Comondore Ravindran
    Abstract:

    The design of high-performance materials depends on a comprehensive understanding of the alloy-specific relationships between Solidification and properties. However, the inconsistent use of a particular Solidification Parameter for presenting materials characterization in the literature impedes inter-study comparability and the interpretation of findings. Therefore, there is a need for accurate expressions relating the Solidification Parameters for each alloy. In this study, A319 aluminum alloy castings were produced in a permanent mold with various preheating temperatures in order to control metal cooling. Analysis of the cooling curve for each casting enabled the identification of its liquidus, Al-Si eutectic, and solidus temperatures and times. These values led to the calculation of the primary Solidification rate, total Solidification rate, primary Solidification time, and local Solidification time for each casting, which were related to each other as well as to the average casting SDAS and material hardness. Expressions for each of their correlations have been presented with high coefficients of determination, which will aid in microstructural prediction and casting design.

J Chen - One of the best experts on this subject based on the ideXlab platform.