The Experts below are selected from a list of 1044 Experts worldwide ranked by ideXlab platform

Randall M German - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolution during the supersolidus liquid phase sintering of nickel-based Prealloyed Powder mixtures
    Journal of Materials Science, 2000
    Co-Authors: Ronald G Iacocca, Randall M German
    Abstract:

    A novel concept for full-density sintering is described. Two Prealloyed Powders with slight compositional differences are tailored to separate the solidus temperatures into high-melt and low-melt compositions. A mixture of these two Powder compositions allows full-density sintering at a temperature between the two solidus temperatures. For these experiments, the two Powders were nickel-based alloys, where the low-melt Powder contained boron. The mixed Powders were sintered at temperatures above the solidus of the low-melt Powder to form a transient liquid that promoted rapid densification of the mixture. Microstructure evolution during sintering was assisted using quenching experiments. Variables in this study included the heating rate, peak temperature, hold time, and Powder ratio. Interdiffusion between the two Powders controls microstructure evolution, with a dominant role associated with boron diffusion and reaction. The transient liquid phase responsible for densification is linked to boron diffusion and subsequent compound precipitation.

  • densification during the supersolidus liquid phase sintering of nickel based Prealloyed Powder mixtures
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 1999
    Co-Authors: Anand Lal, Ronald G Iacocca, Randall M German
    Abstract:

    This article examines densification during supersolidus liquid-phase sintering (SLPS) of a mixture of two nickel-based Prealloyed Powders. The two Powders were of similar compositions, where one Powder alloyed with boron had a lower melting-temperature range than the other. Sintering of such binary Powder systems is performed at temperatures above the solidus of the low-melting Powder, to form a liquid phase that promotes densification. Measurements of shrinkage, sintered density, and melting were used to determine the densification mechanism. An increase in the fraction of the high-melting Powder resulted in retardation of sintering. A densification model based on viscous flow was developed using rheological principles. The model is a first step in the extension of the conventional models of densification of single Prealloyed Powders to ones of mixtures of Prealloyed Powders. It incorporates the effects of homogenization between the two Powders, specifically, the diffusion of boron from the low-melting to the high-melting Powder. The densification of the Powder mixture was found to depend on the extent of melting of the low-melting Powder and the fraction of the high-melting Powder.

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

  • comparison of microstructure and mechanical behavior of ti 35nb manufactured by laser Powder bed fusion from elemental Powder mixture and Prealloyed Powder
    Journal of Materials Science & Technology, 2022
    Co-Authors: J C Wang, Yujing Liu, Shunxing Liang, Y S Zhang, Lianbo Wang, T B Sercombe, Laichang Zhang
    Abstract:

    Abstract Although different types of Powder feedstock are used for additive manufacturing via laser Powder bed fusion (L-PBF), limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those Powder feedstock. This work investigated the microstructure, phase composition, melt pool morphology, and mechanical properties of a Prealloyed Ti-35Nb alloy manufactured using L-PBF and compared these to their counterparts produced from elemental Powder mixture. The samples manufactured from the Powder mixture are composed of randomly distributed undissolved Nb in the α/β matrix, resulting from the unstable melt pool during the melting of the Powder mixture. By contrast, parts produced from Prealloyed Powder display a homogeneous microstructure with β and α″ phases, owing to the full melting of Prealloyed Powder, therefore, a more stable melt pool to achieve a homogeneous microstructure. The Ti-35Nb manufactured from Prealloyed Powder exhibits large tensile ductility (about 10 times that of the counterparts using mixed Powder), attributed to the high homogeneity in microstructure and chemical composition, strong interface bonding, relatively low oxygen content, and the existence of a large amount of β phase. This work sheds insights into understanding the effect of Powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts.

Ronald G Iacocca - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolution during the supersolidus liquid phase sintering of nickel-based Prealloyed Powder mixtures
    Journal of Materials Science, 2000
    Co-Authors: Ronald G Iacocca, Randall M German
    Abstract:

    A novel concept for full-density sintering is described. Two Prealloyed Powders with slight compositional differences are tailored to separate the solidus temperatures into high-melt and low-melt compositions. A mixture of these two Powder compositions allows full-density sintering at a temperature between the two solidus temperatures. For these experiments, the two Powders were nickel-based alloys, where the low-melt Powder contained boron. The mixed Powders were sintered at temperatures above the solidus of the low-melt Powder to form a transient liquid that promoted rapid densification of the mixture. Microstructure evolution during sintering was assisted using quenching experiments. Variables in this study included the heating rate, peak temperature, hold time, and Powder ratio. Interdiffusion between the two Powders controls microstructure evolution, with a dominant role associated with boron diffusion and reaction. The transient liquid phase responsible for densification is linked to boron diffusion and subsequent compound precipitation.

  • densification during the supersolidus liquid phase sintering of nickel based Prealloyed Powder mixtures
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 1999
    Co-Authors: Anand Lal, Ronald G Iacocca, Randall M German
    Abstract:

    This article examines densification during supersolidus liquid-phase sintering (SLPS) of a mixture of two nickel-based Prealloyed Powders. The two Powders were of similar compositions, where one Powder alloyed with boron had a lower melting-temperature range than the other. Sintering of such binary Powder systems is performed at temperatures above the solidus of the low-melting Powder, to form a liquid phase that promotes densification. Measurements of shrinkage, sintered density, and melting were used to determine the densification mechanism. An increase in the fraction of the high-melting Powder resulted in retardation of sintering. A densification model based on viscous flow was developed using rheological principles. The model is a first step in the extension of the conventional models of densification of single Prealloyed Powders to ones of mixtures of Prealloyed Powders. It incorporates the effects of homogenization between the two Powders, specifically, the diffusion of boron from the low-melting to the high-melting Powder. The densification of the Powder mixture was found to depend on the extent of melting of the low-melting Powder and the fraction of the high-melting Powder.

Laichang Zhang - One of the best experts on this subject based on the ideXlab platform.

  • comparison of microstructure and mechanical behavior of ti 35nb manufactured by laser Powder bed fusion from elemental Powder mixture and Prealloyed Powder
    Journal of Materials Science & Technology, 2022
    Co-Authors: J C Wang, Yujing Liu, Shunxing Liang, Y S Zhang, Lianbo Wang, T B Sercombe, Laichang Zhang
    Abstract:

    Abstract Although different types of Powder feedstock are used for additive manufacturing via laser Powder bed fusion (L-PBF), limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those Powder feedstock. This work investigated the microstructure, phase composition, melt pool morphology, and mechanical properties of a Prealloyed Ti-35Nb alloy manufactured using L-PBF and compared these to their counterparts produced from elemental Powder mixture. The samples manufactured from the Powder mixture are composed of randomly distributed undissolved Nb in the α/β matrix, resulting from the unstable melt pool during the melting of the Powder mixture. By contrast, parts produced from Prealloyed Powder display a homogeneous microstructure with β and α″ phases, owing to the full melting of Prealloyed Powder, therefore, a more stable melt pool to achieve a homogeneous microstructure. The Ti-35Nb manufactured from Prealloyed Powder exhibits large tensile ductility (about 10 times that of the counterparts using mixed Powder), attributed to the high homogeneity in microstructure and chemical composition, strong interface bonding, relatively low oxygen content, and the existence of a large amount of β phase. This work sheds insights into understanding the effect of Powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts.

Andre Schneider - One of the best experts on this subject based on the ideXlab platform.