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Journal ArticleDOI

Hot working characteristics of powder metallurgy Nimonic AP-1 superalloy

01 Mar 2001-Powder Metallurgy (Taylor & Francis)-Vol. 44, Iss: 3, pp 267-273
TL;DR: In this article, a simple instability condition based on the Ziegler's continuum principles is extended for delineating the regions of unstable metal flow during hot deformation of Nimonic AP-1 superalloy.
Abstract: A simple instability condition based on the Ziegler's continuum principles as applied to large plastic flow, is extended for delineating the regions of unstable metal flow during hot deformation of Nimonic AP-1 superalloy. The optimum hot working conditions for this material are suggested.
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Journal ArticleDOI
TL;DR: In this paper, a multicomponent Co 20 Cu 20 Fe 20 Ni 20 Ti 20 eutectic high entropy alloy (HEA), processed by vacuum arc melting cum suction casting technique was studied.
Abstract: Multicomponent Co 20 Cu 20 Fe 20 Ni 20 Ti 20 eutectic high entropy alloy (HEA), processed by vacuum arc melting cum suction casting technique was studied. The microstructure of this eutectic HEA consists bcc (β) and fcc (α 2 ) solid solution dendritic phases and eutectics (fcc (α 1 ) plus Ti 2 (Ni, Co)-type Laves phase). Serrations in the flow behaviour are attributed to multi substitutional solutes in the multi-phase microstructure. Based on the detailed analysis of mechanical data together with deformed microstructural characterization, the optimum thermo-mechanical processing conditions for hot working are identified as T=930–990 °C (1203–1263 K) and strain rate range of 10 −3 s −1 –10 −1 s −1 .

90 citations

Journal ArticleDOI
TL;DR: In this article, hot isothermal compression tests were conducted on Cobalt-based superalloy Co 20Cr 15W 10Ni using a thermo-mechanical simulator to study the hot workability and microstructure evolution over a wide range of temperatures and strain rates.

34 citations

Journal ArticleDOI
TL;DR: In this article, a simple instability condition based on Ziegler's continuum principles is extended to define the deformation processing maps that delineate'safe' and 'non-safe' hot working conditions.
Abstract: A simple instability condition based on Ziegler's continuum principles as applied to large plastic flow is extended to define the deformation processing maps that delineate 'safe' and 'non-safe' hot working conditions. Processing maps were developed utilising the measured flow stress data of nickel based powder metallurgy superalloys in a constitutive equation. The applicability of the processing maps developed has been examined by comparing with the reported microstructural observations of deformed compression specimens. Optimum hot working conditions for the materials are suggested, based on the maximum values of the strain rate sensitivity index.

2 citations

References
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Book
01 Oct 1982
TL;DR: Deformation-mechanism maps: the plasticity and creep of metals and ceramics as discussed by the authors, Deformation-Mechanism Maps of metal deformation: the deformation and the creep of metal and ceramic.
Abstract: Deformation-mechanism maps: the plasticity and creep of metals and ceramics , Deformation-mechanism maps: the plasticity and creep of metals and ceramics , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

2,342 citations

Journal ArticleDOI
TL;DR: In this article, a new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented, which considers the workpiece as a dissipator of power in the total processing system and evaluates the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ).
Abstract: A new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented. The approach in this method is to consider the workpiece as a dissipator of power in the total processing system and to evaluate the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ). The optimum processing conditions of temperature and strain rate are those corresponding to the maximum or peak inJ. It is shown thatJ is related to the strain-rate sensitivity (m) of the material and reaches a maximum value(J max) whenm = 1. The efficiency of the power dissipation(J/J max) through metallurgical processes is shown to be an index of the dynamic behavior of the material and is useful in obtaining a unique combination of temperature and strain rate for processing and also in delineating the regions of internal fracture. In this method of modeling, noa priori knowledge or evaluation of the atomistic mechanisms is required, and the method is effective even when more than one dissipation process occurs, which is particularly advantageous in the hot processing of commercial alloys having complex microstructures. This method has been applied to modeling of the behavior of Ti-6242 during hot forging. The behavior of α+ β andβ preform microstructures has been exam-ined, and the results show that the optimum condition for hot forging of these preforms is obtained at 927 °C (1200 K) and a strain rate of 1CT•3 s•1. Variations in the efficiency of dissipation with temperature and strain rate are correlated with the dynamic microstructural changes occurring in the material.

1,121 citations

Book
01 Jan 1963

1,040 citations

Journal ArticleDOI
01 Sep 1978-Science
TL;DR: It is shown that nonequilibrium may become a source of order and that irreversible processes may lead to a new type of dynamic states of matter called "dissipative structures" and the thermodynamic theory of such structures is outlined.
Abstract: Fundamental conceptual problems that arise from the macroscopic and microscopic aspects of the second law of thermodynamics are considered. It is shown that nonequilibrium may become a source of order and that irreversible processes may lead to a new type of dynamic states of matter called "dissipative structures." The thermodynamic theory of such structures is outlined. A microscopic definition of irreversible processes is given, and a transformation theory is developed that allows one to introduce nonunitary equations of motion that explicitly display irreversibility and approach to thermodynamic equilibrium. The work of the group at the University of Brussels in these fields is briefly reviewed. In this new development of theoretical chemistry and physics, it is likely that thermodynamic concepts will play an ever-increasing role.

864 citations