Dynamic behavior modeling for P/M superalloys during hot isostatic pressing
TL;DR: In this paper, a method was developed for the dynamic behavior modeling of P/M superalloys during hot isostatic pressing (HIP) and the power dissipative efficiency during the HIP process was defined as a function of the relative density R and the strain-rate sensitivity index m.
About: This article is published in Journal of Materials Processing Technology.The article was published on 1997-12-07. It has received 6 citations till now. The article focuses on the topics: Hot isostatic pressing.
Citations
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TL;DR: In this paper, the basic science of sintering and hipping is summarized and contrasted, and the current state of understanding and modeling of hipping can be classified either as microscopic or macroscopic in their approach.
Abstract: Hot isostatic pressing (hipping) can be used for upgrading castings, densifying presintered components, consolidating powders, and interfacial bonding. It involves the simultaneous application of a high pressure and elevated temperature in a specially constructed vessel. The pressure is applied with a gas (usually inert) and, so, is isostatic. Under these conditions of heat and pressure, internal pores or defects within a solid body collapse and diffusion bond. Encapsulated powder and sintered components alike are densified to give improved mechanical properties and a reduction in the scatter band of properties. In this article, the basic science of sintering and hipping is summarized and contrasted. The current state of understanding and modeling of hipping is then reviewed. Models can be classified either as microscopic or macroscopic in their approach. In the microscopic approach, the various mechanisms of densification are analyzed in terms of a single particle and its surroundings. In the macroscopic approach, the compact is treated as a continuous medium. In hipping, although the pressure is isostatic, shrinkage is not generally isotropic, particularly if containment is used. However, the shrinkage can now be well predicted, provided that the material and container properties are accurately known.
536 citations
TL;DR: In this paper, the changes in microstructure induced by plastic deformation in hot isostatically pressed (HIPed) P/M Rene 95 under isothermal conditions are discussed.
Abstract: The changes in microstructure induced by plastic deformation in hot isostatically pressed (HIPed) P/M Rene 95 under isothermal conditions are discussed. Results of the constant true strain rate compression tests are presented for initially fine (7 μm) and coarse (50 μm) grained compacts deformed at temperatures of 1050 °C, 1075 °C and 1100 °C and at strain rates in the range from 10 −4 s −1 to 1 s −1 . Under these test conditions, both the fine and coarse-grained compacts recrystallize and their grain size are refined during flow. This grain refinement gives rise to softening in both materials. Ultimately, their microstructures transform into the same equiaxed fine-grained microduplex structure at which point their flow strength becomes identical. Continued deformation at that point produces no further change in grain size or flow strength. Under this steady state regime of deformation, the microduplex grain size and flow strength are independent of the original microstructure but are conditioned by the strain rate at a given temperature. The steady state grain size increases whereas the steady flow strength decreases with a decrease in strain rate and/or an increase in temperature.
33 citations
15 Aug 2006-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the changes in microstructure induced by forging and their influence on flow strength of hot isostatically pressed P/M Rene 95 as revealed by constant strain rate compression tests under simulated isothermal forging conditions are discussed.
Abstract: The changes in microstructure induced by forging and their influence on flow strength of hot isostatically pressed P/M Rene 95 as revealed by constant strain rate compression tests under simulated isothermal forging conditions are discussed. Results are presented for initially fine (7 μm) and coarse (50 μm) grained compacts tested at temperatures of 1050, 1075 and 1100 °C and at strain rates in the range from 10−4 to 1 s−1. Under these test conditions, both the fine and coarse-grained compacts recrystallize and their grain size is refined during plastic deformation. This grain refinement gives rise to softening in both materials. Ultimately, their microstructures transform into the same equiaxed fine-grained microduplex structure at which point their flow strength becomes identical. Continued deformation at that point produces no further change in grain size or flow strength. In this regime of deformation, the microduplex grain size and flow strength are independent of the original microstructure but are conditioned by the strain rate at a given temperature. The steady state grain size increases whereas the steady flow strength decreases with a decrease in strain rate and/or an increase in temperature. It is shown how changes in microstructure and flow strength during isothermal forging can be modelled in P/M Rene 95 compacts by means of established deformation models for predicting peak flow strength, using the steady state deformation data as a boundary condition for the evolution of microstructure and flow strength and a model for deformation-induced recrystallization during forging that has been recently developed for this class of materials.
33 citations
01 Jan 2007
TL;DR: In this article, Ni-based superalloy composite was produced by hot isostatically pressing (HIP) using P/M Rene 95 powders, which was first located into pre-shaped container, then gas evacuated, hot-isostatically pressed and compacted, later on heat treated, and machined to finish.
Abstract: In this study, Ni-based superalloy composite was produced by hot isostatically pressing (HIP) using P/M Rene 95 powders. P/M Rene 95 superalloy powder with low carbon content, which is produced by inert gas atomization, was first located into pre-shaped container, then gas evacuated, hot isostatically pressed and compacted, later on heat treated, and machined to finish. A dual-stage HIP was used to minimize MC carbide precipitation at prior particle boundaries (PPB). Typical microstructure of P/M Rene 95 compacts produced at sub-solvus temperature exhibited a uniform dispersion of a few underformed powder particles in a fine grained microdublex matrix. Later, to investigate the heat treatment effect on grain size, some compacts were applied to heat treatment for 1 hour at a sub solvus temperature of 1100 o C followed by fast cooling. The other compacts were applied grain coarsening treatment of 2 hours at super-solvus temperature of 1200 o C followed by slow cooling. The average grain sizes were measured as 7 µm fine, and 50 µm coarse grains respectively.
TL;DR: In this article, the authors derived the efficiency of power dissipation for PM compacts for any flow stress data and demonstrated it using the test data of PM Rene 95 alloy.
Abstract: The derivation of efficiency of power dissipation for PM compacts is presented. An accurate evaluation of the efficiency parameter for any flow stress data is described and demonstrated using the test data of PM Rene 95 alloy.
References
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09 Mar 1989
TL;DR: In this paper, the finite element method was used to analyze the metal forming process and its properties, including plasticity, viscoplasticity, and plane-strain problems.
Abstract: Introduction Metal forming process Analysis and technology in metal forming Plasticity and viscoplasticity Methods of analysis The finite element method (1) The finite element method (2) Plane-strain problems Axisymmetric isothermal forging Steady state processes of extrusion and drawing Sheet metal forming Thermo-viscoplastic analysis Compaction and forging of porous metals Three dimensional problems Preform design in metal forming Solid formulation, comparison of two formulations, and concluding remarks Index.
1,226 citations
TL;DR: In this article, a hot-compression test was conducted on the temperature range 850-1200°C and strain rate range $0.001-100s^{-1}$ using hot compressive tests.
75 citations
TL;DR: The elastoplastic finite element method for the deformation of porous metals has been newly formulated using the yield condition advanced by Lee and Kim as discussed by the authors, and changes in geometries and densities of porous metal, and upsetting loads with upsetting strain have been calculated.
Abstract: The elastoplastic finite element method for the deformation of porous metals has been newly formulated using the yield condition advanced by Lee and Kim. Changes in geometries and densities of porous metals, and upsetting loads with upsetting strain have been calculated. The Brinell hardnesses of porous metals with various densities dependent on indenting geometries have been analysed. The calculated results were in very good agreement with the measured data. PM/0632
33 citations