Design of Low Cost High Performance Powder Metallurgy Titanium Alloys: Some Basic Considerations

The inexpensive hydrogenated–dehydrogenated (HDH) titanium powder made from the Kroll sponge titanium provides a cost-affordable basis for powder metallurgy (PM) Ti alloy development. The design targets we hope to achieve are low feedstock cost (< $25/kg) including all alloying elements; low fabrication cost based on cold compaction and pressureless sintering, and wrought grades of properties of Ti-6Al-4V in the as-sintered state. Relevant issues are considered. These include alloying with inexpensive elements such as Fe and Si, grain size control during heating, isothermal sintering and cooling, chemical homogeneity of as-sintered microstructure, and simultaneous scavenging of oxygen and chlorine. In addition, it is proposed that achieving 6% of tensile elongation will be adequate for most PM Ti applications, compared to PM steels (normally < 2%), PM aluminium alloys (mostly < 4%) and the requirements for wrought Ti-6Al-4V armour plates (≥ 6%). This will allow the use of HDH Ti powder that contains relatively high oxygen (~0.35wt.%) and direct more efforts towards improving other properties.

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Development of Stainless Steel (SS316L) Foam with Different Composition Using Compaction Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1087.86 ◽

2015 ◽

Vol 1087 ◽

pp. 86-90 ◽

Cited By ~ 1

Author(s):

Murni Faridah Mahammad Rafter ◽

Sufizar Ahmad ◽

Rosdi Ibrahim ◽

Rosniza Hussin ◽

H.M. Taib

Keyword(s):

Stainless Steel ◽

Powder Metallurgy ◽

Low Cost ◽

Size Control ◽

Medium Size ◽

Sintering Process ◽

Font Size ◽

Porous Metals ◽

X Ray ◽

Compaction Method

Powder metallurgy stainless steels are retains unique benefits in preparation of porous metals due to its low cost, better wear, precise size control and corrosion resistance which are significant quality displays. In this study, the fabrication of open cellular stainless steel (SS316L) foams by using a crystalline sugar via compaction method was investigated. In this work, we show a promising method of SS316L preparation with crystalline sugar as space holder particles. Then, the foams will be given to consider the properties of SS316L foam after sintering process. Powder metallurgy process needs to go through the mixing, pressing, sintering and analysis. The selected composition of SS316L was 50 wt % and 55 wt % SS316L while the remaining percentages are foaming agent or binder. Then, sintering process was conducted in the tube furnace. The SS316L foams were characterised using X-Ray Diffraction (XRD) and Energy Diffraction X-ray (EDX). The results of this study indicate that, the XRD was detected Austenite stainless steel. Then, the detected elements in the SS316L foam were O, K, Mn, Cr, Fe, Mo and Al.

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Pathways to Optimize Performance/Cost Ratio of Powder Metallurgy Titanium – A Perspective

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.520.15 ◽

2012 ◽

Vol 520 ◽

pp. 15-23 ◽

Cited By ~ 21

Author(s):

Z. Zak Fang ◽

Pei Sun

Keyword(s):

Powder Metallurgy ◽

Low Cost ◽

Cost Ratio ◽

Fine Grain ◽

Main Challenge ◽

Individual Unit ◽

Near Net Shape ◽

The Cost ◽

Sintered State ◽

Ratio Reduction

Powder Metallurgy (PM) Titanium has great potentials as low-cost alternative for Ti manufacturing, but the use of conventional PM processes for producing Ti products is also limited due to reasons related to either that the properties are not as satisfactory as that of equivalent wrought materials, or the cost advantage is not as significant as it was expected. Therefore, the main challenge of developing PM Ti is to increase performance to cost ratio. Reduction of costs and improvement of final products must involve every step of the entire process. This article attempts to assemble a set of processes by selecting individual unit processes that when combined synergistically could offer the optimum performance to cost ratio. This set of processes include using low cost powders, using automatable near-net-shape compaction techniques, and using sintering using sintering technologies that can produce parts with very fine grain sizes, thus satisfactory mechanical properties, in as-sintered state.

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A Novel Forming Process for Powder Metallurgy of Superalloys

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.622-623.833 ◽

2014 ◽

Vol 622-623 ◽

pp. 833-839 ◽

Cited By ~ 2

Author(s):

Qian Bai ◽

Jian Guo Lin ◽

Gao Feng Tian ◽

Daniel S. Balint ◽

Jin Wen Zou

Keyword(s):

Powder Metallurgy ◽

Relative Density ◽

High Performance ◽

Low Cost ◽

Hot Isostatic Pressing ◽

Hot Extrusion ◽

Forming Process ◽

Isostatic Pressing ◽

Wide Range ◽

Forming Temperature

Powder metallurgy (PM) of nickel-based superalloys has been used for a wide range of products owing to their excellent special properties in processing and applications. Typical processes for high performance PM superalloys include hot isostatic pressing, hot extrusion and hot isothermal forging. Hot isostatic pressing is normally conducted at a high temperature, by using a low pressure for a long time in a closed vessel, resulting in high cost and low product efficiency. In this paper a novel forming process, i.e. direct powder forging for powder metallurgy of superalloys has been proposed. In this process, the encapsulated and vacuumed powder is heated up to the forming temperature and forged directly to the final shape, by using a high forming load for a very short time. Direct powder forging is a low-cost and energy-saving process compared to conventional PM processes, and in addition, press machines of conventional forging can be used for direct powder forming process. In direct powder forging it is important to control the relative density of the deformed part since the existence of voids could reduce the mechanical strength and fatigue life. In this paper, feasibility tests of direct powder forging are presented. Microstructure, relative density and hardness of the formed specimen were studied.

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Processing and Alloy Development to Optimise the Properties and Cost-Effectiveness of Components Manufactured from TiAl-Based Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.449-452.25 ◽

2004 ◽

Vol 449-452 ◽

pp. 25-30 ◽

Cited By ~ 4

Author(s):

Xin Hua Wu ◽

D. Hu ◽

M.H. Loretto

Keyword(s):

Grain Size ◽

Powder Processing ◽

Thermomechanical Processing ◽

Plastic Anisotropy ◽

Lamellar Microstructure ◽

Size Control ◽

Research Programme ◽

Alloy Development ◽

Grain Size Control ◽

Fully Lamellar

The IRC has carried out a major research programme over the last ten or so years aimed at developing the processing and optimisation of TiAl-based alloys. This work has covered melting, the production of shaped castings, powder processing and a range of thermomechanical processing routes in parallel with alloy development. In this paper the work aimed at understanding the factors that influence the properties of thermo-mechanically processed and cast samples of TiAl-based alloys will be reviewed. It is shown that the use of boron to control the grain size of castings leads to limited ductility in the stronger and more highly alloyed TiAl alloys because ribbon-like borides up to 200µm in length can be formed. It is also shown that although a fully lamellar microstructure offers a good balance of properties their plastic anisotropy leads to pre-yield fracture and to reduced fatigue life. It is clear that grain size control is essential if an acceptable balance of properties is to be obtained but that if casting is to be used grain refinement via boron addition is not totally satisfactory. A simple heat treatment can be used to refine the microstructure of cast boron-free alloys, which leads to ductility comparable with that in wrought samples and the associated convoluted microstructure should also eliminate pre-yield cracking.

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Grain size control for high-performance formamidinium-based perovskite solar cells via suppressing heterogenous nucleation

Journal of Materials Chemistry C ◽

10.1039/d0tc04833j ◽

2021 ◽

Vol 9 (1) ◽

pp. 208-213

Author(s):

Xiaoxiao Xu ◽

Yuhai Sun ◽

Dingchao He ◽

Zheng Liang ◽

Guozhen Liu ◽

...

Keyword(s):

Grain Size ◽

Solar Cells ◽

Homogeneous Nucleation ◽

High Performance ◽

Defect Density ◽

Perovskite Solar Cells ◽

Size Control ◽

Precursor Solution ◽

Grain Size Control ◽

Heterogenous Nucleation

By introducing ED and TAP into precursor solution, homogeneous nucleation is encouraged to occur and films with large grain size and lower defect density were obtained.

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Nanoscale Gd-Doped CeO2 Buffer Layer for a High Performance Solid Oxide Fuel Cell

Journal of Fuel Cell Science and Technology ◽

10.1115/1.4003016 ◽

2011 ◽

Vol 8 (4) ◽

Cited By ~ 7

Author(s):

Cornelia Endler-Schuck ◽

André Weber ◽

Ellen Ivers-Tiffée ◽

Uwe Guntow ◽

Johannes Ernst ◽

...

Keyword(s):

Thin Films ◽

Buffer Layer ◽

High Performance ◽

Large Scale ◽

State Of The Art ◽

Low Cost ◽

Buffer Layers ◽

Chemical Homogeneity ◽

Ohmic Resistance ◽

Screen Printed

Gd 2 O 3 -doped ceria (GCO) is irreplaceable as interface/buffer layer between a mixed conducting cathode such as La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) and an 8 mol %Y2O3 stabilized ZrO2 (8YSZ) thin film electrolyte. To meet the demands of high performance, indispensable characteristics of this interface (LSCF/GCO/8YSZ) are (i) no reaction of GCO with LSCF or YSZ and (ii) a GCO layer that is defect-free (closed porosity, no cracks). It is well known that state-of-the-art screen printed and sintered GCO buffer layers are imperfect and ultimately reduce the overall performance. This study concentrates on the evaluation of nanoscaled GCO thin films integrated into anode supported cells (ASC). GCO thin films were deposited on 8YSZ electrolyte by a low temperature metal organic deposition (MOD) process. MOD is preferable because it is a versatile technique for large scale and low cost fabrication for various material compositions. The authors investigated the influence of preparation parameters with respect to chemical homogeneity and film quality (pores, cracks) of GCO thin films with a constant film thickness between 50 nm and 100 nm. Electrochemical performance of anode supported cells employing MOD derived GCO thin films will be presented in terms of ohmic resistance (ASRΩ) and will be evaluated in contrast to screen printed and sintered GCO thick films. Nanoscale MOD derived thin films with low processing temperatures and dense film qualities were vastly superior to state-of-the-art GCO and beneficial to the overall cell performance.

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Interstitial Control in Titanium Alloys Produced by Powder Metallurgy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.660-661.3 ◽

2010 ◽

Vol 660-661 ◽

pp. 3-10 ◽

Cited By ~ 3

Author(s):

Vinicius André Rodrigues Henriques ◽

S.L.G. Petroni ◽

M.S.M. Paula ◽

Carlos Alberto Alves Cairo ◽

Eduardo T. Galvani

Keyword(s):

Powder Metallurgy ◽

Titanium Alloys ◽

High Performance ◽

Low Cost ◽

Cold Isostatic Pressing ◽

Mechanical Resistance ◽

Aerospace Applications ◽

Surgical Implants ◽

Critical Issues ◽

Interstitial Elements

The titanium alloys are used for applications that demand high performance, including surgical implants and aerospace applications. Powder metallurgy is an advantageous alternative for titanium parts production with complex geometries at a relative low cost. Despite that, it is verified that the introduction of interstitial elements (oxygen, nitrogen and carbon) wile processing these alloys, though can increase hardness and mechanical resistance, which is frequently related to the reduction of ductility and fragility increase. The objective of this work is to investigate the influence of the interstitial elements in commercially pure Ti and Ti-13Nb-13Zr alloy produced by powder metallurgy (P/M). Samples were produced by the mixing of hydrided metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering at 1400 °C, in vacuum. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. The interstitial content was analyzed by Leco equipment. It was shown that the samples were sintered to high densities with a Widmanstatten microstructure. The oxygen and nitrogen contents are above the ELI (Extra Low Interstitial) and the critical issues were identified in the original blended elemental route.

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Powder Metallurgy Ti-6Al-4V Alloy with Wrought-Like Microstructure and Mechanical Properties by Hydrogen Sintering

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.704.3 ◽

2016 ◽

Vol 704 ◽

pp. 3-14 ◽

Cited By ~ 2

Author(s):

Matt Dunstan ◽

Z. Zak Fang ◽

Mark Koopman ◽

James Paramore

Keyword(s):

Mechanical Properties ◽

Powder Metallurgy ◽

Low Cost ◽

Lamellar Microstructure ◽

Sintering Atmosphere ◽

Powder Metallurgy Process ◽

Partial Pressures ◽

Kinetics Of ◽

Sintered State ◽

Metallurgy Process

Hydrogen sintering phase transformation (HSPT) is a low-cost, blended elemental, press and sinter powder metallurgy process. During HSPT, compacts of TiH2 powder are sintered in dynamically controlled partial pressures of hydrogen followed by a vacuum anneal (dehydrogenation). The use of hydrogen in the sintering atmosphere allows phase transformations in the Ti – H system to create an ultra-fine lamellar microstructure in the as-sintered state with mechanical properties that exceed ASTM standards. Additionally, the fine lamellar structure allows for secondary heat treatments to produce wrought-like microstructures. The removal of hydrogen in the dehydrogenation step is critical to prevent hydrogen embrittlement. The kinetics of dehydrogenation are discussed, in which a model for the concentration profile and an empirical equation for maximum hydrogen concentration as a function of time and size are developed.

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Interfacial studies in Nb3Sn superconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087264 ◽

1991 ◽

Vol 49 ◽

pp. 590-591

Author(s):

Ernest L. Hall ◽

Lee E. Rumaner ◽

Mark G. Benz

Keyword(s):

Grain Size ◽

Grain Boundaries ◽

Flux Pinning ◽

Size Control ◽

High Magnetic Fields ◽

Type Ii ◽

Reaction Interface ◽

Liquid Diffusion ◽

Type Ii Superconductor ◽

Grain Size Control

The intermetallic compound Nb3Sn is a type-II superconductor of interest because it has high values of critical current density Jc in high magnetic fields. One method of forming this compound involves diffusion of Sn into Nb foil containing small amounts of Zr and O. In order to maintain high values of Jc, it is important to keep the grain size in the Nb3Sn as small as possible, since the grain boundaries act as flux-pinning sites. It has been known for many years that Zr and O were essential to grain size control in this process. In previous work, we have shown that (a) the Sn is transported to the Nb3Sn/Nb interface by liquid diffusion along grain boundaries; (b) the Zr and O form small ZrO2 particles in the Nb3Sn grains; and (c) many very small Nb3Sn grains nucleate from a single Nb grain at the reaction interface. In this paper we report the results of detailed studies of the Nb3Sn/Nb3Sn, Nb3Sn/Nb, and Nb3Sn/ZrO2 interfaces.

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