Showing papers by "Wayne Eric Voice published in 2004"
TL;DR: In this article, the effects of processing conditions, such as laser power, scan speed, powder feed rate, etc. on the microstructure of the build have been assessed and it has been found that Ti-6Al-4V is very susceptible to the formation of columnar grains during laser deposition.
372 citations
TL;DR: In this article, the effect of machining surface roughness on fatigue performance was investigated for a variety of workpiece materials and post-machining surface treatments, such as shot peening.
Abstract: The paper reviews published data which address the effect of machining (conventional and non-conventional processes) and the resulting workpiece surface topography/integrity on fatigue performance, for a variety of workpiece materials. The effect of post-machining surface treatments, such as shot peening, are also detailed. The influence of amplitude height parameters (Ra, Rt), amplitude distribution (Rsk) and shape (Rku) parameters, as well as spatial (Std, Sal) and hybrid (Ssc) measures, are considered.
There is some disagreement in the literature about the correlation between workpiece surface roughness and fatigue life. In most cases, it has been reported that lower roughness results in longer fatigue life, but that for roughness values in the range 2.5–5 μm Ra it is primarily dependent on workpiece residual stress and surface microstructure, rather than roughness. In the absence of residual stress, machined surface roughness in excess of 0.1 μm Ra has a strong influence on fatigue life. Temperatures above 400 °C reduce the effects of both residual stress and surface roughness on fatigue, due to stress relieving and the change in crack initiation from the surfaces to internal sites. The presence of inclusions an order of magnitude larger than the machined surface roughness generally overrides the effect of surface topography.
371 citations
TL;DR: In this paper, the response of a recently developed burn-resistant Ti alloy to direct laser fabrication has been assessed and the influence of laser processing conditions on the microstructure and on the tensile properties at room and at elevated temperatures and the creep properties has been investigated.
80 citations
TL;DR: In this article, the electrical discharge surface alloying/modification of γ-TiAl (Ti 46.5Al-4(Cr, Nb, Ta, B)) and α/β Ti alloy (Ti 6Al−4V) sheet (1.mm thick) during wire cutting using deionised water dielectric with nickel and copper wires is described.
66 citations
Patent•
31 Mar 2004TL;DR: In this article, a core is applied to the core prior to placing in the mould, which coating bonds to the hollow structure formed, during the hot isostatic pressing, to form the internal coating.
Abstract: Forming a hollow structure having an internal coating includes the steps of placing a core shaped to form the internal surface of the structure in a mould, filling the mould with a material powder, hot isostatically pressing the powder about the mould to consolidate the powder, and removing the core from the hollow structure formed, wherein a coating is applied to the core prior to placement in the mould, which coating bonds to the hollow structure formed, during the hot isostatic pressing, to form the internal coating.
20 citations
Patent•
09 Aug 2004Abstract: A gamma titanium aluminide alloy consisting of 46 at % aluminium, 8 at % niobium, up to 0.07 at % carbon and the balance titanium plus incidental impurities has an alpha transus temperature T α =1335° C. The gamma titanium aluminide alloy was heated to a temperature T 1 =1360° C. and was held at T 1 =1360° C. for 1 hour or longer. The gamma titanium aluminide alloy was fluidised bed, or salt bath, quenched to a temperature T 2 , where 900° C.
13 citations
25 Oct 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, it was shown that the heat treatment of near γ-TiAl in a silica capsule under low oxygen partial pressure at 1283 K for 50h produces a thin (1-2-μm) Ti 5 Si 3 external film on the sample.
Abstract: It is shown that the heat-treatment of near γ-TiAl in a silica capsule under low oxygen partial pressure at 1283 K for 50 h produces a thin (1–2 μm) Ti 5 Si 3 external film on the near γ-TiAl specimen. This layer confers significant improvements in oxidation resistance for at least 500 h in air at 1173 K. The silicide layer is thought to be produced as the result of gaseous transport of SiO from the walls of the silica vessel to the specimen surface and its reaction there. However, the production of SiO requires that particularly low values of oxygen partial pressure develop within the silica capsule. Mechanisms whereby this can be achieved are discussed but the likely process involves the solution of oxygen within the specimen. The outcome is that the heat-treatment procedure represents a cost-effective CVD-type process for enhancing the oxidation resistance of near γ-TiAl intermetallics.
11 citations
Patent•
21 Dec 2004
TL;DR: In this article, a method of manufacturing an article by consolidating powder material comprises forming a non-deformable tool (12) and a deformable tool(14), which is used to make compressor blades, compressor vanes or compressor blisks for gas turbine engines.
Abstract: A method of manufacturing an article by consolidating powder material comprises forming a non-deformable tool (12) and a deformable tool (14). The non-deformable tool (12) comprises a plurality of tool parts (16,18). The non-deformable tool (12) defines a first cavity (20) having an open end (22) and the first cavity (20) corresponds in shape to that of the article. The non-deformable tool (12) is encapsulated in the deformable tool (14) and the non-deformable tool (12) and the deformable tool (14) define a second cavity (24) interconnected with the first cavity (20). The first and second cavities are filled with powder material (26). The deformable tool (14) is evacuated and sealed. Heat and pressure are applied to the deformable tool (14) and non-deformable tool (12) to consolidate the powder material (26) to form an article (30) in the first cavity (20) of the non-deformable tool (12). The method is used to make compressor blades, compressor vanes or compressor blisks for gas turbine engines.
10 citations
Patent•
27 Jul 2004
TL;DR: An alloy component 10 comprises a first portion 20 and a second portion 22 as discussed by the authors, the composition of the first and second alloys being different, at least one of the portions of the component is made by consolidating a powder of the respective alloy.
Abstract: An alloy component 10 comprises a first portion 20 and a second portion 22. The first portion comprises a first alloy and the second portion comprises a second alloy, the composition of the first and second alloys being different. At least one of the portions of the component is made by consolidating a powder of the respective alloy. The component can be a gas turbine engine turbine blade and the consolidation process can be hot isostatic pressing. Examples of alloys used are niobium silicides and nickel aluminides.
6 citations
TL;DR: In this article, the authors used transmission electron microscopy (TEM) to examine the dislocation structure in α grains and confirmed the presence of dislocations using Burgers vectors containing a c component.
Abstract: Samples of Ti–6 wt% Al–4 wt% V and Timet 550 (Ti–4 wt% Al–4 wt% Mo–2 wt% Sn–0.5 wt% Si) have been subjected to strain rates between 10−1 and 103 s−1and detailed examination of the dislocation structure in the α grains has been carried out using transmission electron microscopy (TEM). For samples deformed to a strain of 0.1 at 10−1 s−1, detailed analysis of the defects can be carried out using all diffracting vectors and the presence of (c + a) dislocations and a dislocations thus confirmed. In contrast, for samples strained to the same strain of 0.1 but at 5 s−1, it is not possible to obtain images of dislocations when using any diffracting vectors other than 0002. Thus the presence of dislocations which have a Burgers vector containing a c component can be confirmed in the samples strained at 5 s−1 but the presence of a-component dislocations can only be inferred from TEM of these samples because of the difficulty of obtaining images with diffracting vectors other than 0002. Limited observations on sampl...
2 citations
Patent•
23 Dec 2004TL;DR: In this paper, a relatively thin in situ brazing alloy layer upon first and second component edges which are brought together in order to create a component joint is presented. But the method is limited to a limited depth, and the properties of the underlying component material structure are maintained.
Abstract: In order to avoid excessive internal stress and micro structure problems inherent with previous fusion welding techniques utilised for component structure fabrication, the present method creates a relatively thin in situ brazing alloy layer upon first and second component edges which are brought together in order to create a component joint. This in situ brazing alloy layer (6, 23, 26) is created by deposition of brazing elements, such as copper or nickel, from an electrical discharge cutting process electrode depletion utilised in order to cut the component edges. A subsequent brazing technique then creates through interstitial migration between that brazing alloy layer and the underlying material substrate of the components a robust component joint. Furthermore, the in situ brazing alloy layer penetrates the respective component cut edge surface to only a limited depth such that the geometric effect is similarly limited, and the properties of the underlying component material structure are maintained.
Patent•
23 Dec 2004TL;DR: In this paper, a relatively thin in situ brazing alloy layer upon first and second component edges which are brought together in order to create a component joint is presented. But the method is limited to a limited depth, and the properties of the underlying component material structure are maintained.
Abstract: In order to avoid excessive internal stress and micro structure problems inherent with previous fusion welding techniques utilised for component structure fabrication, the present method creates a relatively thin in situ brazing alloy layer upon first and second component edges which are brought together in order to create a component joint. This in situ brazing alloy layer (6, 23, 26) is created by deposition of brazing elements, such as copper or nickel, from an electrical discharge cutting process electrode depletion utilised in order to cut the component edges. A subsequent brazing technique then creates through interstitial migration between that brazing alloy layer and the underlying material substrate of the components a robust component joint. Furthermore, the in situ brazing alloy layer penetrates the respective component cut edge surface to only a limited depth such that the geometric effect is similarly limited, and the properties of the underlying component material structure are maintained.