Showing papers on "Forging published in 2005"

An investigation of a new near-beta forging process for titanium alloys and its application in aviation components

Abstract: In this paper, the authors present a new near-beta forging process, in which materials are heated at about 15 °C below the beta transus, to improve the combined properties of titanium alloys. Materials processed by the near-beta forging process, followed by rapid water-cooling, then high temperature toughening and low temperature strengthening heat treatments, produce a new kind of microstructure for titanium alloys. This new tri-modal microstructure consists of about 15% equiaxed alpha, 50–60% lamellar alpha and transformed beta matrix. Materials with tri-modal microstructure show a high low cycle fatigue property, high creep-fatigue interaction life, high fracture toughness and a high service temperature without decreasing ductility and thermal stability. The experimental fundamentals of the new process and the strengthening and toughening mechanism have been discussed. A critical issue in the practical application of the near-beta forging process is the control of temperature. A new metallographic inspection method was proposed to solve this problem. This new near-beta forging process has been reliably applied to produce several aeroengine compressor disks, rotators, and other airplane components.

Ultra-fine grain development in an AZ31 magnesium alloy during multi-directional forging under decreasing temperature conditions

Abstract: Grain refinement of a magnesium alloy, AZ31, was studied in multi-directional forging (MDF) with decreasing temperature from 623 to 423 K. The MDF was carried out up to cumulative strains of around 5 with changing the loading direction during decreasing temperature from pass to pass. The structural changes are characterized by the development of many mutually crossing kink bands accompanied by MDF at low strains, followed by full development of very fine grains at high strains. The dynamic changes in grain size evolved can be expressed by two different power law functions of flow stress for the regions of flow stress above or below around 100 MPa. The MDF under decreasing temperature condition can accelerate the uniform development of much finer grains and the improvement in plastic workability, leading to the minimal grain size of 0.36 μm at a final processing temperature of 423 K. The mechanism of grain refinement is discussed in detail.

The microstructural evolution of near beta alloy Ti-10V-2Fe-3Al during subtransus forging

Abstract: The microstructural evolution of titanium alloys during subtransus isothermal forging (IF) has been effectively demonstrated using a testing methodology developed at Imperial College London. Double truncated cone specimen geometries were isothermally deformed at near β transus temperatures to obtain microstructural information for a range of strains within a single specimen. The methodology was applied to the near β alloy, Ti-10V-2Fe-3Al, to determine the effect of strain, strain rate, and IF subtransus temperature on microstructural evolution.

Scaling up of equal-channel angular pressing and its effect on mechanical properties, microstructure, and hot workability of AA 6061

Abstract: Equal-channel angular pressing (ECAP) was performed on aluminum 6061 billets with different cross-sectional areas to study the effect of scaling up on the mechanical properties, microstructure, and the hot workability of the alloy. In this study, annealed AA 6061 was subjected to severe plastic deformation at room temperature by ECAP (Route BC), producing 12.5 mm (0.5 in.), 50 mm (2.0 in.), and 100 mm (4.0 in.) square billets. The mechanical properties and microstructure of as pressed alloy were examined as a function of the extent of deformation and the cross-sectional area of the billets. Also, hot workability was determined by forging industrial parts at various temperatures. Results indicate that the average grain size after ECAP is of the order of 0.5 μm. This grain refinement resulted in enhanced hot workability at 315 °C (600 °F); indicating applicability of ECAP processed material in the forging industry.

Mechanical Properties of Forged Low Ni and C-Containing Co-Cr-Mo Biomedical Implant Alloy

Abstract: In order to examine the influence of variation in grain size and microstructure on mechanical properties of a low Ni and C-containing Co-29Cr-6Mo alloy for biomedical implant materials, the tensile properties and the dry friction wear characteristics of the wrought Co-29Cr-6Mo alloy without addition of Ni and C were investigated. The microstructure of as-forged alloys, consisting of fcc phase mixed with athermal hcp martensite, is found to become finer as the reduction during forging increases. The hot-forging processes for fabricating the fine microstructure with different grain sizes of 43, 11 and 3 μm has been successfully established under the condition that forging temperature of higher than 1273 K is strictly kept during forging. The tensile properties, such as the yield stress, the tensile stress and the elongation, are improved with decreasing the grain size and thereby increasing the volume fraction of the fcc phase in the microstructure. The dry wear resistance against the alumina ball is enhanced by decreasing the grain size.

Metalworking : bulk forming

Abstract: Volume 14A is an indispensable reference for manufacturing, materials, and design engineers. It provides comprehensive coverage and essential technical information on the process-design relationships that are needed to select and control metalworking operations that produce shapes from forging, extrusion, drawing and rolling operations. This engineering reference book is an invaluable reference resource for process and production engineers and industrial (shop-floor) personnel in the automotive, aerospace, and other industries, as well as for students of metal forming. In-depth discussion of forming equipment, processes, materials, and advanced modeling techniques make it a substantially new updated ASM Handbook. Some of the new topics and coverage include: Innovations with forming processes such as equal-channel angular extrusion and advanced roll-forming techniques Forming of special-purpose materials such as intermetallic alloys and composites) Discussion of advanced thermomechanical processes for both ferrous and non-ferrous alloys New articles dealing with process and material-behavior models, process optimization, and the properties of workpiece and die materials Contents includes: Introduction, Forging Equipment, Forging Processes, Cold Heading and Cold Extrusion, Other Bulk Forming Processes, Forging of Steels and Heat-Resistant Alloys, Forging of Nonferrous Metals, Evaluation of Workability, Modeling and Computer Aided Process Design for Bulk Forming, Reference Information.

New Microalloyed Steel Applications for the Automotive Sector

Abstract: Developments related to the use of microalloy additions, primarily of Ti, Nb, and V, and controlled processing are reviewed to illustrate how steels with tailored microstructures and properties are produced from either bar or sheet steels for new automotive components. Microalloying additions are shown to control the necessary strengthening mechanisms to produce high strength materials with the desired toughness or formability for a specific application. Selected examples of direct cooled forging steels, microalloyed carburizing steels, and advanced high strength sheet (AHSS) steels are discussed.

Effect of Forging Ratio and Grain Size on Tensile and Fatigue Strength of Pure Titanium Forgings

Abstract: Pure titanium is expected to be used in high-speed ships in light of its corrosion resistance, high specific strength, ability to reduce ship-dismantling costs, and recyclability. Titanium rudder forgings, each of which is an integrated combination of a rudder plate and a rudder stock, have been used for high-speed ships. Fatigue fractures have often been observed in the rudder stocks. In the context of these fractures, tensile and fatigue tests were performed using forgings with forging ratios of 2 and 4 and different grain sizes. Typical results obtained are summarized as follows : (1) 0.2% proof stresses in the tensile test agreed with the Hall-Petch equation; (2) their slope was approximately equal to that for low-carbon steels ; (3) S-N curves showed that forgings with a forging ratio of 4 were obviously superior in fatigue strength to those with a forging ratio of 2 ; (4) fatigue crack initiation was observed at grain boundaries between large grains, indicating that the decrease in fatigue strength is caused by an inhomogeneous microstructure; and (5) the forging ratio had an obvious effect on fatigue strength rather than on tensile properties.

One-piece steel piston

Abstract: A one-piece steel piston that is made from a piston blank that includes a portion that configured and designed to be displaced to form a cooling gallery and ring belt. The piston blank can be formed by a casting or forging process. The portion that is designed and configured to be displaced is a flange that extends radially at the top of the piston blank. The flange is bent downward so that a peripheral edge of the flange contacts a top portion of the piston skirt. The peripheral edge of the flange and the top portion of the skirt can be welded together or provided with inter-engaging structures.

Sputter targets and methods of forming same by rotary axial forging

Abstract: A method of making sputter targets using rotary axial forging is described. Other thermomechanical working steps can be used prior to and/or after the forging step. Sputter targets are further described which can have unique grain size and/or crystal structures.

Thermal fatigue in hot-working tools

Abstract: Chromium martensitic hot-work tool steel (AISI H13) is commonly used as die material in hot forming techniques such as die casting, hot rolling, extrusion and hot forging. They are developed to endure the severe conditions by high mechanical properties attained by a complex microstructure. Even though the hot-work tool steel has been improved over the years by alloying and heat treatment, damages still occur. Thermal fatigue is believed to be one of the most common failure mechanisms in hot forming tools. In this thesis tools used in hot forging and die casting were examined to determine damage, material response, thermal fatigue crack initiation and propagation. Different chromium martensitic hot-work tool steels, heat treated at four different austenitizing temperatures were experimentally tested in thermal fatigue and isothermal fatigue. The materials were then evaluated using X-ray line broadening analysis and transmission electron microscopy to explore the relation between fatigue softening and the change in microstructure. The high temperature fatigue softening was also simulated using an elasto-plastic, non-linear kinematic and isotropic model. The model was implemented in a numerical simulation to support the integration of die design, tool steel properties and its use. It was found that the dominant damage mechanisms in the investigated tools were thermal fatigue and that tool material experiences a three stage softening at high temperature loading. The primary stage was concluded to be influenced by the dislocation density and the second stage by the temper resistance i.e. carbide morphology. The microstructural changes during the softening stages were also connected to the non-linear kinematic and isotropic model. The general aim of this thesis is to increase the knowledge of the chromium martensitic hot-work tool steel damage, performance and microstructure.

Optimisation of hot die forging processes of Ti-10V-2Fe-3Al alloy

Abstract: In order to optimise the hot die processes of Ti–10V–2Fe–3Al alloy, the effects of forging processes on the microstructures and mechanical properties were studied and processing maps were used to try to aid the process design. The results show that processing maps for Ti–10V–2Fe–3Al alloy exhibit three process ranges, but only the range near β transus is suitable for hot die forging of this alloy. The alloy forged at T β −30°C has a higher strength and ductility while the alloy forged at T β +30°C offers higher fracture resistance than the former. Process C, where the alloy was forged at T β +30°C to form the acicular α p and then at T β −30°C to get globular α p, was designed and the total amount of deformation equal to 50% was chosen. Through process C the alloy has a better combination of tensile properties and fracture resistance than any other processes because a proper mixture between globular α p and acicular α p is obtained.

Eliminating Forging Defects Using Genetic Algorithms

Abstract: In this article, an optimization method for metal forging process designs using finite element-based simulation is presented. Using as entry parameters the specifications of the final product the so-called inverse techniques developed for optimization problems allows the calculation of the optimal solution, the design parameters that produce the required product. An evolutionary genetic algorithm is proposed to calculate optimal shape geometry and temperature. An example demonstrating the efficiency of the developed method is presented considering a two-stage hot forging process. It considers optimization of the process parameters to reduce the difference between the realized and the prescribed final forged shape under minimal energy consumption, restricting the maximum temperature.

Crystal structures and textures of hot forged Ni48Mn30Ga22 alloy investigated by neutron diffraction technique

Abstract: A ferromagnetic shape memory alloy of Ni48Mn30Ga22 prepared by induction melting was successfully hot forged. Strong textures and a large anisotropy of in plane plastic flow were developed during the hot forging process. The crystal structures, both in austenitic and martensitic states, were investigated by means of neutron powder diffraction technique. The result suggests that Ni48Mn30Ga22 has a cubic L21 Heusler structure at room temperature, the same as that in the stoichiometric Ni2MnGa. When cooled to 243 K, the Ni48Mn30Ga22 alloy changes into a seven layered orthorhombic martensitic structure. No substantial change of the neutron diffraction pattern was observed upon further cooling to 19 K, indicating that there is no intermartensitic transformation in the investigated alloy, which is different from the transformation processes in the Ni–Mn–Ga alloys with higher martensitic transformation temperatures.