Powder Forging Process Research Articles

Effect of yttria content on microstructural evolution, mechanical properties and temperature dependent strengthening mechanisms in 9Cr-oxide dispersion strengthened (ODS) steel developed by hot powder forging

9Cr-oxide dispersion strengthened (ODS) ferritic/martensitic steel with varying yttria (Y2O3) contents (0, 0.35, 0.5, and 1 wt%) were prepared by mechanical alloying followed by hot powder forging. The powder forged samples were subsequently normalized and tempered by a standard heat treatment. The microstructure consisted of a dual phase structure of tempered martensite and residual ferrite, along with fine distribution of carbides (MC/M23C6). The grain size was strongly influenced by the yttria contents. Tensile tests were conducted at room temperature, 300°C, 500°C, and 700°C for all the compositions. A trend of increasing tensile strength and decreasing total elongation was observed with increase in yttria contents at all the temperatures. Contrary to the results in literature, superior ductility and a comparable tensile strength of ODS steels with the higher yttria contents (≥0.5 wt%) at room as well as high temperatures indicate the benefits of the powder forging process. As per the quantitative estimation of yield strength at room as well as elevated temperature via strengthening mechanisms, root mean square method (σrms) is proven more reliable than linear superposition method (σls). Additionally, strength from grain boundaries, dislocation density, and Orowan was found major at room temperature while dispersoids seemed to be prevailed at high temperature.

Full density graphite/copper-alloy matrix composite fabricated via hot powder forging for pantograph slide

High-performance copper-based pantograph slide materials play a crucial role in the rapid development of modern urban rail transit urgently. Herein, a full density graphite/copper-alloy matrix composite for pantograph slide has been successfully obtained by the hot powder forging process. The composite exhibits the full density when forging energy density is 307.6 J cm−3. In addition, the influence of different aging treatments on microstructure and mechanical performances of the composite has been studied in detail. The hardness and resistivity of the forged materials are greatly improved after an optimum aging treatment. Simultaneously, the friction and wear performances with or without currency current have been investigated, which demonstrates the friction coefficient can reach the minimum of 0.109 under 35 N. In current-carrying friction, the wear rate of the composite is an extremely small value of 5.5 × 10–5 mg m−1 after the aging treatment, indicating the outstanding anti-friction and self-lubricating performance. All the comprehensive analyses illustrate the full density graphite/copper-alloy matrix composite with excellent mechanical shows an enormous potential for pantograph slide.

Preliminary study on the fabrication of 14Cr-ODS FeCrAl alloy by powder forging

A simple powder forging process was presented herein to fabricate an Fe-14Cr-4.5Al-2W-0.4Ti-0.5Y2O3 ODS FeCrAl alloy. The forged alloy exhibits a high density that exceeds 97 % of the theoretical density. The ODS alloy was investigated in terms of the residual porosity, morphology and phase structure of oxide nanoparticles, impact toughness and tensile properties. It was found that refined grains were obtained during powder forging. A residual porosity less than 1.1 % has no impact on the precipitation of oxide nanoparticles. The average diameter of the oxide particles is 7.99 nm, with a number density of 2.75 × 1022 m−3. Almost all of the oxides are identified as orthorhombic YAlO3 particles. The refined grains and uniformly distributed oxide nanoparticles enable the alloy to show excellent mechanical strength and ductility below 700 °C, and enable the ductile-to-brittle transition temperature to be close to room temperature. However, a slight decrease in strength at 1000 °C and the Charpy upper shelf energy has been suggested to be due to the residual porosity. These results indicate that powder forging can be used as a promising technique for the fabrication of ODS alloys.

Microstructure and Mechanical Properties of Ti-5Al-2.5Fe Alloy Produced by Powder Forging

Blended elemental powder metallurgy is a cost effective approach to produce near net shape titanium alloy parts; however, the residual pores remaining in sintered parts are detrimental to the mechanical properties. In this study, elemental powders (Ti, Al and Fe) were used to produce the Ti-5Al-2Fe alloy by a powder forging process, involving cold compaction, vacuum sintering, forging and heat treatment. The residual pores of the sintered parts were removed completely by forging at the temperature of 1250oC. The effect of solution and aging and mill annealing heat treatments on the mechanical properties of the forged Ti-5Al-2Fe parts were studied. It is found that the ductility of the forged Ti-5Al-2Fe parts is improved significantly by both solution and aging treatment and mill annealing, without decreasing their ultimate tensile strength, which sits around 1000 MPa. The enhancement of the mechanical behaviour is justified via understanding the evolution of the residual porosity and of the microstructural features of the materials.

Density-based constitutive modelling of P/M FGH96 for powder forging

A set of viscoplastic constitutive equations is presented in this study to predict hot compressive deformation behaviour and densification levels of powder metallurgy (P/M) FGH96 nickel-base superalloy during direct powder forging (DPF) process. The constitutive equations make use of the elliptic equivalent stress proposed in porous material models, and unify the evolution of relative density, normalised dislocation density, isotropic hardening and flow softening of the powder compact. A gradient-based optimisation technique is adopted to determine the material constants using the experimental data obtained from Gleeble isothermal uniaxial compression tests of HIPed FGH96 at different temperatures and strain rates. The developed constitutive equations are incorporated into finite element code DEFORM via user-defined subroutine for coupled thermo-mechanical DPF process modelling. The constitutive equations benefiting from the viscoplastic densification model of the calibrated Abouaf, among the six studied porous material models, compare favourably with the experimental data, while the equations integrating the porous material model of Shima and Oyane provide excellent agreement with experiments in the low density outer region of the powder compact.

Methodology for Modelling Diffusion Bonding in Powder Forging

Interfacial bonding has a significant influence on the quality of processed components formed by powder forging. Consequently, modelling the bonding process is important for controlling the condition of the components and predicting optimum forging process parameters (e.g. forming load, temperature, load-holding time, etc.). A numerical model was developed in the present work to simulate diffusion bonding (DB) during the direct powder forging (DF) process. A set of analytical equations was derived and implemented in the finite element (FE) software Abaqus via a user-defined subroutine. The DB model was validated using a two-hemisphere compression simulation. The numerical results demonstrated that the DB model has the ability to: 1) determine the bonding status between powder particles during the forging process, and 2) predict the optimum value for key powder forging process parameters. The DB model was also implemented in a representative volume element (RVE) model which was developed in an earlier work to simulate the powder forging process by considering particle packing and thermo-mechanical effects.

Analysis of the Powder Forging Processes for Vehicle Timing Belt Pulley by Finite Element Analysis

This paper uses finite element analysis to analyze the changes in mechanical properties and micro structural characteristics of vehicle timing belt pulleys, which is a key component of vehicles engines, made using powder forging processes. The timing belt pulley is an important part that transfers the power generated by the engine to the drive shaft of the valve. The process happens as follows: The powder is inserted into a forging mold, and the product is formed from compression and finally sinter heat-treated in a high-temperature heat treatment furnace. This study aims to perform 3D modeling to analyze the forging process at each stage, then predict the changes in mechanical properties of the product in the subsequent heat treatment process through numerical analysis. The results of analysis will give the load upon the mold punch, product density, temperature distribution and stress and deformation distributions as the result of stroke changes during forging. Next, structural change and temperature distribution according to cooling rate will be found for various individual cross sections following the heat treatment process. The results will allow testing the effectiveness of powder forging process analysis.Keywords: Finite Element Analysis, Forging Processes, Powder Vehicle, Timing Belt Pulley

A study of direct forging process for powder superalloys

Powder metallurgy (PM) processing of nickel-based superalloys has been used for a wide range of near net-shape fine grained products. In this paper a novel forming process, i.e. direct forging of unconsolidated powder superalloys is proposed. In this process, encapsulated and vacuumed powder particles are heated up to a forming temperature and forged directly at high speed to the final shape, by using a high forming load. Experiments of direct powder forging have been conducted on an upsetting tool-set. Microstructure, relative density and hardness of the formed specimen have been investigated. A finite element model of the direct powder forging process has been established in DEFORM and validated by the comparisons of experimental with simulation results of load variation with stroke as well as relative density distribution. The stress state and the relative density variation have been obtained from FE simulation. The correlation between the stress and consolidation condition has been rationalised. The developed FE model can provide a guide to design the geometry and thickness of preform for direct powder forging.

The Development of Aluminum Alloy Piston for Two-Stroke Cycle Engine by Powder Forging

The purpose of this paper is to investigate the influences on mechanical properties of two-stroke cycle motor pistons manufactured by casting, conventional forging and powder forging, through the comparison of characteristics, merits and disadvantages of each forming technology. For each forming technology, the optimal process parameters were determined through the experiments for several conditions, and microstructure, hardness, tensile strength and elongation of pistons are compared and analyzed. In conventional forging process, material temperature was <TEX>$460^{\circ}C$</TEX> and the die temperature was <TEX>$210^{\circ}C$</TEX> for the Al 4032. The optimal condition was found as solution treatment under <TEX>$520^{\circ}C$</TEX> for 5 hours, quenching with <TEX>$23^{\circ}C$</TEX> water, and aging under <TEX>$190^{\circ}C$</TEX> for 5 hours. In powder forging process, the proper composition of material was determined and optimal sintering conditions were examined. From the experiment, 1.5% of Si contents on the total weight, <TEX>$580^{\circ}C$</TEX> of sintering temperature, and 25 minutes of sintering time were determined as the optimal process condition. For the optimal condition, the pistons had 76.4~78.3 [HRB] of hardness, and 500 [MPa] of tensile strength after T6 heat treatment.

Study on the Maximum Forging Load and Final Face Width of Powder Spur Gear Forging

Powder forging combines powder metallurgy and forging technology, thus possess the advantages of both processes that result in both stronger and yet more versatile products with complicated geometry and arbitrary alloy compositions. For complete filling up, predicting the power requirement and final face width is an important feature of the powder forging process. In this paper, a finite element method is used to investigate the forging force, the final face width and the density variation of the spur gear powder forging process. In order to verify the FEM simulation results, the experimental data are compared with the results of the current simulation for the forging force and the final face width of spur gear. The influences of the parameters such as modules, number of teeth, the initial relative density, the ratio of the height to diameter of billet and friction factor on the forging force and the final face width of the billets are also examined.

Microstructures and mechanical properties of titanium alloy connecting rod made by powder forging process

A new powder metallurgy (P/M) titanium alloy connecting rod with the composition of Ti–1.5Fe–2.25Mo (wt.%), formed by a powder forging process, was successfully developed with the help of a pre-processing simulation using a commercial finite element software (DEFORM-3D). The microstructures and the mechanical properties of the deformed material were evaluated. The results indicate that the microstructures of the crank pin end, fork part and piston pin end are lamellar α + β structures and the microstructure of shank is of through-transus bi-modal phase. The tensile strength and elongation are much higher than those of the most widely used PF-11C50/60 steels, and can well meet the requirements of the connecting-rod industry.

유한요소해석을 이용한 알루미늄분말단조 피스톤 성형해석에 관한 연구

Powder metallurgy processes are used to form Net-Shape products and have been widely used in the production of automobile parts to improve its manufacture productivity. Powder-forging technology is being developed rapidly because of its economic merits and because of the possibility of reducing the weight of automobile parts by replacing steel parts with aluminum ones, in particular while manufacturing automotive parts. In the powder-forging process, the products manufactured by powder metallurgy are forged in order to remove any pores inside them. Powderforging technology can help expand the applications of powder metallurgy; this is possible because powder-forging technology enables the minimization of flashes, reduction of the number of stages, and possible grain refinement. At present, powder forging is widely used for manufacturing primary mechanical parts as in combination with the technology of powder forging of aluminum alloy pistons.

Neural network approach for the selection of processing parameters of aluminium—iron composite preforms during cold upsetting

The powder forging process of die forging, sintering, and upsetting is a convenient way of reducing or eliminating the porosity from traditional powder metallurgy products. Forging of metal powder enhances the demanding high-tensile, impact, and fatigue strength of powder metallurgy products. In this research, a demonstration system has been developed that employs a neural network for advising aluminium—iron composite compositions and optimum process settings with desired properties at an early stage in the design of the component. The input comprises the desired mechanical properties, such as formability index, and the system employs these data as inputs in order to recommend suitable metal powder compositions and process settings such as the particle size, percentage of iron content, preform density, aspect ratio, and compact load. The training data were collected by the experimental set-up in the laboratory for the sintered aluminium—iron composite preforms. Comparison of predicted and experimental data has confirmed the accuracy of the neural network approach; therefore, a new way for recommending suitable metal powder compositions and process settings is explored.

A sensitivity analysis of powder forging processes

The purpose of this paper is to analyze the sensitivity problems in metal forming of rigid-visco-poroplastic materials. A repressing powder forging process is analyzed. Parameter sensitivity, material derivative, and control volume approaches to shape sensitivity analysis are presented, analyzed, and compared. Discretization of the continuum expressions is presented. The numerical solutions for parameter sensitivity in forging problems have been described. Numerical examples concerning simple compression test of cylindrical porous specimen are presented.

Re‐identification problems in forming of rigid‐visco‐poroplastic materials

AbstractA unified approach for parameter identification of a visco‐poroplastic material model is presented. A repressing powder forging process is analyzed. The numerical solutions for direct and inverse problems have been described. The inverse problem is solved by the use of gradient‐based methods and a sensitivity analysis. Numerical examples of the method proposed are presented, in which one and two parameters of the visco‐poroplastic material model were identified. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Processing and Properties of Al Based Amorphous/Crystalline Alloy Composites

Three types of composite materials, Al-10Ni-6Ce (at%)/pure Al (Vf=0.3), Al-10Ni- 6Ce/Al-3.6Mn (Vf=0.3) and Al-10Ni-6Ce/Al-5.5Mg (Vf=0.3), and monolithic Al-10Ni-6Ce alloy were successfully fabricated to a fully dense rod-shaped bulk form having a diameter of about 10mm by adopting a powder forging or extrusion process using amorphous Al-Ni-Ce powder together with crystalline pure Al, Al-Mn and Al-Mg powders. The monolithic Al-Ni-Ce specimen forged at 648K showed a very high compressive strength of 1.3GPa without exhibiting any compressive plastic strain. All of the composite specimens forged at 648K gained a compressive plastic strain with the considerable sacrifice of strength. In contrast, Al-Ni-Ce/Al-Mg composite specimen extruded at 648K showed a noticeably high compressive strength of 1.2GPa with the compressive plastic strain of 0.5%. The extruded Al-Ni-Ce/Al-Mn composite specimen also exhibited a considerably high compressive strength (1.1GPa) accompanied with plastic strain (0.2%).

Microstructure and compressive behavior of Al-base amorphous/nanocrystalline alloys fabricated by powder forging

Al-base amorphous/nanocrystalline bulk alloy rods composed of Al–10Ni–6Ce (numbers indicate at.%) matrix alloy and Al–4Fe–0.6Mo–1.1V–0.3Zr alloy particles (volume fraction = 0.3) were fabricated by a powder forging process. The starting materials were rapidly quenched, powder-shaped amorphous Al–10Ni–6Ce alloy and nanocrystalline Al–4Fe–0.6Mo–1.1V–0.3Zr alloy. The amorphous alloy powders were prepared by the pulverization of melt-spun ribbons, and the nanocrystalline alloy powders were fabricated by using a gas atomization technique. The powder forging process involved pre-compaction of the amorphous/crystalline powder mixtures by cold pressing and subsequent forging at temperatures ranging from 623 to 773 K with a pressure of 0.66 GPa and a strain rate of 10 −2 s −1 to produce the rod-shaped bulk hybrid alloys having a diameter of 10 mm. Bulk monolithic Al–10Ni–6Ce alloys having the same shape were also fabricated by using a similar process to that used for the hybrid ones. Fully dense bulk rods with a porosity of less than 2% were achieved for all of the forged monolithic and hybrid alloys. A remarkably high compressive strength of about 1.2 GPa along with a compressive plastic strain of 1% was obtained at room temperature for the bulk hybrid specimen forged at 648–673 K. In contrast, the bulk monolithic specimen forged at 648–723 K did not exhibit any compressive plastic strain, although it possessed a very high compressive strength of approximately 1.34 GPa.

Synthesis and Properties of Bulk Amorphous/Nanocrystalline Aluminum Alloy Composites

The rod-shaped bulk composites consisting of Al-10Ni-6Ce and Al-4Fe-0.6Mo-1.1V- 0.3Zr alloy (mixing ratio; 0.7:0.3, 0.5:0.5 and 0.3:0.7) and corresponding monolithic alloys were produced to a full density via powder forging process. The process involved pre-compaction of rapidly solidified alloy powders and subsequent isothermal forging at 673K. The forged Al-10Ni- 6Ce alloy exhibited nano-scaled crystalline particles, such as fcc-Al, Al3Ni, Al4Ce and Al11Ce3 phase, coexisting with an amorphous phase. In the case of the forged Al-4Fe-0.6Mo-1.1V-0.3Zr alloy, an equiaxed grain structure was observed to exist with uniformly distributed nano-scaled Al- Fe based intermetallics. The monolithic Al-10Ni-6Ce alloy had a considerably high maximum compressive strength (MCS) of 1.35 GPa without showing any compressive plastic strain (CPS). In contrast, the monolithic Al-4Fe-0.6Mo-1.1V-0.3Zr alloy possessed noticeably high CPS of 25% with the MCS of 0.71GPa. The composites acquired the CPS varying from 1 to 5.8 % and the MCS from 1.26 to 0.74 GPa, with increment of the volume fraction of Al-4Fe-0.6Mo-1.1V-0.3Zr alloy from 0.3 to 0.7.

Fabrication and Property of Amorphous/Nano Crystalline Al&lt;sub&gt;84&lt;/sub&gt;Ni&lt;sub&gt;10&lt;/sub&gt;Ce&lt;sub&gt;6&lt;/sub&gt; Bulk Alloy by a Powder Forging

The bulk Al84Ni10Ce6 alloy was fabricated by a powder forging process. The process involved pre-compaction of amorphous powder by cold pressing and subsequent isothermal forging at temperatures from 523 to 823K with the strain rate of 10-2 s-1. The porosity decreased rapidly with increasing forging temperature up to 648K, and a fully dense bulk specimen with the porosity less than 1% was achieved when the forging was carried out at and above 648K. TEM observation on the fully dense bulk alloys revealed a mixed structure consisting of nano-scaled crystalline particles and amorphous matrix. It was also revealed that the size and volume fraction of the crystalline phases increased with increasing forging temperature. Noticeably high compressive fracture strength of 1355MPa and Vickers hardness number of 530 were obtained at room temperature for the fully dense bulk specimen forged at 648K, which contains the refined crystalline particles (average size: 28nm, volume fraction: 44%) in an amorphous matrix.

NTM-01: Finite Element Study of Effects of a Non-uniform Initial Density Distribution on Powder Forging Process(NTM-I: NON TRADITIONAL MANUFACTURING PROCESS)

NTM-01: Finite Element Study of Effects of a Non-uniform Initial Density Distribution on Powder Forging Process(NTM-I: NON TRADITIONAL MANUFACTURING PROCESS)