Semi-solid Forging Process Research Articles

Semi-Solid Forging Process of Aluminum Alloy Connecting Rods for the Hydrogen Internal Combustion Engine

As an important piece of equipment for hydrogen energy application, the hydrogen internal combustion engine is helpful for the realization of zero carbon emissions, where the aluminum connecting rod is one of the key core components. A semi-solid forging forming process for the 7075 aluminum alloy connecting rod is proposed in this work. The influence of process parameters, such as the forging ratio, sustaining temperature, and duration time, on the microstructures of the semi-solid blank is experimentally investigated. The macroscopic morphology, metallographic structure, and physical properties of the connecting-rod parts are analyzed. Reasonable process parameters for preparing the semi-solid blank are obtained from the experimental results. Under the reasonable parameters, the average grain size is 41.48~42.57 μm, and the average shape factor is 0.80~0.81. The yield strength and tensile strength improvement ratio of the connecting rod produced by the proposed process are 47.07% and 20.89%, respectively.

Grey-Fuzzy Logic Based Approach in Multi-Response Optimization of Semi-Solid Forging of A356 Aluminium Alloy

This paper presents an effective approach for the optimization of the semi-solid forging process of A356 Al-alloy based on the orthogonal array with the grey relational analysis and fuzzy logic analysis. Through the grey-fuzzy logic analysis, the optimization of complicated multiple performance characteristics can be converted into the optimization of a single grey-fuzzy reasoning grade. In this semi-solid forging process of A356 Al-alloy, the forging process parameters, namely the forging temperature, percent deformation, and die temperature are optimized with considerations of multiple performance characteristics including the tensile strength and hardness. The experimental results for the optimal setting have shown that the above performance characteristics in the semi-solid forging process of A356 Al-alloy can be improved effectively together through this approach.

Semi-Solid Forging of Mg Alloy AZX1311 and Mechanical Properties

This paper describes basic property in semi-solid forging method of magnesium alloy AZX1311. In the semi-solid forging process, an arbitrary fraction of solid is selected at a temperature between the liquidus and the solidus line and rapidly cooled and coagulated simultaneously with deformation of the material in a die to obtain a product. In addition, the magnesium alloy AZX1311 has excellent castability and mechanical properties. In recent years, the use of magnesium alloys for home electric appliances and automotive parts has been increasing because weight reduction can be achieved. These main manufacturing methods are casting and forging. However, these manufacturing methods have disadvantages such as large forming load and poor dimensional accuracy. Therefore, the semi-solidification forging method can improve these disadvantages. In this study, a forged semi-solid material and air cooled semi-solid material were produced using a servo press machine. Focused on impurities, porosity and microstructure. A forged semi-solid material could be produced. A semi-solid structure could be observed.

Compression deformation behavior of semisolid Al2O3np reinforced 7075 aluminum matrix composites with high solid fraction

Abstract

Tailorable Burning Behavior of Ti14 Alloy by Controlling Semi-Solid Forging Temperature.

Semi-solid processing (SSP) is a popular near-net-shape forming technology for metals, while its application is still limited in titanium alloy mainly due to its low formability. Recent works showed that SSP could effectively enhance the formability and mechanical properties of titanium alloys. The processing parameters such as temperature and forging rate/ratio, are directly correlated with the microstructure, which endow the alloy with different chemical and physical properties. Specifically, as a key structural material for the advanced aero-engine, the burn resistant performance is a crucial requirement for the burn resistant titanium alloy. Thus, this work aims to assess the burning behavior of Ti14, a kind of burn resistant alloy, as forged at different semi-solid forging temperatures. The burning characteristics of the alloy are analyzed by a series of burning tests with different burning durations, velocities, and microstructures of burned sample. The results showed that the burning process is highly dependent on the forging temperature, due to the fact that higher temperatures would result in more Ti2Cu precipitate within grain and along grain boundaries. Such a microstructure hinders the transport of oxygen in the stable burning stage through the formation of a kind of oxygen isolation Cu-enriched layer under the burn product zone. This work suggests that the burning resistance of the alloy can be effectively tuned by controlling the temperature during the semi-solid forging process.

Flow simulation and solidification phenomena of AC4CH aluminum alloy in semi-solid forging process by explicit MPS method

Semi-solid forging (SSF) is a powerful manu- facturing technology to fabricate near-net shaped products in automotiveindustries.DuringSSFprocess,thefillingbehav- ior and solidification process of AC4CH aluminum alloy is presented in this paper. The explicit MPS method program solving Navier-Stokes equation is coupled with heat transfer and solidification has been used to predict the filling pattern and temperature distribution of semi-solid material (SSM). The non-Newtonian rheological model was used as the con- stitutive equation of SSM. In this study, numerical analysis of SSF was carried out in box cavity with various flange thickness (4, 8, 12 and 16 mm) and corresponding exper- iments were undertaken for AC4CH aluminum alloy with solid fraction less than 0.5. The numerical results of SSM filling pattern and solidification phenomena in flange were validated with the experimental results. During solidifica- tion process, flow calculation was stopped and only thermal calculation was carried out. The shrinkage defect was well predicted near the lower mid area of the box cavity with flange thickness 16 mm.

Fabrication of Aluminum Bipolar Plates by Semi‐solid Forging Process and Performance Test of TiN Coated Aluminum Bipolar Plates

AbstractAluminum bipolar plates that can replace graphite bipolar plates for PEM fuel cells are made by applying a semi‐solid forging process. A semi‐solid slurry is made using electromagnetic stirring (EMS), and the resulting slurry is injected into a forging die attached to a 200 ton hydraulic press. The slurry is then compressed with a punch, flowed into a die cavity, and solidified into the bipolar plate form. A356 (cast Al alloy), A6061 (wrought Al alloy), and A1100 (pure Al) are used to make the plates. Titanium nitride (TiN) coating is deposited on the aluminum bipolar plates. An atomic force microscope (AFM) is used to measure the surface roughness of the plates. TiN coated A356 and A1100 plates have a surface roughness of Ra < 1.2 μm. The plate thickness is 1.2 mm. The active area of the channel is 70 mm × 70 mm, with a depth and width of 0.3 and 1.0 mm, respectively. The three TiN‐coated aluminum plates are combined with a unit cell for a performance test. Our results show that a current density value of 473 mA cm–2 (about 41% of the current density value of commercial graphite plates) can be obtained.

Semisolid Forging of Hypereutectic Al-Si Alloy for Automobile AC Compressor Components

Semisolid forging process, characterized by short process, near-net shape, low cost, and high performance, is increasingly playing an important role in lightweighting transportation systems for light metals. In this study, semisolid forging process for hypereutectic Al-Si alloy, as a substitute for nodular cast iron, was applied in producing automobile AC compressor components. The results showed that hypereutectic Al-Si alloy swash plate thixo-forged had higher strength than nodular cast iron one by optimizing forming process parameters.

Semisolid die forging process, microstructures and properties of AZ31 magnesium alloy mobile telephone shells

A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process, and the semisolid die forging process, microstructures, and properties of the magnesium alloy mobile telephone shell were investigated. The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press. The microstructures were observed by optical microscopy, the hardness was analyzed with a model 450SVD Vickers hardometer, the mechanical properties was measured with a CMT5105 tensile test machine, and the fractograph of elongated specimens was observed by scanning electron microscopy (SEM). The results reveal that with the increase of die forging force, the microstructures of the product become fine and dense. A lower preheating temperature and a longer dwell time are favorable to the formation of fine and dense microstructures. The optimum process conditions of preparing mobile telephone shells with excellent surface quality and microstructures are a die forging force of 2000 kN, a die preheating temperature of 250°C, and a dwell time of 240 s. After solution treatment at 430°C and aging at 220°C for 8 h, the Vickers hardness is 61.7 and the ultimate tensile strength of the product is 193 MPa. Tensile fractographs show the mixing mechanisms of quasi-cleavage fracture and ductile fracture.

DYNAMICS BEHAVIOR ANALYSIS OF GLOBULAR PARTICLE IN RHEOLOGY MATERIAL WITH CONTROLLED SOLID FRACTION

Semi-solid forging process has many advantages such as long die life, good mechanical properties and energy savings. But rheology material has complex characteristics, i.e., thixotropic behavior. Also, difference of the particle velocity between solid and liquid phase in the semi-solid state material causes a liquid segregation and specific stress variation. A number of simulation tools have been attempted for analyzing these behaviors of rheology material. However, general plastic or fluid dynamic analysis is not suitable. Therefore, we set up the stress equation to include viscosity, in order for investigating on how the moving behavior the solid particle in the rheology material during forging process is affected by viscosity, temperature, and solid fraction. In this study, a dynamics simulation was performed for the control of liquid segregation and the prediction of stresses on particles by changing forming velocity and viscosity in a compression experiment as part of a study on the analysis of the rheology aluminum forming process.

Servomechanical Press: A New Press Concept for Semisolid Forging

Semisolid forging process requires special movement of the ram, until now only achievable with hydraulic presses. The upper die, placed on the press ram, must move fast during forming of the component in order to reduce segregation phenomena, and, once the part is shaped, the die must squeeze the material so that the contraction of the material is overcome and no shrinkage defects are formed. Traditional mechanical presses are not able to reproduce this kind of cycles, only possible with hydraulic presses. The introduction of servo motors in mechanical presses makes possible the achievement of those requirements, and, therefore, the use of these presses for the semisolid forging processes. The main characteristic of this type of machines is the elimination of the flywheel and the clutch; in the solution proposed by the press builder Fagor, the AC servo motor drives the ram of the press by using a transmission based on gears and a crank. This paper presents some of the results achieved during the semisolid forging of A356 aluminium alloy using a 400 tons Fagor servo motor driven mechanical press installed at the University of Mondragon.

Microstructures and properties of semisolid billet and thixo-forging product prepared by vibrating wavelike sloping plate (VWSP) process

By using self-made vibrating wavelike sloping plate (VWSP) setup, the process of preparing semisolid billets of light alloys by semi-continuous casting and thixo-forging process were studied. Semisolid billets with fine spherical or rosette grains were prepared by the proposed process, and the solidified shell on the sloping plate surface can be effectively avoided. During the casting process, due to metal flow and vibrating, burst nucleation in the whole melt and dendrite fracture take place, which causes the formation of fine spherical microstructures. Casting temperature, vibrating amplitude, sloping plate length and sloping angle are the main factors influencing the alloy microstructure. Under the current experimental conditions, the proper casting temperature ranges of 660°C–680°C, the amplitude value smaller than 2 mm and the proper sloping angle ranges of 40°–60° are suggested. When the reheating temperature is 575°C and the holding time is 60 min for AZ91D alloy, and 597°C and 90 min for Al-6Si-2Mg (wt.%) alloy, the semisolid forging process can be successfully implemented. Thixo-forming products of such two alloys are fine with smooth appearance, good microstructures and properties.

Preparing Semisolid Light Alloys by Vibrating Wavelike Sloping Plate Process and Thixoforming

By using self-made vibrating wavelike sloping plate setup, semisolid billets with fine spherical or rosette grains have be prepared by semi-continuous casting, and the solidified shell on the sloping plate surface can be effectively avoided. Burst nucleation in the whole melt and dendrite fracture causes the formation of fine spherical microstructures. Under the current experimental conditions, proper casting temperature ranges of 660°C~680°C and the amplitude value of under 2mm proper are suggested. When the reheating temperature is 575°C and the holding time is 60min for AZ91D alloy, 597°C and 90min for Al-6Si-2Mg (wt-%) alloy, semisolid forging process can be successfully implemented. Thixo-forming products of two alloys are fine with smooth appearance, good microstructures and properties.

Investigation of Flow Behaviour and Microstructure on X210CrW12 Steel in Semi-Solid State

This paper describes the basic investigation on material behaviour of cold working steel X210CrW12 in semi-solid state concerning the semi-solid forging. It includes a study of flow behaviour and microstructure by means of a high temperature isothermal upsetting test applying a special cylinder sample with a shell, which is designed to avoid collapsing of samples during the compression. The flow curve of the semi-solid steel is determined by an inverse modelling via FEM using the obtained load curve of the samples and the separately obtained flow stress of the shell material. An extensive microstructure study of the compressed samples provides a comprehensive understanding on the flow mechanism of the semi-solid steel. At the end of the paper some general restrictions and remarks for the semi-solid forging process are given based on the gained results.

The effect of gate shape on the filling limitation in the semi-solid forging process and the mechanical properties of the products

To obtain high quality components with the semi-solid forging process, it is important to obtain a homogeneous distribution of solid particles without liquid segregation. In the closed-die semi-solid forging process, liquid segregation is strongly affected by injection velocity than process parameters such as the pressure and the solid fraction, because the material has to travel a relatively long distance to fill the cavity through a narrow gate before solidification begins. To investigate the effect of gate shape on the filling phenomenon in the semi-solid forging process, two kinds of gate shape system are proposed. A filling test for the two kinds of gate systems was carried out. Therefore, in this study, the optimal injection velocity and die temperature were investigated to fabricate a near-net-shape compressor component called an Al frame. For uniformity of the solid particles, the injection velocity has to be higher than 160 and 370 mm/s to produce sound part without filling defects, in the range of die temperature of from 200 to 300 °C. In addition, the mechanical properties for a forged semi-solid component with a good filling situation were tested with the specimen before and after heat treatment. The forming limits and mechanical properties were discussed in terms of chemical composition and microstructure of the materials used.

The influence of induction heating on the microstructure of A356 for semi-solid forging

Abstract Semi-solid forging is a compound forging technology to develop conventional forging process. Among the several steps of the semi-solid forging process, the heating step of the billet prior to semi-solid forging step is necessarily required to obtain a globular microstructure. For the forming operation to work properly, it is important to heat the billet uniformly for the uniformity of solid–liquid distribution and globular grain. It is also required to heat the billet as soon as possible. To satisfy these requirements, induction heating has been generally used for a long time. This paper presents a method to find the heating condition and the temperature distribution inside the billet with induction heating apparatus by comparing computer simulation with experiment for A356. The microstructure of the billet is also investigated by using a conventional parameter, i.e. the mean size of globules, in connection with the heating condition.

Finite element analysis of compression holding step in semi-solid forging and experimental confirmation

The technology of semi-solid forging (SSF) has been actively developed to fabricate near-net-shape products using light and difficult to form materials. Generally, the SSF process is composed of slug heating, forming, compression holding and an ejecting step. After the forming step in SSF, the slug is compressed during a certain holding time in order to completely fill the die cavity and to accelerate the solidification rate. The compression holding time that can affect microstructural characteristics, mechanical properties and the shape of products is important. This paper presents a procedure to predict the compression holding time for obtaining the final shape of the product. Information is preheated temperature and the solid fraction for a cylindrical slug in the compression holding step of a closed-die compression process using heat transfer analysis and considering latent heat, by means of the finite element method. The influence of the predicted compression holding time on microstructural characteristics, mechanical properties and shape of the product is investigated by experiment.

The effect of forging process conditions of semi-solid aluminum material on mechanical properties

Semi-solid forging(SSF) process of A356 aluminium alloy has been studied to assess the effect of process variables on the component integrity. Semi-solid material(SSM) was fabricated by mechanical and electro-magnetic stirring process. The fabricated SSM by using mechanical stirring process has been carried out on cooling rate of 0.022.deg. C/sec 0.0094.deg. C/sec and stirring speed n=600, 1000 rpm, respectively. The fabricated SSM by using electro-magnetic stirring process is supplied by Pechiney. The holding time and temperature in the semi-solid state before forging also affects the globular microstructure of alloy. Therefore, the influence of these two parameters is discussed in terms of the microstructure of alloy. The SSF process has been conducted with three different die temperatures(=250.deg. C, 300.deg. C, 350.deg. C) and two kinds of gate types(straight gate and orifice gate). This paper is to investigate the influence of gate shapes of die on filling phenomena in SSF process more deeply. The mechanical properties of forged components were also investigated for variation of process conditions such as die temperature, gate shape and SSM.