The thixoforging of aluminium alloys has received in recent years an extensive interest for the manufacture of parts because of its advantages. To choose an aluminium alloy as raw material for a thixoforming process, it is important to know, the product characteristics, respectively the expected mechanical properties, and secondly, the semi-solid interval and the temperature of fusion. Various wrought and foundry aluminium alloys are thoroughly summarized in this review paper, together with a description of the evaluation methods for the heating temperature sensitivity. Furthermore, for thixoforging industrial applications, the heating strategy is very important, and the reheating regime should be systematically analysed. The advantages offered by thixoforging of aluminium alloys are associated to the feedstock material microstructure that results after reheating to the semi-solid range, which is key to understand the rheological behaviour and the final mechanical properties of the thixoformed parts. In the future, a process model needs to be developed to integrate microstructure conditioning during reheating of the material to the semi-solid state.

The process presented in the paper allows to produce bulk carbon fibre/thermoplastic composite parts with oriented continuous fibre to get specific mechanical loading constraints for structural parts. This fibre orientation allows to increase the mechanical strength of the composite product. This process consists of two steps: i) preforming and pre-consolidation necessary for the placement and orientation of the composite and ii) compression step. In this study, the first two steps are performed simultaneously by 3D printing. This study provides elements for optimizing certain process parameters and the associated results, particularly at different steps in the forming process. This paper also focuses on the movement of the material during shaping process. It links processing conditions and material characteristics, by determining the porosity and fibre ratio of composite part realized with different compression ratios. In addition, a repeatability study is conducted to identify the variability of the process and of the measurement method.

EPITHER is an innovative way of shaping composite materials that seek to combine the strength of continuous fibre reinforced thermoplastic (CFRT) composite materials with the high production rates existing in the forging industry. The use of composites in the manufacture of structural parts must make it possible to lighten the driving parts of vehicles and to give part of the solution to the reduction of CO2 emissions. Good material health is crucial for the production of structural parts, and some of the parameters associated with it are a direct consequence of the shaping conditions and have an influence on the strength of the final product. With a view to controlling and optimizing the shaping parameters, this study begins by defining the relevant material characteristics to be measured in order to judge the quality of the latter, then studying the links between the process and the finished product.

A comparative study of thixoforming and forging of double-cup parts in low carbon steel was performed using a combination of process in-situ experimental analysis and modeling. First, the thermal profile resulting from induction heating of the slug prior thixoforming was experimentally determined using thermocouples and compared to the results of 3D numerical simulation of induction heating. The thermal profile was found to be heterogeneous with temperature ranging from 1150 degrees C to 1425 degrees C. Numerical modeling of the thermocoupled slug demonstrated that the geometry alteration induced by thermocouples disturbs the magnetic field and thermal diffusion during induction heating resulting in a significant modification of the temperature distribution within the slug. Thermal evolution during transfer from the heating cell to the press was also monitored and the data were used to determine the heat transfer coefficient which was found to be approximately 150 W.m(-2).K-1 on a temperature range of 1300 degrees C-1400 degrees C. Numerical simulation of thixoforming and forging processes was performed using a micro-macro model and the calculated forming load evolution was compared with the in-situ experimental data collected in-situ using a force sensor located on the upper punch. The comparative study demonstrates the essential influence of the input thermal profile to carry out reliable numerical simulation. The load applied to thixoform the double-cup part was found to be 40 % lower than in forging condition whereas the extruded length resulting from thixofming is approximately 12 % higher than for the forged specimen. Post-process analysis shows that thixofomring does not affect the microstructure and tnsile propeties of the specimen in comparison with forging, except for a sligh grain coarsening of the non-extruded part of the specimen.

The innovative EPITHER process makes it possible to produce massive C/Thermoplastic composite parts with oriented continuous fibres in order to meet specific mechanical loading constraints for structural parts. This fibre orientation allows, as in the case of forging fibre pull-outs, to increase the mechanical strength of the composite product. Composite structural parts must also contribute to the reduction of CO2 emissions by reducing the weight of parts in mobile systems, particularly those in motion for power transmission. This process consists of two or three steps, the preforming necessarily for the placement and orientation of the continuous carbon fibre composites required to increase their characteristics, pre-consolidation and shaping. In this study, the first two steps are performed simultaneously by 3D printing. In order to obtain finished products with good dimensional and material characteristics. This study provides elements for optimizing certain process parameters and the associated results, particularly at different steps in the forming process. In addition, this paper focuses on the movement of the material of the parts obtained by the shaping process. It links proceeding conditions and health of the material: for example, by determining the void ratio, fibre ratio.

The present paper focuses on a new concept of evaluation of a performance index of hot forging dies through the combination of a process behaviour model and a reliability approach analysis of the forging process. The process behaviour is modelled and simulated using the computer-aided engineering FORGE® tool that allowed optimizing the forging parameters and determining the stresses and strains together with temperatures during the forging process and also identifying the factors affecting the die life. The respective reliability mechanical model is developed and reliability simulations have been conducted using PHIMECASoft tool in order to evaluate the reliability index β and determine the sensitivity of the variations in the random values of the input parameters of the forging process. The concept of this contribution has been applied to real industrial dies used to forge automotive steering levers produced in the forging workshop of the Ferrovial Company of Annaba in Algeria. The performance index is given by the number of forged parts corresponding to the reliability index of the dies before failure occurs.

For nearly two decades, researchers from academia and industry are working on the development of steel alloys thixoforging, which are not the easiest to form with this process. The early fundamental technology research demonstrated the feasibility for certain conditions. These works has focused on different steel grades, e.g. C38, M2...; different tools and their materials due to specific thermal and mechanical properties; better forming conditions; flow of the semisolid material; characteristics and the means of obtaining the semisolid state; evolution of the liquid fraction; mechanical models of deformation, process simulation, etc.Today, it is necessary to continue the development by realizing technological demonstrators integrating some industrial constraints, like production rate and costs, but it is also necessary to identify and define the field of application of this process and its limits in terms of materials, tools, cadence, forming speed, etc. The major difficulties are the interactions and the coupling of these various parameters and conditions of this forming process making it difficult to understand the mechanisms of thixoforging.In this context, a new steel grade was tested and studied. This SAE 1006 grade is deemed difficult to thixo-forge, due to its high melting point. The selected part geometries are not feasible with conventional forging. The present study reports the first results of the thixoforging of this steel for a product with specific geometric conditions and the means used and developed. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on the Technology of Plasticity.

This article presents the outcomes of using thixo-extrusion (backward and forward) to produce tubes in low-carbon steel, grade SAE1006 (C05). According to the literature data, the semisolid state of this steel, required for thixoforging, is very difficult to obtain and has never been studied for this type of shaping. The experimental tests involve using an inductive heating and a flashless forging process. This work shows the route and possibility to obtain a usable semisolid by inductive heating for thixoforging of this steel grade. It shows by simulation the validation steps before the shaping and the forming constraints. A geometrical analysis of the parts revealed the good dimensional performance of thixoforging processes with high repeatability and a good microstructure. Such thixoforged tubes extend the dimensional limits of the tube wall thickness, as compared to the case of conventional forging in one step and in the framework of a typical industrial installation. These results could be integrated into a knowledge management system of thixoforging to identify new possibility of components.

This work presents a study done on a new patented forming process, created to produce massive composite parts used for structural applications in automotive and aeronautics industries. The study presented in this paper deals with an experimental setup, used to characterize thick composite cylinders. The author presents the characterization of these cylinders and a new analysis method, in order to understand the consolidation steps of the composite in this forming process. The structural health of the part is illustrated by the analysis of the intra-bundle and inter-bundle porosities, by micrographs characterizations.

The fields of industrial applications of the thixoforging applied to steels remain to be set as more conditions as the most suitable materials, the dimensional limits, the limitations associated with tooling, the heating means, etc.To thixoforging in good conditions, the steels must have low melting temperatures and a low temperature slope to achieve complete melting that allows the use of less specific heating means.This article presents the results of thixo-extruded tubes of C05 steel grade, a low carbon steel grade. These experimental tests use flashless forging process on screw press. In this work, a geometrical parts analysis shows a good dimensional performance of thixoforging process. Another feature of thixoforging these tubes is that it pushes the dimensional limits of the thickness of the can wall compared with the case of conventional forging.

Forging in semi-solid state significantly extends the possibilities of classical hot forging. In order to fully exploit its potential, the process requires a specific and demanding environment, penalizing its industrial deployment. In this context, an alternative route is proposed. In the proposed process, semi-solid zones at the heart of the material coexist with surrounding solid zones within the part. The outcome is an optimized process where the benefits of thixoforging are reached at a significant extent within the classical process framework of hot forging. The paper investigates this proposal up to a full-scale proof-of-concept in an industrial setting.

The author presents an approach to study an innovative manufacturing process developed to produce composite parts with new geometrical possibilities. The aim of this first study is to understand the motions of fibers during the forming of this kind of composite parts and to explore the feasibility of this forming process by an experimental analysis and FEM simulations with Forge3©. The reliability of the simulation tool and its potential, never exploited in this area, will be evaluated.

The microstructure investigation and flow behavior during thixoforging of M2 steel parts were investigated. Partial remelting was performed at processing temperatures ranging from 1290°C to 1340°C corresponding to a liquid fraction range between 10% and 30% (according to differential scanning calorimetry measurements and quantitative image analyses). A conventional microstructure for thixoforming process was obtained: spherical solid grains surrounded by liquid phase. The microstructure across the heated billets was relatively homogeneous with bigger grain size near the surface. Successful thixoextrusion for producing parts was finally achieved at processing temperatures. By investigating the microstructure and load-displacement curves, different mechanisms in various forming stages were proposed.

It is necessary to well understand the microstructure evolution during high speed heating and forming for steel thixoforging, since it determines the thixotropic flow behavior of materials in the semi-solid state. A new in situ technique - high temperature Confocal Laser Scanning Microscopy (CLSM) - was developed and used for studying the microstructure evolution directly at high temperature where the microstructure in the semi-solid state could not be preserved by quenching experiments for conventional 2D characterization. Several steel grades (C38LTT, 100Cr6 and M2) were investigated during heating from the as-received state to the semi-solid state and finally cooled to the solid state).It has been found that there is a significant difference in diffusion rate of alloying elements between these grades during heating and cooling. In M2, thanks to the high content of alloying elements and their low diffusion rate, the semi-solid temperature range is greater and its microstructure in the semi-solid state could be preserved by quenching or even at a low cooling rate, which means the microstructure of M2 in the semi-solid state can be characterized in room temperature on quenched M2 samples. On the contrary, the microstructure of other steel grades 100Cr6 and C38LTT in semi-solid state can only be revealed by CLSM at high temperature because of the lower volume fraction of alloying elements and their high diffusion rate. It is very interesting to use high temperature CLSM to in situ investigate the microstructure evolution in the semi-solid state, especially at low liquid fraction.

The present paper focuses the modelling and the simulation of a direct thixoextrusion test achieved on C38 semi-solid steel. Many parameters related to thermal, mechanical, material features are involved but are currently unknown. Consequently to validate the modelling and the simulation, it is important to get various experimental informations during the test and to correlate them with simulated results. In a previous paper (Becker et al, 2008), the force-displacement curve, the temperature within the die, the macro and micro structure obtained for different process parameters during thixoextrusion of C38 were investigated. In this work, those results are correlated to those obtained by simulations of the processing. The simulations were performed using the commercial software Forge®. The thermal modelling is based on the heat equation and the thermal boundary conditions involving the heat losses, the thermal conduction within the semi-solid slug and the die and the plastic dissipation as heat source. The latent heat associated to the liquid-solid phase transformation is not considered here. The constitutive equation of the material is given by a multi-scale modelling based on micromechanics and homogenization techniques, labelled as micro-macro modelling (Favier et al, 2009). Friction is modelled using the usual modified Tresca equation. The parameters of the model are determined (i) using literature results and (ii) to match various experimental measurements obtained during the test and described in Becker et al (2008) such as the die temperature during the test and the load-displacement curve. Comparisons between experimental and simulated reveal the presence of complex temperature field and the presence of zones having very low viscosities. These zones contribute actively to the semi-solid material flow.

Today, the metallurgical industry needs to produce complex parts with high mechanical properties, low cost and high production rates.An innovative forming process, the thixoforming, is very interesting since it is possible to make some parts in fewer forming steps and with a decreased forming force.The microstructural evolution and the material flow during each step of the process must be studied to well understand the mechanisms occurring in the parts and the influence on their final mechanical properties.The objective of this work is to characterize the microstructure of a high speed tool steel grade (M2) at each step of the thixoforging process in order to better understand the influence of the process parameters and the mechanisms of deformation.As the microstructure of the material in the semi-solid state, especially the volume fraction of liquid, is very important, several 2D and 3D techniques (SEM-EDS analyses, CLSM, X-ray microtomography) have been used to characterize the microstructure, such as liquid fraction estimation, liquid phase distribution etc.The CLSM technique is used to observe the microstructure directly at high temperature, with the apparition of liquid and the solidification.It has been found that the liquid phase of M2 could be preserved even by a low cooling rate.Thus, the microstructure could be characterized on the quenched parts.By comparing the 2D SEM -EDS and 3D X-ray microtomography observations on quenched M2, the good agreement proves that both techniques are efficient in characterizing high-alloyed steels in the semi-solid state.Thixoforging experiments are finally performed in order to study the influence of the process parameters on the microstructure, final part geometry, material flow etc.After analyzing the microstructure of the thixoforged parts, some mechanisms of material flow are proposed.Moreover, by comparing the results between the thixoforging experiments and the hot forging simulations, it is found that the material flow is very different from that of hot forging process, which results from the material behavior.The latter is very sensitive to the process parameters; an accurate process control is necessary.

Process control in forging industry is essential to ensure a better quality of the product with a lower cost at the end of the manufacturing process. To control the process, a number of key parameters must be monitored to prevent product or forging plan deviations. This paper will illustrate how a variation in a process parameter can create product specifications deviations and how key parameters influence product final state. The illustration work is done on a part obtained via hot forging. An analysis is made on product parameters such as geometry, by varying the key process parameter values previously determined from a created methodology. This later is represented as a decision support system that connects product specifications (geometry, absence of defects, etc.) or other forging specifications (tool wear, involved energy...) to the process parameters. (C) 2014 The Authors. Published by Elsevier Ltd.

Semi-solid forming processes can lead to hot cracking. The process parameters responsible for hot cracking are still not well known. The paper aims at contributing to a better understanding of the process parameters promoting this phenomenon. Finite element simulations of thixoextrusion tests were carried out to analyse the thermal and mechanical fields. Comparisons between experimental and calculated results enable to propose a hot cracking criterion.

Microstructure is of crucial importance to the flow behavior of semi-solid slurries during the thixoforging process. Therefore, a thorough understanding of the microstructure evolution is required. In order to achieve this, high temperature confocal laser scanning microscopy (CLSM) and high energy X-ray microtomography were used to investigate the microstructure evolution of several steel grades (M2, 100Cr6 and C38LTT) during the heating process from as-received conditions to the semi-solid state. It was found that the microstructure development of M2 can be directly studied at high temperature via these two techniques. Two types of small carbides (MC and M6C) were present in the as-received state, while totally new interconnected carbides of specific size and composition were formed from liquid zones after cooling. It was also noted using CLSM that the diffusion rate of the alloying elements during the cooling of M2 was very low. This confirms that the volume fraction of the liquid phase of M2 at high temperature can be evaluated by three-dimensional X-ray microtomography in situ at high temperature and on quenched specimens. Contrary to M2, the microstructure of the steel grades 100Cr6 and C38LTT in the semi-solid state can only be revealed by CLSM at high temperature. All these observations are discussed in terms of microstructural development and liquid fraction during heating.