Experimental Investigations and Computer Simulation of the Liquid Fraction Evolution during the Solidification of Alloys Suitable for Semi-Solid Processing

2004 ◽  
Vol 75 (1) ◽  
pp. 13-19 ◽  
Author(s):  
Evgueni Balitchev ◽  
Heike Meuser ◽  
Dieter Neuschütz ◽  
Wolfgang Bleck
Keyword(s):  
Computer Simulation ◽  
Liquid Fraction ◽  
Experimental Investigations ◽  
Semi Solid

A Computer Simulation Approach for Engineering Air-Jet Spun Yarns

1997 ◽  
Vol 67 (3) ◽  
pp. 223-230 ◽  
Author(s):  
Rangaswamy Rajamanickam ◽  
Steven M. Hansen ◽  
Sundaresan Jayaraman
Keyword(s):  
Computer Simulation ◽  
Computer Simulations ◽  
Fiber Length ◽  
Experimental Investigations ◽  
Simulation Approach ◽  
Air Jet ◽  
Fiber Fineness ◽  
Spun Yarns ◽  
Yarn Count ◽  
Wrap Angle

A computer simulation approach for engineering air-jet spun yarns is proposed, and the advantages of computer simulations over experimental investigations and stand-alone mathematical models are discussed. Interactions of the following factors in air-jet spun yarns are analyzed using computer simulations: yarn count and fiber fineness, fiber tenacity and fiber friction, fiber length and fiber friction, and number of wrapper fibers and wrap angle. Based on the results of these simulations, yarn engineering approaches to optimize strength are suggested.

Experimental Investigations And Numerical Modelling of 210CR12 Steel in Semi-Solid State

2011 ◽  
Author(s):  
Piotr Macioł ◽  
Władysław Zalecki ◽  
Roman Kuziak ◽  
Aleksandra Jakubowicz ◽  
Stanisław Węglarczyk
Keyword(s):  
Solid State ◽  
Numerical Modelling ◽  
Experimental Investigations ◽  
Semi Solid

Steel Grades Adapted to the Thixoforging Process: Metallurgical Structures and Mechanical Properties

2006 ◽  
Vol 116-117 ◽  
pp. 712-716 ◽  
Author(s):  
Marc Robelet ◽  
Ahmed Rassili ◽  
Dirk Fischer
Keyword(s):  
Mechanical Properties ◽  
Liquid Fraction ◽  
Solidus Temperature ◽  
Process Temperature ◽  
Heating Process ◽  
Work Piece ◽  
Inductive Heating ◽  
Steel Grades ◽  
Automotive Part ◽  
Semi Solid

Thixoforming of steel offers the advantages of casting technology in combination with high mechanical strength that can only be achieved by forging. The progress in establishing this technology in industry depends on the success in the development of suitable steel grades. Recent investigations dealt with the development of steel grades that are especially adapted to the thixoforming process. For this, alloys were developed with a lower solidus temperature and a wider process temperature range compared to classic forging steels. In consequence, the inductive heating process is more tolerant to inaccuracies and for a given liquid fraction the process temperature window is easier to handle. It is desired to obtain great degrees of deformation at rather low forming forces as these parameters determine the size of the needed presses. This behaviour is affected by the present liquid fraction in the slug and the heat transfer between work piece and die. It was detected that variations of the forming force have a direct influence on the quality of the thixoformed parts. In order to make the thixoforming technology of steels competitive versus other forming technologies, the parts must show a favourable microstructure and thus, good in-use properties. In this paper various solutions are compared. The main results obtained in the optimization research, namely, the steel grades adapted to semi-solid forming, the resulting process parameters and the mechanical properties of thixoforming parts will be presented for two exemplary steel grades. By producing a real automotive part, thixoforging of steels with regard to the adapted materials and to the ongoing industrial implementation of this process is proved.

Microstructure Evolution and Coarsening Mechanism of 7075 Semi-Solid Aluminum Alloy Pre-Deformed by ECAP Method

2016 ◽  
Vol 256 ◽  
pp. 294-300 ◽  
Author(s):  
Jin Long Fu ◽  
Yu Wei Wang ◽  
Kai Kun Wang ◽  
Xiao Wei Li
Keyword(s):  
Aluminum Alloy ◽  
Solid State ◽  
Ostwald Ripening ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Semi Solid ◽  
Equiaxed Grains ◽  
Kinetics Of

To investigate the influence of refined grains on the microstructure of 7075 aluminum alloy in semi-solid state, a new strain induced melting activation (SIMA) method was put forward containing two main stages: pre-deformation with equal channel angular pressing (ECAP) method and isothermally holding in the semi-solid temperature range. The breaking up and growth mechanisms of the grains and kinetics of equiaxed grains coarsening during the semi-solid holding were investigated. The results showed that the average grain size after ECAP extrusion decreased significantly, e.g., microstructure with average globular diameter less than 5μm was achieved after four-pass ECAP extrusion. Obvious grain coarsening had been found during isothermal holding in the semi-solid state and the roundness of the grains increased with the increasing holding time. The proper microstructure of 66.8μm in diameter and 1.22 in shape factor was obtained under proper soaking condition (at 590°C for 15 min). Two coarsening mechanisms, namely, coalescence in lower liquid fraction and Ostwald ripening in higher liquid fraction contributed to the grain growth process.

Semi-Solid Casting of Pure Magnesium

2019 ◽  
Vol 285 ◽  
pp. 464-469 ◽  
Author(s):  
Ulyate Andries Curle ◽  
Jeremias D. Wilkins
Keyword(s):  
Temperature Interval ◽  
Liquid Fraction ◽  
Thermodynamic Temperature ◽  
Casting Process ◽  
Pure Magnesium ◽  
Time Interval ◽  
Thermal Arrest ◽  
Solidification Temperature ◽  
Semi Solid ◽  
Solid Liquid

Semi-solid processing works on the principal of a solidification temperature interval of a substance. The substance is heated to a temperature within this interval so that there exists a related solid-liquid fraction ratio. The substance with this phase structure is then shaped by a forging or casting process. It has been stated before that it is impossible to semi-solid process and cast pure metals or eutectic alloys due to their thermodynamic temperature invariance, meaning that there is no temperature interval. It was demonstrated recently that it is possible to semi-solid casting high purity aluminium (Curle UA, Möller H, Wilkins JD. Scripta Materialia 64 (2011) 479-482) and the Al-Si binary eutectic (Curle UA, Möller H, Wilkins JD. Materials Letters 65 (2011) 1469-1472). The working principal is that there exists a time interval during thermal arrest during which solidification takes place with a solid-liquid fraction ratio until all the liquid is consumed upon cooling. The aim with this work is to demonstrate that pure magnesium can also be rheo-high pressure die cast (R-HPDC) with the system developed at the CSIR in South Africa. Magnesium is notoriously difficult to cast due to the thermal properties of magnesium. The metal was poured into a cup, processed for about 6 seconds after which it was HPDC into a plate. The microstructure of the casting consists of a structure that was solid and a structure that was liquid during thermal arrest at the time of casting.

Inductive Reheating of Steel Billets into the Semi-Solid State Based on Pyrometer Measurements

2006 ◽  
Vol 116-117 ◽  
pp. 734-737 ◽  
Author(s):  
Alexander Schönbohm ◽  
Rainer Gasper ◽  
Dirk Abel
Keyword(s):  
Solid State ◽  
Measurement Errors ◽  
Liquid Fraction ◽  
Solidus Temperature ◽  
Measurement Data ◽  
Heating Process ◽  
Production Environment ◽  
Loop Control ◽  
Control Scheme ◽  
Semi Solid

The aim of the paper is to demonstrate a control scheme by which it is possible to reproducibly reheat steel billets into the semi-solid state. Usually a heating program is used to reheat the billet into the semi-solid state. Our experiments showed that this control scheme leads to varying semi-solid fractions from one experiment to the next. To gain information about the billet’s state its temperature is often used since there is a known relationship between the temperature and the liquid fraction. Direct measurement of the temperature via thermocouples is not feasible in a production environment, therefore a radiation pyrometer has been used as a contact-less measurement device. The accuracy of the pyrometer depends heavily on the exact knowledge of the radiation coefficient, which can vary from billet to billet due to different surface properties and which is subject to change during the heating process. These uncertainties prohibit the implementation of a closed-loop control scheme since the exact temperature cannot be measured with the required accuracy. In order to be independent of the measurement errors the proposed control scheme only relies on the slope of the temperature. By detecting the distinct change of slope which occurs when the solidus temperature is crossed, the beginning of the melting process can be determined. The energy fed to the billet from this point onward determines the resulting liquid fraction. By detecting the entry into the solidusliquidus interval and then feeding the same amount of energy to each billet, it is guaranteed that the billet reaches the desired liquid fraction even by uncertain absolute value of the temperature and by small variations of the alloy composition. For the experiments the steel alloy X210 has been used and measurement data demonstrate the feasibility of the proposed control scheme.

Net-Shape Forming of a Roof Joint Node by Thixoforming of A357 Aluminum Alloy for a Low Speed Electric Vehicle

2013 ◽  
Vol 774-776 ◽  
pp. 1145-1148
Author(s):  
Sang Yong Lee
Keyword(s):  
Electric Vehicle ◽  
Heating Temperature ◽  
Liquid Fraction ◽  
Frame Structure ◽  
A357 Alloy ◽  
Low Speed ◽  
Injection Speed ◽  
A357 Aluminum Alloy ◽  
Net Shape Forming ◽  
Semi Solid

In the present study, process developments for net-shape forming of aluminum roof joint node have been described. These joint node parts were designed for low speed electric vehicles of which operating condition is more moderate than general compact cars. Thixoforming of Al-7%Si-0.5%Mg (A357) alloy has been applied to the net-shape forming of a complex roof joint node to support aluminum space frame structure of low speed electric vehicle. Optimum heating temperature for the A357 billet was between 580 and 585°C corresponding to the semi-solid temperatures showing 20-30% of liquid fraction. An injection speed of around 100mm/s and preheating of die at temperatures of 200~250°C were also necessary conditions to obtain reasonable thixoformed parts.

A Study of Microstructure Properties of AISI D2 Tool Steel in Partial Re-Melting Method

2014 ◽  
Vol 699 ◽  
pp. 76-80 ◽  
Author(s):  
M.N. Mohammed ◽  
M.Z. Omar ◽  
J. Syarif ◽  
Z. Sajuri ◽  
M.S. Salleh ◽  
...  
Keyword(s):  
Tool Steel ◽  
Liquid Fraction ◽  
Cold Work ◽  
Industrial Applications ◽  
Melting Method ◽  
Shaping Process ◽  
Aisi D2 ◽  
Semi Solid ◽  
Net Shaping ◽  
Aisi D2 Tool Steel

Due to the growing demand for cold-work tool steel in various industrial applications, it is crucial to improve the fabrication technique, because complex shapes involve an extensive and costly workshop effort. Hence, a one-step net-shaping process, such as the semi-solid forming, could offer great benefits. With the aim of finding a minimum process chain for the manufacturing of a high-quality production, the microstructural evolution of the ledeburitic AISI D2 tool steel in the semi-solid-state was studied experimentally via the Direct Partial Re-Melting Method (DPRM). Samples were heated in an argon atmosphere up to 1255°C, which corresponded to about 16% of liquid fraction, and held for 0 minute. The microstructural observation after DPRM showed that the equiaxed austenite grains are observable within a small liquid matrix. The microstructure also contains primary, non-dissolved carbides with a new, precipitated eutectic.

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