Rheological Behaviour and Microstructural Evolution of Semi-Solid A356 Alloy Produced by Different Routes

2006 ◽  
Vol 116-117 ◽  
pp. 565-568
Author(s):  
Eugênio José Zoqui ◽  
Marcelo Paes ◽  
Maria Helena Robert
Keyword(s):  
Raw Materials ◽  
A356 Alloy ◽  
Rheological Behaviour ◽  
Raw Material ◽  
Structure Evolution ◽  
Geometrical Factor ◽  
Compression Tests ◽  
Production Route ◽  
Semi Solid ◽  
Solid Alloys

Different techniques used to produce semi-solid alloys can result in different structures in the material and, therefore, in distinct rheological behaviours which determine its thixo-forming ability. Suitable raw materials to be used for SSM forming must present non-dendritic, very fine or fragmented structure in order to globularize without excessive agglomeration when re-heated to the semi-solid state. This work analyses the influence of raw material production route on the rheological behaviour of semi-solid A356 alloy. Techniques used were: electromagnetic stirring (EMS) and chemical ultra-refining (UR). Samples were re-heated to 580oC (~ 0.45 solid fraction) and hold for 0, 90 and 210s to allow the observation of the structure evolution. After structures characterization, the samples were submitted to compression tests, at δH/δt = 10mm/s, in the same temperature/holding time conditions. Viscosity of the differently prepared raw material was related to the grain size, primary particle size, geometrical factor (roundness shape factor and contiguity).

Evaluation of Al-5wt%Si-5wt%Zn as Raw Material for Semisolid Forming

2019 ◽  
Vol 285 ◽  
pp. 339-344 ◽  
Author(s):  
Cecilia Tereza Weishaupt Proni ◽  
Leandro Cássio de Paula ◽  
Luis Vanderlei Torres ◽  
Eugênio José Zoqui
Keyword(s):  
Raw Materials ◽  
Liquid Fraction ◽  
Rheological Behaviour ◽  
Simulation Software ◽  
Raw Material ◽  
Compression Tests ◽  
Temperature Range ◽  
Liquid Transition ◽  
Semisolid Forming ◽  
Zn Alloy

Designing new alloys for semisolid processing is key to the success of semisolid materials technology. While aluminium-silicon and aluminium-zinc alloys have been tested as potential raw materials, ternary aluminium alloys containing silicon and zinc have yet to be tested. As such alloys may exhibit the rheological behaviour required for semisolid forming and the excellent final mechanical properties of Al-Zn alloys, we investigated the thermodynamic aspects of the solid-liquid transition of Al-5.5wt%Si-5wt%Zn alloy, the morphological stability of this alloy in the semisolid temperature range and the corresponding rheological behaviour. Thermo-Calc® simulation software was used to evaluate the solid-to-liquid transition and identify the semisolid temperature range within which the liquid-fraction sensitivity is low and the process is therefore controllable. Based on the results of the simulation, a target temperature of 588 °C was chosen. This is sufficient to produce a liquid fraction of 55 % and a corresponding liquid-fraction sensitivity (dfl/dT) of 0.009 C-1. The Al-5wt%Si-5wt%Zn alloy was prepared by conventional casting in a refrigerated copper mould without grain refining, and the alloy was characterized to determine the stability of the microstructure after heating to 588 °C and holding at this temperature for holding times of 0, 30, 60, 90 and 120 s. The same temperature and holding times were used to evaluate the rheological behaviour in hot compression tests. A grain size of 170 μm, globule size of 100 μm and circularity of 0.6 were achieved, leading to a maximum apparent viscosity of 2 x 105 Pa.s, which rapidly decreased to 3 x 104 Pa.s after a shear rate of 9 s-1 was reached.

scholarly journals On a Class of Thermo-Visco-Plastic Constitutive Equations for Semi-Solid Alloys

2008 ◽  
Vol 141-143 ◽  
pp. 653-658 ◽  
Author(s):  
Stefan Benke ◽  
G. Laschet
Keyword(s):  
A356 Alloy ◽  
Material Model ◽  
Viscoplastic Material ◽  
Micro Structure ◽  
Material Models ◽  
Equiaxed Solidification ◽  
Coherency Temperature ◽  
Yield Functions ◽  
Semi Solid ◽  
Solid Alloys

The behavior of semi-solid alloys is quite different in tension, compression and shear and depends strongly on the morphology of the micro-structure. This article outlines a generalized viscoplastic material model for semi-solid alloys which reflects this complex viscoplastic behavior. From the generalized model a number of well known yield functions and viscoplastic material models for semi-solid and solid materials can be reproduces. The general model is applied to describe the behavior of the semi-solid A356 alloy below the coherency temperature during equiaxed solidification.

Optimal Filling of Test Dies for Evaluating Properties of Semi-Solid Alloys

2006 ◽  
Vol 116-117 ◽  
pp. 145-148
Author(s):  
Chee Ang Loong ◽  
Chang Qing Zheng
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
A356 Alloy ◽  
Flow Patterns ◽  
Optical And Electron Microscopy ◽  
Semi Solid ◽  
The Moment ◽  
Alloy Segregation ◽  
Solid Alloys ◽  
Filling And Solidification

An investigative study was conducted on how two different dies designed to produce sound specimens for evaluating mechanical properties of semi-solid alloys could be filled optimally. The first die contains one cavity that produces a wedge with a sectional thickness varying from 19.05 mm (0.75 in) to 9.52 mm (0.375 in). The second die contains four cavities fed by a single runner, producing ASTM-type round bars with a diameter of 9.52 mm (0.375 in). Experiments were undertaken to cast partial and complete shots of A356 alloy test specimens under controlled injection conditions. Flow patterns developed from the moment the alloy entered the cavity were noted, including difficulties experienced in balancing flow in the four-cavity die. Microstructural abnormalities were observed in the bar specimens examined using optical and electron microscopy. It was found that control of filling and solidification in the wedge die was much easier and specimens produced did not result in any significant alloy segregation.

Influence of Carbon Nanotubes on Traditional Material

2021 ◽  
Vol 1023 ◽  
pp. 147-154
Author(s):  
Berenice Zúñiga-Torres ◽  
Francisco Hernández-Olivares ◽  
Francisco Fernandez-Martinez ◽  
Alonso Zúñiga-Suárez ◽  
Brad Emilio Noboa Ruiz
Keyword(s):  
Carbon Nanotubes ◽  
Raw Materials ◽  
Aqueous Media ◽  
Raw Material ◽  
Compression Tests ◽  
Griffith Criterion ◽  
Soil Cement ◽  
Simple Compression ◽  
Validation Of Results

Brick as a material is of vital importance in the construction industry, however, the burning processes for its preparation contribute to environmental pollution and the generation of greenhouse gases; for this reason, the present research has as aims to propose quality traditional materials for sustainable buildings through the design of soil-cement mixtures in making brick using raw materials from the amazon region of Ecuador: Centza mine (MC) and Quiringue mine (MQ) and improve the mechanical properties of the brick by incorporating carbon nanotubes, which have been dispersed in two aqueous media, sodium naphthalene sulfonate (NSS) and calcium chloride (CC) in percentages of 0.5%, 1% and 1.5%. The characterization of the raw material (analysis: physicochemical and mineralogical) was of great help. The optimum percentage of cement and water was determined through simple compression tests and soil compaction respectively. The different combinations were tested at indirect traction strength at ages 7, 14 and 28 days, determining an optimal mixture for each group of combinations, in this way the simple compressive strength of bricks has been estimated using the Griffith criterion and validation of results by finite element method applying the CivilFEM software, obtaining a resistance of 4 MPa in mixtures of SC-Ar1, 6.3 MPa in combinations of MWCNTs NSS-9 and 5.3 MPa in mixtures of CC-4 MWCNTs, increasing resistance by 57.5% and 32.5% with respect to soil-cement bricks and qualifying them as suitable for use in construction according to standars.

scholarly journals Effect of Moisture on the Behaviour of an Extruded Clay Paste

2013 ◽  
Vol 554-557 ◽  
pp. 2230-2236
Author(s):  
Jérémie Vignes ◽  
Fabrice Schmidt ◽  
Gilles Dusserre ◽  
Jean Frédéric Dalmasso
Keyword(s):  
Inverse Analysis ◽  
Linear Models ◽  
Raw Materials ◽  
Industrial Process ◽  
Rheological Behaviour ◽  
Rheological Parameters ◽  
Compression Tests ◽  
State Of Stress ◽  
Constitutive Parameters ◽  
Force Displacement

In the industrial process, the moisture of the clay sheet obtained by extrusion and pressed to form a tile varies in time. It depends on the nature and the mixing of the raw materials during the production. In order to model and undersand the influence of the moisture on the pressing step, it is necessary to determine the parameters of the rheological and tribological laws. A study of the rheological behaviour, based on free compression tests on cylinder samples, allowed to use an elasto-visco-plastic behaviour for the extruded clay paste. The different constitutive parameters were estimated by an inverse analysis based on the experimental force/displacement curves. The identification was performed with the optimisation algorithm implemented in the commercial software Forge® 2009. The influence of the water content in the paste on the rheological parameters was identified and fitted using linear models. The friction factor was measured from tests on a rectilign tribometer. To understand the influence of the moisture, we simulated a compression test, using Forge® involving the shaping of a tile lug. This geometry is representative of the state of stress during the pressing of the tile, in an area currently sujected to defects. The numerical model show that an increase of eighteen percent of the moisture allows to decrease by half the pressing force.

Characterization of the Microstructure and Rheological Behavior of Al-4wt%Si-2.5wt%Cu Alloy Produced by Direct Chill Casting and Electromagnetic Stirring

2012 ◽  
Vol 192-193 ◽  
pp. 142-148 ◽  
Author(s):  
Luis Vanderlei Torres ◽  
Eugênio José Zoqui
Keyword(s):  
Rheological Behavior ◽  
Apparent Viscosity ◽  
Primary Particle ◽  
Raw Materials ◽  
Morphological Evolution ◽  
Raw Material ◽  
Electromagnetic Stirring ◽  
Cu Alloy ◽  
Semi Solid

This work involved an evaluation of a Al-4wt%Si-2.5wtCu alloy to be used as raw materials in the thixoforming process. The alloy was produced by direct casting under electromagnetic stirring to obtain ingots of 250 mm length and 30 mm diameter. The alloy was analyzed to determine their morphology and rheological behavior in the semi-solid range. The tests included characterization of the microstructural evolution by subjecting them to re-heating treatment in two conditions of solid fractions, 45% and 60%, for 0, 30, 90 and 210 s. A compression testing device designed specifically to evaluate semi-solid materials was used to determine the rheological behavior, and the tests were performed at the same heating rate and hold times to determine the apparent viscosity. The use of electromagnetic stirring to produce the raw material was effective in producing alloy with very small grain/primary particle sizes (80 up to 120 µm). Based on the morphological evolution in the semi-solid state, the alloy showed only minor variations in grain/primary particle size and surface factor (SF) as a function of the different globularization heat treatment times, suggesting that all these alloys are suitable for production. The Al-4.0wt%Si-2.5wt%Cu alloy with 45% solid fraction presented apparent viscosity about 1.5 x106 Pa.s.

scholarly journals Production of spherical titanium alloy powders used in additive manufacturing from titanium scrap

2020 ◽  
Vol 321 ◽  
pp. 07008
Author(s):  
Taras Yanko ◽  
Viktor Brener ◽  
Olexandr Ovchinnikov
Keyword(s):  
Titanium Alloy ◽  
3D Printing ◽  
Raw Materials ◽  
Raw Material ◽  
Chemical Compositions ◽  
Metal Powders ◽  
Hydrogen Recovery ◽  
Production Route ◽  
Actual Yield ◽  
Technical Solutions

The main materials for 3D printing of titanium are fine metal alloy powders from which produce final articles with required quality. These powders must have definite chemical compositions, physical/mechanical characteristics, and also necessary operational properties. Key parameters of titanium alloy powders are homogeneity of chemical compositions, microstructures as well as flow ability. Conventional atomisation methods for metal powders like GA, PREP, PA, etc, are complicated and sufficiently expensive. Alternative production route is usage of complex processing technology of titanium alloy scrap as initial raw material. Spheriodised powder manufacturing scheme which includes raw material preparation, preliminary and final treatments have been presented. At the first step titanium scrap was divided according to titanium alloy types, purified from contaminants and oxide films. Then prepared materials were converted to non-spherical powders with definite fractional compositions using hydrogenation/de-hydrogenation (HDH) method. Experimental HDH equipment allows close cycle of hydrogen recovery almost without losses. Obtained non-spherical powders were treated in the plasma unit yielding spherical titanium alloy. Offered technical solutions permit production of raw materials for 3D printing from scrap with high actual yield of required fractional compositions.

Microstructure of Thixoformable Hypoeutectic Cast Iron

2012 ◽  
Vol 192-193 ◽  
pp. 219-224 ◽  
Author(s):  
Eugênio José Zoqui ◽  
Angel Sanchez Roca ◽  
Hipólito Domingo Carvajal Fals
Keyword(s):  
Cast Iron ◽  
Morphological Evolution ◽  
Raw Material ◽  
Heating Process ◽  
Compression Tests ◽  
Silicon Alloys ◽  
Aluminum Silicon Alloys ◽  
Final Microstructure ◽  
Semi Solid ◽  
Aluminum Silicon

The use of a specially designed hypoeutectic cast iron as a potential raw material for the thixoforming process is described in this paper. Thixoforming technology normally uses aluminum-silicon alloys such A356 and A357 as raw materials. Iron-based alloys are less common, despite the lower cost of the raw material. The paper describes the semi-solid behavior and corresponding final microstructure of a hypoeutectic gray cast iron after thixoforming tests. The Fe-2.6wt%C-1.5wt%Si alloy was prepared via conventional casting in sand molds. Samples were heated to the semi-solid state at 1160 and 1180oC and held at these temperatures for 0, 30, 90 and 120s, and then subjected to compression tests. Two-platen compression tests were carried out in an instrumented eccentric press in order to determine the semi-solid behavior. The holding time in the semi-solid range simulates the industrial heating process that is time-controlled rather than temperature-controlled. The semi-solid behavior indicated that the semi-solid cast iron behaves like aluminum-silicon alloys, presenting a stress of up to 24MPa under 80% strain and a corresponding apparent viscosity of up to 1.5*105 Pa.s at 1180oC. The final microstructure after compression testing was essential in determining the material’s morphological evolution. Tests revealed that heating up to the semi-solid range followed by thixoforming changes the material’s graphite morphology from type A to B (or E), but does not significantly affect the interdendritic arm spacing between graphite lamellae. The resulting structure is composed of fine graphite and pearlite.

Sign in / Sign up

Export Citation Format

Share Document