Evaluation of Strip Rolling Directly from the Semi-Solid State

The aim of this work is to study the solidification conditions necessary to produce good quality/low defect metal alloy strip when thixorolling directly from the semi-solid state. To facilitate the study lead/tin alloys were chosen for their relatively low operating temperature. The objective is to extrapolate these findings to the higher temperature aluminium alloys. Three alloys (70%Pb- 30%Sn, 60%Pb-40%Sn, 50%Pb-50%wtSn) were used particularly to study the influence of the solidification interval. The equipment consists of a two roll mill arranged as an upper and lower roller, where both rollers are driven at a controlled speed. The lower roller is fed with semi solid alloy through a ceramic nozzle attached to the lower end of a cooling slope. Several types of nozzle and their position at the roller were tested. This produced different solidifications and consequently different finished strip. The alloys were first cast and then poured onto the cooling slope through a tundish in order to create a continuous laminar flow of slurry and uniformity of metal strip quality. The pouring was tested at different positions along the slope. The cooling slope was coated with colloidal graphite to promote a smooth slurry flow and avoid the problem of adherence and premature solidification. The metallic slurry not only cools along the slope but is also initially super-cooled to a mush by the lower roller whilst at room temperatures, thus enabling thixorolling. It was also found that the nozzle position could be adjusted to enable the upper roller to also contribute to the solidification of the metallic slurry. However the rollers and the cooling slope naturally heat up. Temperature distribution in these zones was analysed by means of three thermocouples positioned along the cooling slope and a fourth in the base of the semi solid pool within the nozzle. The objective being to design an optimum pouring and cooling system. The formed strip was cooled down to room temperature with a shower of water. Microstructures of the thixorolling process were analysed. The differences in solidification conditions resulted in differing qualities of finished strip and corresponding defect types, all of which are a serious quality issue for the rolled product.

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Evaluation of Strip Rolling Directly from the Semi-Solid State

Solid State Phenomena - Semi-Solid Processing of Alloys and Composites ◽

10.4028/3-908451-26-4.433 ◽

2006 ◽

pp. 433-436

Author(s):

Antonio de Pádua Lima Filho ◽

Márcio Iuji Yamasaki

Keyword(s):

Solid State ◽

Strip Rolling ◽

Semi Solid

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Influence of Morphology on the Rheological Behavior of Semi-Solid A356 Aluminum Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.116-117.601 ◽

2006 ◽

Vol 116-117 ◽

pp. 601-605

Author(s):

Heng Hua Zhang ◽

Xian Nian Zhang ◽

Guang Jie Shao ◽

Luo Ping Xu ◽

Yi Tao Yang ◽

...

Keyword(s):

Aluminum Alloy ◽

Solid State ◽

Rheological Behavior ◽

Apparent Viscosity ◽

Flow Behavior ◽

A356 Alloy ◽

Solid Alloy ◽

A356 Aluminum Alloy ◽

A356 Aluminum ◽

Semi Solid

The morphology of semi-solid alloy is one of the key influence factors on the rheological behavior of slurry during die filling and the mechanical properties of formed parts. However, it is difficult to study such effect due to hard controlling of morphology in semi-solid state. In this paper, a self-developed Searle-type viscometer was used to determine the rheological behavior of A356 aluminum alloy in different morphology, which was refined with the salts mixture of K2TiF6 and KBF4. The results indicated that the flow behavior of refined A356 alloy in the semi-solid state possesses obviously thixotropic behavior under isothermal shearing condition with less time to reach steady state and lower steady apparent viscosity as compared to that of the A356 alloy. During continuous cooling at a constant shearing rate, the apparent viscosity of refined A356 slurry in the same solid fraction decreased with the content of Ti. It is shown from quantitative image analysis that the primary α-Al grain in the refined alloy evolves from dendrites to rosettes or sphericitys, and then tends to be rounder and finer in higher Ti content. The mechanism of the influence of morphology on rheological behavior was also discussed in this paper.

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Simplified Rheocasting of Al-Si Alloys Sheared by Mechanical Stirring

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.651-653.1545 ◽

2015 ◽

Vol 651-653 ◽

pp. 1545-1550 ◽

Cited By ~ 2

Author(s):

Alfredo Hernández ◽

J. Federico Chávez ◽

Raquel E. Hernández

Keyword(s):

Stainless Steel ◽

Solid State ◽

Shear Rate ◽

Microstructural Characterization ◽

Dendritic Morphology ◽

Solid Alloy ◽

Mechanical Stirring ◽

Simplified Method ◽

Thixotropic Behavior ◽

Semi Solid

A rheocasting prototype for the semi-solid processing of Al-Si alloys was designed and assembled at laboratory scale, this is the first attempt for the development of S2P equipment in Mexico. This work describes the simplified method of mechanical stirring and the calculation of the theoretical parameters for the operation of the experimental device in order to provide shear rate into the slurry by a stainless steel impeller inside a crucible made of hot work steel. Moreover, a vertical pressure die-rheocasting system it is applied with the semi-solid alloy flowing counter the position of the injector during the displacement of the crucible in order to fill the mold. New design is applied in this rheocasting equipment.The semi-solid state with thixotropic behavior is produced in the stirred AlSi7Mg alloy; this condition allows the non-dendritic morphology because the intensively stirring at the beginning of the solidification produces the trimming of dendrites, growing so the primary solid (α) in globular shape surrounded by eutectic microstructure. Preliminary microstructural characterization was performed.

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Effect of angle, length and circulation cooling system on microstructure A360 Aluminum alloy in semi-solid metal forming by cooling slope method

Engineering Solid Mechanics ◽

10.5267/j.esm.2016.11.001 ◽

2017 ◽

pp. 9-14 ◽

Cited By ~ 3

Author(s):

Mohammad Mahdi Kaykha

Keyword(s):

Aluminum Alloy ◽

Metal Forming ◽

Cooling System ◽

Solid Metal ◽

Cooling Slope ◽

Slope Method ◽

Semi Solid

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Influence of Si and Mg Contents on the Mechanical Behavior of Al-Mg-Si Alloys in the Semi-Solid State under Isothermal and Non-Isothermal Conditions

Materials Science Forum ◽

10.4028/www.scientific.net/msf.690.73 ◽

2011 ◽

Vol 690 ◽

pp. 73-76

Author(s):

Eliane Giraud ◽

Michel Suéry ◽

Michel Coret

Keyword(s):

Solid State ◽

Aluminum Alloys ◽

Mechanical Behavior ◽

Solid Fraction ◽

Solid Alloy ◽

Isothermal Conditions ◽

Formation Of Cracks ◽

Semi Solid ◽

Si Content ◽

Mg Content

The shear behavior of aluminum alloys containing increased amounts of Si or Mg compared with the 6061 alloy has been investigated by carrying out isothermal and non-isothermal tests in the mushy state during solidification. In isothermal conditions, it is shown that (i) an increase in Mg content leads to a more resistant semi-solid alloy compared with the 6061 alloy for the same solid fraction and (ii) an increase in Si content leads to a more brittle mushy alloy. In non-isothermal conditions, stress increases continuously with decreasing temperature with the formation of cracks for some compositions. This study shows that an increase in Mg content seems to be the most appropriate solution to reduce the formation of cracks in a solidifying 6061 alloy.

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Modelling of Extrusion Process for Aluminium A356 Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.217-218.188 ◽

2014 ◽

Vol 217-218 ◽

pp. 188-194 ◽

Cited By ~ 1

Author(s):

Sudip Simlandi ◽

Nilkanta Barman ◽

Himadri Chattaopadhyay

Keyword(s):

Shear Stress ◽

Solid State ◽

Numerical Solutions ◽

Energy Requirement ◽

A356 Alloy ◽

Extrusion Process ◽

Solid Alloy ◽

Governing Equations ◽

Semisolid Alloy ◽

Semi Solid

In the present work, a model is developed to study extrusion process of A356 alloy in semi-solid state. The distinct rheology of the semisolid alloy reduces energy necessity during extrusion process. Accordingly, a proper rheological model of the alloy is considered in the model towards a detailed study of the process. A combination of analytical and numerical solutions is considered for solving the governing equations. The work finally predicts distribution of velocity and shear stress of the alloy under shear in the considered domain. It also predicts the energy requirement during the extrusion process. It is demonstrated that for semisolid extrusion, reasonably less energy is required as compared to a conventional extrusion process Keywords: Extrusion, semi-solid alloy, apparent viscosity, extrusion power

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Cooling Efficiencies of a NiTi-Based Cooling Process

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation ◽

10.1115/smasis2013-3249 ◽

2013 ◽

Cited By ~ 6

Author(s):

Marvin Schmidt ◽

Andreas Schütze ◽

Stefan Seelecke

Keyword(s):

Solid State ◽

Thermodynamic Analysis ◽

Cooling System ◽

Analysis Method ◽

Efficiency Ratio ◽

Cooling Process ◽

First Results ◽

Work Input ◽

Underlying Mechanisms ◽

The Impact

Energy saving and environmental protection are topics of growing interest. In the light of these aspects alternative refrigeration principles become increasingly important. Shape memory alloys (SMA), especially NiTi alloys, generate a large amount of latent heat during solid state phase transformations, which can lead to a significant cooling effect in the material. These materials do not only provide the potential for an energy-efficient cooling process, they also minimize the impact on the environment by reducing the need for conventional ozone-depleting refrigerants. Our paper, presenting first results obtained in a project within the DFG Priority Program SPP 1599 “Ferroic Cooling”, focuses on the thermodynamic analysis of a NiTi-based cooling system. We first introduce a suitable cooling process and subsequently illustrate the underlying mechanisms of the process in comparison with the conventional compression refrigeration system. We further introduce a graphical solution to calculate the energy efficiency ratio of the system. This thermodynamic analysis method shows the necessary work input and the heat absorption of the SMA in stress/strain- or temperature/entropy-diagrams, respectively. The results of the calculations underline the high potential of this solid-state cooling methodology.

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