Modeling of shear induced coarsening effects in semi-solid alloys

The current study aimed at analyzing the response of semisolid A357 aluminum alloys to unconventional thermal treatment cycles of T4/T6/T7 conditions. The mechanical, electrical, and microstructural characterizations of such semisolid alloys were investigated. The microstructure evolutions of Fe-intermetallic phases and strengthening precipitates were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The mechanical failure of such semi solid A357 aluminum alloys, used for suspension automotive parts, is mostly related to cracking issues which start from the surface due to hardness problems and propagate due to severe load variations. For these reasons, the multiple thermal aging cycles, in this study, are applied to enhance the mechanical properties and to have compromised values compared to those obtained by standard thermal treatments. The results obtained in this work indicate that the heat treatment of this alloy can be optimized. The results showed that the optimum characteristics of A357 semisolid alloys were obtained by applying thermal under-aging cycle, interrupted thermal aging cycles and a T7/T6 two steps aging treatment condition. The electrical conductivity and electron microscopy were applied in this study to analyze the characteristics of hardening phases formed due to different aging cycles applied to the alloys investigated.

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

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.141-143.653 ◽

2008 ◽

Vol 141-143 ◽

pp. 653-658 ◽

Cited By ~ 2

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.

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Yield stress phenomena in semi-solid alloys

International Journal of Material Forming ◽

10.1007/s12289-010-0886-x ◽

2010 ◽

Vol 3 (S1) ◽

pp. 779-782 ◽

Cited By ~ 4

Author(s):

A. Moll ◽

M. Modigell

Keyword(s):

Yield Stress ◽

Semi Solid ◽

Solid Alloys

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Improvement of Mechanical Properties of Semi-Solid Alloys by ECAP Processing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.123-125.483 ◽

2010 ◽

Vol 123-125 ◽

pp. 483-486 ◽

Cited By ~ 3

Author(s):

Fumiya Nomura ◽

Takuya Matsuba ◽

Tatsuya Tanaka ◽

Yutaka Imaida

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Ecap Processing ◽

Angular Pressing ◽

Fine Grain ◽

Additional Improvement ◽

Semi Solid ◽

Back Pressure Ecap ◽

Solid Alloys ◽

Number Of Passes

Recently, semi-solid processing is paid to attention in the field of the light alloys. By this method, it is improved ductility and fatigue strength. Although, because of those mechanical properties of the elongation and toughness is not excellent, the range that can be the application to parts is limited. On the other hand, it is reported that grain refinements cause improvement of ductility and appearance of super plasticity. Then, Equal-Channel Angular Pressing (ECAP) method is reported to be effective to the sample making of a bulk and ultra fine grain in various alloys in recent years. In this study, it tried to improve ductility and durability due to making ultra fine grain in AC4CH alloys by the ECAP method, and the influence of ECAP processing on the mechanical property of AC4CH was investigated. As the result, the ductility of AC4CH has improved by ECAP processing. However, the tensile strength of AC4CH declined along with the increase in the number of passes. So, for the purpose of additional improvement of tensile strength, ECAP-Back Pressure (ECAP-BP) method that was reported to be more effective for grain refinements than ECAP method was applied to semi-solid AC4CH and compared with ECAP method. As the result, the tensile strength of AC4CH was maintained by use of ECAP-BP. Moreover, both ductility and toughness of that have been also improved.

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

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.116-117.565 ◽

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).

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