Alloys for Semisolid Processing

Zoqui, Eugênio José

doi:10.1016/b978-0-08-096532-1.00520-3

Cited by 20 publications

(18 citation statements)

References 96 publications

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“…The amount, distribution, morphology, and size of the Al 15 (FeMnCr) 3 Si 2 particles ( Figure 11 and columns P s and f P in Table 6) in the B319+Fe alloy are similar for all of the soak times and temperatures analyzed, indicating that they are thermodynamically stable. Figure 12 shows these particles for two extreme heat treatment conditions (575 • C-0 s and 595 • C-90 s).…”

Section: Microstructural Evolution During Isothermal Heat Treatmentmentioning

confidence: 85%

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Thixoforming of an Fe-Rich Al-Si-Cu Alloy—Thermodynamic Characterization, Microstructural Evolution, and Rheological Behavior

Brollo

Proni

Zoqui

2018

Metals

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Thixoforming depends on three factors: (a) the thermodynamic stability of the solid-to-liquid transformation in the presence of temperature fluctuations; (b) the size and morphology of the solid particles in the liquid in the semisolid state; and (c) the rheology of the semisolid slurry during formation. In this study, these parameters were characterized for an Al-Si-Cu alloy with a high Fe content (B319+Fe alloy). Fe is usually found in raw metal produced by recycling, and its removal increases processing costs. This study is an attempt to use this lower-cost alloy for the thixoforming route. Thermodynamic analysis was performed by numerical simulation (under Scheil conditions) and the application of the differentiation method (DM) to differential scanning calorimetry (DSC) curves recorded during heating cycles up to 700 • C at 5, 10, 15, 20, and 25 • C/min. The processing window was evaluated by comparing the results of the DM and those of the analysis of open-die thixoforged samples after isothermal heat treatment at 575, 582, 591, and 595 • C for 0, 30, 60, and 90 s. The microstructural and rheological behavior of the semisolid slurry was analyzed at 591 and 595 • C for all four soak times. Isothermal heat treatment caused the refinement and spheroidization of the solid phase. Good agreement between the predicted thermodynamic behavior and the microstructural behavior of the thixoformed B319+Fe alloy samples was observed. Although the alloy exhibited a coarse microstructure, it was microstructurally and rheologically stable at all temperatures and for all the soak times studied, indicating that B319+Fe is a promising raw material for thixoforming.

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Section: Microstructural Evolution During Isothermal Heat Treatmentmentioning

confidence: 85%

“…SSM processing can be performed by cooling liquid metal to the semisolid state in a range of operations called rheocasting [3] or by heating solid metal to the semisolid condition in a range of operations called thixoforming [4].…”

Section: Introductionmentioning

confidence: 99%

Thixoforming of an Fe-Rich Al-Si-Cu Alloy—Thermodynamic Characterization, Microstructural Evolution, and Rheological Behavior

Brollo

Proni

Zoqui

2018

Metals

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“…The main objective of this work is to improve the thixoforming process of the 355 aluminum alloy as previous studies indicated excellent controllable thermodynamic 6,7 behavior, but difficulties concerning morphology that does not respond well to grain chemical refining. It is also reported that 355 alloy has excellent mechanical properties with a yield strength of 230 MPa, ultimate tensile strength of 320 MPa and an elongation of up to 7% after solubilization and aging heat treatment 5 .…”

Section: Introductionmentioning

confidence: 97%

“…Therefore, the understanding of phase transformation, microstructure stability, and viscous behavior of the slurry is fundamental for the development of these processes. Rheocasting and Thixoforming are the denominations of processes of forming metals alloys in the semisolid state, and the main requirements for these processes are a) thermodynamics -controllable solid liquid transition; b) refined and globularized morphology and c) behavior of viscous fluid 5 .…”

Section: Introductionmentioning

confidence: 99%

The use of ECAP in the Microstructural Conditioning of the 355 Aluminum Alloy for Thixoforming*

2020

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The purpose of this study is to analyze the use plastic deformation (ECAP-Equal Channel Angular Pressing) in the preparation of the 355 aluminum for posterior use in Thixoforming. For this purpose, the 355 alloy, in the as cast state and after a pass of ECAP was heated to temperatures of 575 and 595 °C, enough to produce 45 and 55% of liquid fraction, for times of 0, 30, 60 e 90s. In these conditions, it is possible to obtain a refined globular structure with the size of a grain, close to 75 µm, globule size of 55 µm and high sphericity (around 0.66), parameters which are excellent for this kind of processing. Hot compression tests at the same temperatures and holding times determine the rheological behavior. Maximum processing strain was obtained around 1 MPa for the sample in ECAped condition against 4 MPa of the as cast condition, which corresponds to maximum viscosity around 10 5 Pa.s, (molten glass, clay), inferior to the as cast condition (11.5 * 10 5 Pa.s). Therefore, the ECAPed 355 alloy is an easily conformable material very likely to be applied to semisolid processing.

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“…Semisolid processing (SSP) is commercially a relatively new metal-forming technology, although it was first introduced in the early 1970s, which competes directly with conventional casting and/or die-casting processes to produce near-net-shape components. SSP can be divided into two major routes: rheocasting, which involves forming the semisolid slurry of nondendritic microstructure directly from a controlled partially solidified melt in one single step, and thixoforming, which involves processing the melt in a separate stage, solidifying the melt completely, and then reheating the slugs back into the semisolid state, followed by the forming operation [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Cooling Behavior and Microstructure of Semisolid A201 Aluminum Alloy Prepared by the SEED Process

Gao

Zhu

et al. 2019

Metals

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The biggest challenge in semisolid processing of high-performance aluminum alloys is the narrow temperature processing windows of these alloys, and as a result, the preparation of qualified semisolid slurries is very important. High solid fraction slurries of high-strength A201 alloy were prepared by the Swirled Enthalpy Equilibration Device (SEED) process. The cooling behavior and microstructures of the A201 slurries produced by the standard, as well as a modified, SEED process were investigated. The results show that qualified A201 slurry can be produced by decreasing the pouring temperature and controlling the processing time in the SEED process. The modified SEED process significantly reduced the radial temperature gradient of the melt, due to the slow cooling rates involved, with the resulting slurries being more uniform, with more spherical microstructures, as compared to those produced by the standard SEED process. The formation of the nondendritic grain structure in the SEED process is attributed to the uniformly distributed large number of nuclei within the melt and the slow cooling of the melt in the containing crucible.

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Alloys for Semisolid Processing

Cited by 20 publications

References 96 publications

Thixoforming of an Fe-Rich Al-Si-Cu Alloy—Thermodynamic Characterization, Microstructural Evolution, and Rheological Behavior

Thixoforming of an Fe-Rich Al-Si-Cu Alloy—Thermodynamic Characterization, Microstructural Evolution, and Rheological Behavior

The use of ECAP in the Microstructural Conditioning of the 355 Aluminum Alloy for Thixoforming*

Cooling Behavior and Microstructure of Semisolid A201 Aluminum Alloy Prepared by the SEED Process

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