Thixoforming of Aluminium-Silicon Alloys in a Mechanical Eccentric Press

Zoqui, Eugênio José; Lourençato, Luciano Augusto; Benati, Davi Munhoz

doi:10.4028/3-908451-59-0.517

Cited by 2 publications

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“…Nevertheless, the values for these parameters are still within the typical range of values for Fe-2.6 wt%C-1.5 wt%Si cast iron. A similar phenomenon occurs for A356 and A357 aluminum alloys, which exhibit mechanical properties inferior to or close to those of die cast parts (Zoqui et al, 2008;NADCA, 2006). As with aluminum alloys, further heat treatment may improve the mechanical properties of the thixoformed Fe-2.6 wt%C-1.5 wt%Si cast iron used here by increasing the YS, UTS and E.…”

Section: Characterization Of Mechanical Propertiesmentioning

confidence: 73%

“…The methodology used here to assess the thixoformability of an alloy is the same as that described earlier by Zoqui et al (2008), Zoqui and Torres (2010) and Zoqui and Naldi (2011). The methodology adopted in the Foundry and Thixoforming Laboratory (FTL) at the Faculty of Mechanical Engineering, Unicamp, to evaluate the thixoformability of a specific alloy is based on six basic steps: (a) thermodynamic analysis of the solid-to-liquid transition; (b) manufacture of the alloy and characterization of its initial microstructure; (c) evaluation of microstructural stability in the semisolid state; (d) determination of the combined effect of the liquid fraction and the morphology of the remaining solid on the alloy's rheological behavior; (e) investigation of the thixoforming procedure itself; and (f) determination of the final microstructure and final mechanical characteristics.…”

Section: Methodsmentioning

confidence: 99%

“…Eccentric presses have the advantage that they are simple and easy to operate; however, final solidification after forming occurs without a load, which is a disadvantage, as solidification under continuous load prevents porosity, avoids shrinkage phenomena and results in better mechanical properties (Zoqui et al, 2008).…”

Section: Thixoforming Proceduresmentioning

confidence: 99%

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Mechanical properties of thixoformed hypoeutectic gray cast iron

Roca

Fals

Zoqui

2015

Journal of Materials Processing Technology

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a b s t r a c tThe effects of thixoforming process variables on the final mechanical properties of a specially designed hypoeutectic cast iron were studied. An Fe-2.6 wt%C-1.5 wt%Si alloy was prepared using conventional sand casting molds and thixoformed in an eccentric press. Different temperatures and heat-treatment holding times were tested. After being heated to the semisolid state at 1160 • C and 1180 • C and held at these temperatures for 0, 30, 60 and 90 s, the samples were subjected to the thixoforming process. The holding time in the semisolid range simulates the industrial heating process, which is time controlled rather than temperature controlled. The results indicate that the forces applied during thixoforming are closely related to the liquid fraction of the hypoeutectic gray cast iron. A comparative analysis of the behavior of the tensile properties, Vickers microhardness and porosity before and after thixoforming was carried out. The stress-strain curves were similar for the different liquid fractions studied: at 1160 • C the average values were YE = 282 MPa, UTS = 289 MPa, E = 0.21% and Vickers microhardness = 274HV, while at 1180 • C the corresponding figures were YE = 272 MPa, UTS = 277 MPa, E = 0.2% and Vickers microhardness = 257HV. The small variations in tensile properties can be attributed to the final graphite morphology of the thixoformed alloy. The results also show that after thixoforming, the porosity of the Fe-2.6 wt%C-1.5 wt%Si alloy decreased for all experimental conditions and had a maximum value of 5%. There was no significant difference in hardness between the thixoformed material and the as-cast alloy.

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Section: Characterization Of Mechanical Propertiesmentioning

confidence: 73%

Section: Methodsmentioning

confidence: 99%

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Mechanical properties of thixoformed hypoeutectic gray cast iron

Roca

Fals

Zoqui

2015

Journal of Materials Processing Technology

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Evolution of Microstructure in Semi-Solid of Al-2wt%Si-0.5wt%Mg and Al-4wt%Si-05wt% Alloys during Isothermal Holding

Lourençato

Zoqui

2014

AMR

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Thixoforming technology has made considerable advances since its initial discovery in 1973. Although, after almost 40 years, few raw materials are still used as thixoforming materials. The Al-Si-Mg alloys often used for semi-solid state processing are notably casting alloys like A356 and A357. The development of new alloys specially tailored for thixoforming is a new challenge in this area of research. This paper will present some results related to the study of Al-2wt%Si-05wt%Mg and Al-4wt%Si-05wt%Mg alloy obtained via conventional foundry followed by ultra-refining. The results are compared with a commercial Al-7wt%Si-05wt%Mg alloy. Also presents its morphological evolution in the re-heating of the material to obtain the solid fraction of 45% and 60% in four different holding times 0, 30, 90 e 210 seconds. After re-heating, with the determination of grain size and globules, held the study Rheocast Quality Index (RQI) and Shape Factor (SF), parameter that helps to quantify the efficiency of the treatment globularization to obtain semi-solid structure with globular structure. The morphological evolution showed that the increase of holding time resulted in a minor increase in the globule size of the structure. The RQI values show that there is little morphological evolution in the treatment of globularization for alloys with percentage of Si, indicating alloys with percentage below of 4wt% Si is the most appropriate for thixoforming.

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Thixoforming of Aluminium-Silicon Alloys in a Mechanical Eccentric Press

Cited by 2 publications

References 0 publications

Mechanical properties of thixoformed hypoeutectic gray cast iron

Mechanical properties of thixoformed hypoeutectic gray cast iron

Evolution of Microstructure in Semi-Solid of Al-2wt%Si-0.5wt%Mg and Al-4wt%Si-05wt% Alloys during Isothermal Holding

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