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The extraordinary effect of very low content of hybrid carbonaceous reinforcement on the microstructural and mechanical properties of 7075 aluminum alloy

Ezatpour H. R., Torabi Parizi M., Ebrahimi G. R.

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

263--286

EN

Until recently, the strengthening efficiency of carbonaceous reinforcements in aluminum-based matrix nanocomposites (AlMNCs) was lower than expected. The intrinsic characteristics of matrix and carbonaceous reinforcements and fabrication technique, which affected the microstructural characterization, played main roles in determining the performance of Cs/AlMNCs. In this study a novel strategy was developed via flake powder metallurgy followed by slurry blending combined with rheocasting and hot-extrusion processing to prepare hybrid AA7075-matrix composite reinforced with CNTs + GNPs. No Al4C3 phase was detected in Raman spectrums, while uniform dispersion of carbonaceous hybrid reinforcements with minimal structural damage was observed. There were ~ 9% and 39% decrease in the average grain size of the as-casted and extruded CNTs + GNPs/AA7075 composites, respectively, compared to AA7075 alloy. In the extruded CNTs + GNPs/AA7075 composite, plate precipitates were predominant and some lath-like dynamic precipitates were observed at the GNPs/AA7075 interfaces. The micro-hardness, tensile yield strength (TYS), ultimate tensile strength (UTS) and uniform elongation (UE) of the CNTs + GNPs/AA7075 composite were improved by ~ 17%, 51%, 7% and 20% compared to AA7075 alloy. An ultra-high yield strengthening efficiency of carbonaceous hybrid reinforcements in AA7075 alloy up to 3950 was obtained, where load bearing was the main strengthening mechanism and carbonaceous reinforcements illustrated bridging and pulling-out in the fracture surfaces of composite.

2

Grain Refinement of AlSi7Mg0,3 Alloy Cast by Rheocasting SEED

Bryksí Stunová B., Bryksí V., Vitkova J.

Archives of Foundry Engineering

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2018

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Vol. 18, iss. 3

161--166

EN

The paper concerns experimental work studying chemical composition, structures and selected mechanical properties of castings produced by rheocasting method SEED. After previous experiments, which showed inclusions in the primary phase α(Al) when observing structures, hypothesis of external nuclei was taken. The main goal of the work was to determine the influence of inoculation by various additions of titanium/boron based inoculant on the structure and properties of AlSi7Mg0,3 alloy. The master alloy AlTi5B1 was added in amounts of 0,05, 0,1, 0,15, 0,2 wt %. Metallographic observation by light and SEM microscopy was used for analysing the structures. Measurements of grain size were realised and evaluated. Brinell hardness measurements were performed. Chemical composition was measured by GDS analysis. Undertaken experiments did not prove the effect of inoculation of combined AlTi5B1 master alloy on castings made of AlSi7Mg0,3 alloy made by rheocasting SEED at given amounts and conditions.

3

Analysis of Defects in Castings Cast by Rheocasting Method SEED

Bryksi Stunova B., Bryksi V.

Archives of Foundry Engineering

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2016

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Vol. 16, iss. 3

15--18

EN

The paper analyses specific defects of castings produced by semi-solid casting process, especially rheocasting method SEED, which uses mechanical swirling for reaching proper structure in semisolid state with high content of solid fraction. Heat treated alloy AlSi7Mg0.3 was applied for producing an Engine Bracket casting part. For observing structure, metallographic observation by light and SEM microscopy was used. To analyse the process, software ProCAST was used to simulate the movements in shot chamber and filling of the mold.

4

Development, fashion, quality and innovations from SSM to rheocasting processes

Rosso M.

Archives of Materials Science and Engineering

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2015

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Vol. 71, nr 1

16--26

EN

Of this paper is to give an overview concerning some alternative methods for the production of enhanced performance light alloys components for critical industrial applications and to present an analysis of a new rheocasting process suitable fpr the manufacturing of high performance industrial components. Design/methodology/approach: Innovative design of some automotive parts, their characterization throught radiographic analysis to verify the integrity of the samples from metallurgical point of view. OM and SEM microstructural characterization, optical microscope, mechanical characterization based on samples machined from the produced parts. Findings: Semi-solid metal (SSM) processes demonstrated their capability to reduce the existing gap between casting and forging and during such a processes there are the opportunity to better control the defect level. Research limitations/implications: The produced parts possess excellent properties, some criticises are related to the use of ceramic cores. There is the need of innovation in industrial design to open the mentalities to new advantageous solutions. Practical implications: The principal goal to improve the competitiveness and energy savings associated to the production in high performance cars was fully accomplished. Originality/value: A study on the feasibility was included opening the route for prototype production characterized by an adequate strength as well as by higher esthetical appearance than the element produced by gravity casting process. The presence of the defects does not negatively influence or compromise the employment of the callipers neither in extreme condition, favouring their use on a very high performance cars. In the future, extension of the proposed process for the production of other important applications are expected.

5

Thixocasting and rheocasting technologies, improvements going on

Rosso M.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 54, nr 1

110--119

EN

Purpose: The paper proposes an overview of the actual most important and applied rheocasting technologies for the manufacturing of high performance Al components. Some excellent results recently attained in industrial applications are presented and discussed. Design/methodology/approach: Samples were machined from the produced parts and mechanical tests, i.e. tensile and impact, were executed on series of samples; moreover, microstructure features and the morphology of fractures were observed to check the quality of alloys and of produced castings. Findings: Despite the numerous rheocasting processes recently developed, it appears that their industrial application is still limited and some only are really interesting for the production of high performance component. The done investigations show that the use of a very simple and well controlled process leads to produce parts having excellent properties and reliability. The results obtained up to now suggest that the rheocasting route can be considered an attractive fabrication technology to produce high quality products, especially for aluminium alloys. Research limitations/implications: A lot of rheocasting processes are proposed, but for the final success it is necessary to choice a really valid process and to maintain all the steps under a strict control. Practical implications: The obtained results can be used for searching the appropriate way of improving the performance of highly stressed parts, using a very competitive and simple rheocasting process, contributing to make aluminium and its alloys still more attractive for light-weighting components for structural, as well as for automotive and aeronautic/aerospace applications. Originality/value: The main SSM technologies and future trends are presented and discussed. The properties of A356 and A357 aluminium alloys were investigated to establish the influence of the adopted Rheocasting process on the final performances and reliability of the produced parts.