Prediction of shrinkage allowance for tool design of aluminium alloy (A356) investment casting

Nayak, Ramesh Kumar; Venugopal, S.

doi:10.1016/j.matpr.2018.10.300

Cited by 9 publications

(3 citation statements)

References 9 publications

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“…Deviations between the PLA pattern and the final A356 lattice structure (Step II) can be attributed to dimensional changes that occur during two distinct processing stages; (i) forming the investment cast: due to the expansion of the investment gypsum mold during its curing which involves the loss of water and the transformation of gypsum from α (cristobalite) to β (quartz) 75 ; and (ii) during/after A356 melt casting: due the contraction of the A356 alloy during the solidification and subsequent cooling 76 , 77 . The net result is that the final A356 cast samples tend to display slightly larger dimensions than the PLA samples.…”

Section: Resultsmentioning

confidence: 99%

Macro-, meso- and microstructural characterization of metallic lattice structures manufactured by additive manufacturing assisted investment casting

Carneiro

Rawson

Puga

et al. 2021

Sci Rep

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Cellular materials are recognized for their high specific mechanical properties, making them desirable in ultra-lightweight applications. Periodic lattices have tunable properties and may be manufactured by metallic additive manufacturing (AM) techniques. However, AM can lead to issues with un-melted powder, macro/micro porosity, dimensional control and heterogeneous microstructures. This study overcomes these problems through a novel technique, combining additive manufacturing and investment casting to produce detailed investment cast lattice structures. Fused filament fabrication is used to fabricate a pattern used as the mold for the investment casting of aluminium A356 alloy into high-conformity thin-ribbed (~ 0.6 mm thickness) scaffolds. X-ray micro-computed tomography (CT) is used to characterize macro- and meso-scale defects. Optical and scanning electron (SEM) microscopies are used to characterize the microstructure of the cast structures. Slight dimensional (macroscale) variations originate from the 3D printing of the pattern. At the mesoscale, the casting process introduces very fine (~ 3 µm) porosity, along with small numbers of (~ 25 µm) gas entrapment defects in the horizontal struts. At a microstructural level, both the (~ 70 μm) globular/dendritic grains and secondary phases show no significant variations across the lattices. This method is a promising alternative means for producing highly detailed non-stochastic metallic cellular lattices and offers scope for further improvement through refinement of filament fabrication.

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Section: Resultsmentioning

confidence: 99%

Macro-, meso- and microstructural characterization of metallic lattice structures manufactured by additive manufacturing assisted investment casting

Carneiro

Rawson

Puga

et al. 2021

Sci Rep

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“…It is suggested that in near complete casting It is known that during its thermal cycle, the plaster releases its water content losing mass, however, the overall mold can suffer an expansion due to the αto βtransitions in the cristobalite (5.7% in volume) and quartz (4.3% in volume) components of the plaster [64]. Additionally, aluminum alloys suffer from considerable shrinkage and linear contraction during solidification [65,66]. These effects are able to influence the final cast sample dimensions, in which the higher dimensions of rib length show a similar increase in both horizontal and vertical configurations (2.5% expansion-according to Figure 7).…”

Section: Discussionmentioning

confidence: 99%

Thin-Rib and High Aspect Ratio Non-Stochastic Scaffolds by Vacuum Assisted Investment Casting

Carneiro¹,

Puga

Peixinho³

et al. 2019

JMMP

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Cellular structures are a classic route to obtain high values of specific mechanical properties. This characteristic is advantageous in many fields, from diverse areas such as packaging, transportation industry, and/or medical implants. Recent studies have employed additive manufacturing and casting techniques to obtain non-stochastic cellular materials, thus, generating an in situ control on the overall mechanical properties. Both techniques display issues, such as lack of control at a microstructural level in the additive manufacturing of metallic alloys and the difficulty in casting thin-rib cellular materials (e.g., metallic scaffolds). To mitigate these problems, this study shows a combination of additive manufacturing and investment casting, in which vacuum is used to assist the filling of thin-rib and high aspect-ratio scaffolds. The process uses 3D printing to produce the investment model. Even though, vacuum is fundamental to allow a complete filling of the models, the temperatures of both mold and casting are important to the success of this route. Minimum temperatures of 250 °C for the mold and 700 °C for the casting must be used to guarantee a successful casting. Cast samples shown small deviations relatively to the initial CAD model, mainly small expansions in rib length and contraction in rib thickness may be observed. However, these changes may be advantageous to obtain higher values of aspect ratio in the final samples.

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“…В настоящее время такие специальные способы литья, как литье в кокиль [1,2], литье по выплавляемым [3,4] и газифицируемым [5,6] моделям, имеют широкое распространение в мировой практике получения отливок с высокой размерной точностью. Однако, несмотря на развитие теоретических и технологических основ для указанных способов литья, остается ряд проблем, связанных с отдельными технологическими этапами.…”

Section: Introductionunclassified

Investigation of linear shrinkage of model compounds and interaction mechanisms in the «lost wax pattern – refractory ceramic mold» system

Никитин

D’yachkov

Никитин

et al. 2019

Izv.VUZ. Tsvet. Met.

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Выполнено исследование свободной линейной усадки ненаполненных (ПС50-50, МВС3-Т, Romocast 105, Romocast 152) и наполненных (Romocast 252, Romocast 325) модельных составов в зависимости от температуры окружающей среды. Полученные результаты выявили следующие основные особенности в изменении указанного технологического параметра. Установлено, что наибольшей свободной линейной усадкой обладают ненаполненные модельные составы, а наименьшей -наполненные. При этом процессы, связанные со свободной линейной усадкой, протекали в образцах в течение длительного времени (до 24 ч). Это, вероятно, связано с продолжительностью процессов полимеризации и низкой теплопроводностью модельных составов. Изменение температуры окружающей среды в интервале от -5 до +35 °С оказывает существенное влияние на величину изменения линейных размеров образцов из исследованных модельных составов. Изменение длины образцов из ненаполненных модельных составов варьируется в диапазоне от +0,3 до -0,4 %, а из наполненных -от +0,2 до -0,15 %. При охлаждении до -5 °С и последующем нагреве до +20 °С образцов из ненаполненных составов их исходная длина уменьшается в среднем на 0,2 мм, а при нагреве до +35 °С и последующем охлаждении до +20 °С она увеличивается в среднем на 0,2-0,3 мм. При аналогичных изменениях температуры окружающей среды у образцов из наполненных модельных составов изменение размеров составляет не более 0,1 мм. Для устранения растрескивания огнеупорных керамических форм предложено проводить захолаживание системы «выплавляемая модельогнеупорная керамическая форма», что обеспечивает гарантированный зазор между моделью и формой и нивелирует негативное влияние расширяющегося модельного состава.Ключевые слова: литье по выплавляемым моделям, свободная линейная усадка, огнеупорная керамическая форма, система «выплавляемая модель -огнеупорная керамическая форма».Никитин К.В. -докт. техн. наук, доцент, декан факультета машиностроения, металлургии и транспорта Самарского государственного технического университета (СамГТУ) (443100, г. Самара, ул. Молодогвардейская, 244).

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Prediction of shrinkage allowance for tool design of aluminium alloy (A356) investment casting

Cited by 9 publications

References 9 publications

Macro-, meso- and microstructural characterization of metallic lattice structures manufactured by additive manufacturing assisted investment casting

Macro-, meso- and microstructural characterization of metallic lattice structures manufactured by additive manufacturing assisted investment casting

Thin-Rib and High Aspect Ratio Non-Stochastic Scaffolds by Vacuum Assisted Investment Casting

Investigation of linear shrinkage of model compounds and interaction mechanisms in the «lost wax pattern – refractory ceramic mold» system

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