Materials Processing during Casting

Fredriksson, Hasse; Åkerlind, Ulla

doi:10.1002/9780470017920

Cited by 112 publications

(107 citation statements)

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“…Pure solidification from the wall should result in compressive stresses. 24 This supports that the residual stress formation is dominated by the part lateral contraction and part distortion around the fixed side during cooling, opposing the finding of Hofer et al 11 …”

Section: Parameters (B) and (D) Is Shown Inmentioning

confidence: 84%

Effect of Process Parameters on Distortion and Residual Stress of High-Pressure Die-Cast AZ91D Components

2017

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This paper presents a study of distortion and residual stress within a high-pressure die-cast AZ91D component, cast under different processing conditions. The influence of process parameters, i.e., die temperature, cooling time, intensification pressure and first-phase injection speeds, was examined. Distortions were measured using the inhouse standard analog quality control fixture. Residual stress depth profiles were measured using a prism holedrilling method. It was found that the most important process parameter affecting the distortion was intensification pressure and the second most important was temperature difference between the two die halves (fixed and moving side). Tensile residual stresses were found very near the surface. Increasing the intensification pressure resulted in an increased level of tensile residual stresses.

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Section: Parameters (B) and (D) Is Shown Inmentioning

confidence: 84%

Effect of Process Parameters on Distortion and Residual Stress of High-Pressure Die-Cast AZ91D Components

2017

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“…not fully sufficient to describe the mould material's influence on cooling conditions but it gives a good approximation of how cooling conditions change when mould materials are changed [2].…”

Section: / 23mentioning

confidence: 99%

“…The undercooling is determined by the balance between heat extraction through the solidified layer to the mould and latent heat released as the eutectic cells grow. It is well known that the growth velocity of the eutectic cells is also a function of the undercooling [2]. It is therefore most likely that the transition from dense to free growth is governed by a complex interaction between the spatial thermal gradient, cooling rate and nucleation kinetics.…”

Section: Zone 2 -The Transition Layermentioning

confidence: 99%

“…The formation of casting porosity is known to be significantly influenced by the growth morphology of the solidifying alloy, and in particular the feeding of liquid through the semi-solid mush [2]. It is therefore important to understand the operative growth morphologies in order to understand pore formation.…”

Section: Introductionmentioning

confidence: 99%

“…Even in a binary alloy this complicates feeding as the growth modes of both the α-Al phase and the eutectic need to be taken into account. Complicating matters further is the common practice of adding Na or Sr modifiers during the production of hypoeutectic and eutectic Al-Si alloy castings to alter the morphology of the eutectic silicon so that it becomes fibrous rather than acicular, thus improving the alloy's mechanical properties, particularly its ductility [2].…”

Section: Introductionmentioning

confidence: 99%

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A new multi-zone model for porosity distribution in Al–Si alloy castings

2013

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Link back to DTU Orbit Citation (APA):Tiedje, N. S., Taylor, J. A., & Easton, M. A. (2013). A new multi-zone model for porosity distribution in Al-Si alloy castings. Acta Materialia, 61(8), 3037-3049. DOI: 10.1016/j.actamat.2013 AbstractA new multi-zone model is proposed that explains how porosity forms in various regions of a casting under different conditions and leads to distinct zonal differences in pore shape, size and distribution. This model was developed by considering the effect of cooling rate on solidification and distribution of porosity in Al-Si alloys cast as plates in moulds made with silica, ilmenite or zirconia sand cores or steel chills facing the major plate faces. The alloys cast were Al-7wt% Si and Al-12.5wt% Si in unmodified and modified forms, the latter with either Na or Sr addition. It is found that regardless of cooling condition, Si content and modification treatment the microstructure can be divided into three zones of varying size (across the casting thickness) that are determined by the local cooling conditions and the nucleation and growth mode of the Al-Si eutectic. The zones are: (1) an outer shell-like zone where directional columnar dendritic grains and a fine celled, coherent eutectic form a low porosity shell at the casting surface; (2) a transitional zone where equiaxed, eutectic cells grow between columnar dendritic grains and irregular pores become trapped in the mush; and finally, (3) a central zone where the thermal gradient is low and equiaxed dendritic grains and eutectic cells grow at the centre of the casting and larger rounded pores tend to form. The paper discusses how Si content, modification type and cooling conditions influence the location and size (i.e. depth) of each of these zones and how the distribution of porosity is thus affected.

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