Study of Solidification Time and Solidus Velocity on Porosity Formation in High Strength Aluminum Alloy Castings

The purpose of the present study was to discuss the effects of local solidification time and solidus velocity on porosity formation in high strength aluminum alloy casting. With systematic change in the riser size, together with variation of thickness and length, A201 aluminum alloys were cast in 100% silica sand molds. The porosity content of A201 aluminum alloy was affected by the local solidification time and solidus velocity in this study. The correlation between porosity content and solidification time is found to be split into 2 bands, each being associated with one of the two thicknesses of plate castings. The longer the solidification time, the more the porosity content was measured in the A201 aluminum alloy plate casting. And the faster the solidus velocity, the more the porosity content in this study. The porosity content of A201 aluminum alloy was influenced by both of solidification time and solidus velocity at same time in this study. Basically, shorter local solidification time with slow solidus velocity seems get lower porosity content in A201 aluminum alloy castings.

Relationship between cooling rate and microsegregation in bottom-chilled directionally solidified ductile irons

This study explores the relationship between cooling rate and microsegregation of directionally solidified ductile iron. The unidirectional heat transfer system used in this research is made up of a copper mold kept chilled by circulating water and embedded in the bottom of Furan sand mold. Thermocouples are connected to the computer measuring system to record the cooling curves of the castings at a distance of 0, 30, 60 and 90 mm from the chilled copper mold surface. Alloys including Mn, Cr, Cu, Ni and Ti were added to the specimens. Electron microprobe analysis (EPMA) was employed to examine distribution of elements between the dendrite arms and nodular graphite. Results show that unidirectional heat transfer affects directly the solidification mode and microstructure of the casting. The cooling curves reveal that local solidification time increases with increasing distance from the chilled copper mold surface. Different solidification rates with corresponding microstructure and element segregation were observed in the same unidirectionally solidified casting. Local solidification time was closely related to element segregation. The effective segregation coefficient (Keff) calculated using the Scheil equation was found to vary, according to the stage of solidification. The actual segregation characteristics of complex alloys generally follow the Scheil equation.

Effects of Thermal Gradient and Solidification Time on Porosity Content of A201 Aluminum Alloy Castings

The purpose of the present study was to discuss the effects of local solidification time and thermal gradient on porosity content in long solidification range A201 aluminum alloy plate castings. With systematic change in the riser size, together with variation of thickness and length, were cast in different kinds of molds. The sand molds with end chill for the plate castings were made of 100% silica sand. The porosity content of A201 aluminum alloy was affected by the local solidification time and thermal gradient at same time in this study. The correlation between porosity content and any individual thermal parameter is found to be split into 2 bands, each being associated with one of the two thicknesses of plate castings. The higher the thermal gradient, the lower the porosity content was measured in the A201 aluminum alloy plate casting. And high thermal gradient with short solidification time will get lower porosity content in aluminum alloy castings

Effects of Solidification Time on Porosity Content in A201 Aluminum Alloy Castings

The purpose of the present study was to discuss the effects of local solidification time on porosity content of long solidification range A201 aluminum alloy plate castings. With systematic change in the riser size, together with variation of thickness and length, were cast in different kinds of molds. The sand molds with end chill for the plate castings were made of 100% silica sand. The porosity content of A201 aluminum alloy was affected by the local solidification time in this study. The correlation between porosity content and solidification time is found to be split into 2 bands, each being associated with one of the two thickness of plate castings.

Numerical Optimization of the Casting of Ceramic Material EUCOR

Corundo-baddeleyit material (CBM) – EUCOR – is a heat- and wear-resistant material even at extreme temperatures. This article introduces a numerical model of solidification and cooling of this material in a non-metallic mold. The model is capable of determining the total solidification time of the casting and also the place of the casting which solidifies last. Furthermore, it is possible to calculate the temperature gradient at any point and time, and also determine the local solidification time and the solidification interval of any point. The local solidification time is one of the input parameters for the cooperating model of chemical heterogeneity. This second model and its application on EUCOR samples prove that the applied method of measuring the chemical heterogeneity provides the detailed quantitative information on the material structure and makes it possible to analyze the solidification process. The analysis of this process entails statistical processing of the measurement results of the heterogeneity of the EUCOR components and performs the correlation of individual components during solidification. The verification of both numerical models was conducted on a real cast 350 × 200 × 400 mm block.

Effects of Solidification Parameters on SDAS of A357 Alloy

In this investigation, experiments were carried out to study the relationship of solidification parameters and the secondary dendrite arm spacing (SDAS) in A357 alloy casting with various thicknesses under the same solidification condition. The results show that the cooling rate decreases as the thickness of specimens increases, the local solidification time increased, and SDAS increased. The relationships between the SDAS and cooling rate and local solidification time under the condition of furan resin self-hardening sand casting were obtained: SDAS = 20.8 tf 0.3, SDAS = 69.34 v -0.3. The mechanical properties have some linear relations with SDAS of A357 alloy after aging heat treatment. The correlations can be expressed: UTS=410.4-0.8SDAS and El%=7.9-0.05SDAS.

The Character of the Solidification Structure of Massive Ductile Cast-Iron Castings and its Prediction

An original three-dimensional (3D) model of solidification is used to describe the process of solidification and cooling of massive 500x1000x500 mm cast-iron castings in sand moulds. The calculated model of the kinetics of the temperature field of the casting is verified during casting with temperature measurements in selected points. The following dependences are later determined according to the experimental and calculated data: the average size of the graphite spheroids rg, graphite cells Rb and the average distances among the particles of graphite Lg – always as a function of the local solidification time θ [xi, yi, zi]. Furthermore, it has been found that the given basic characteristics of the structure of the cast-iron (rg, Rb and Lg) are a linear function of the logarithm of the local solidification time θ. The original spatial model of solidification can therefore be used in its first approximation for the assessment of the pouring structure of massive cast-iron castings.

Two Numerical Models for Optimization of the Foundry Technology of the Ceramics EUCOR

Corundo-baddeleyit material — EUCOR — is a heat- and wear-resistant material even at extreme temperatures. This article introduces a numerical model of solidification and cooling of this material in a non-metallic mould. The model is capable of determining the total solidification time of the casting and also the place of the casting which solidifies last. Furthermore, it is possible to calculate the temperature gradient in any point and time, and also determine the local solidification time and the solidification interval of any point. The local solidification time is one of the input parameters for the cooperating model of chemical heterogeneity. This second model and its application on samples of EUCOR prove that the applied method of measurement of chemical heterogeneity provides detailed quantitative information on the material structure and makes it possible to analyse the solidification process. The analysis of this process entails statistical processing of the results of the measurements of the heterogeneity of the components of EUCOR and performs correlation of individual components during solidification. The crystallisation process seems to be very complicated, where the macro- and microscopic segregations differ significantly. The verification of both numerical models was conducted on a real cast 350 × 200 × 400 mm block.