scholarly journals Nodule Count, End of Solidification Cooling Rate, and Shrinkage Porosity Correlations in High Silicon Spheroidal Graphite Iron

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 155
Author(s):  
Gorka Alonso ◽  
Doru Michael Stefanescu ◽  
Beñat Bravo ◽  
Gorka Zarrabeitia ◽  
Ramon Suarez
Keyword(s):  
Cooling Rate ◽  
Solidification Process ◽  
Sem Analysis ◽  
Shrinkage Porosity ◽  
Laboratory Research ◽  
Spheroidal Graphite ◽  
Nodule Count ◽  
Nucleation Sites ◽  
Lower Porosity ◽  
High Silicon

High-silicon spheroidal graphite (SG) irons present higher changes of density during the solidification process when compared to normal SG irons. This special behavior is particularly significant in the last stages of solidification, where the graphite expansion may become insufficient to compensate the contraction of the austenite and the risk of microporosity formation increases. The goal of this laboratory research was to establish correlations between the different levels of nodule count obtained using five commercial inoculants, the cooling rate at the end of solidification, and the shrinkage porosity propensity. The analysis was conducted on thermal analysis cups that were sectioned and evaluated for microstructure by optical metallography and by 2D analysis with the Image J software to quantify the size of the microporosity region. It was found that a higher nodule count, associated with higher cooling rate at the end of solidification, generates lower porosity. SEM analysis was conducted to study the nature of nuclei. Complex (MgSiAl)N nitrides were found as the main nucleation sites for graphite.

scholarly journals Mechanical Properties of Al-Si-Mg Alloy Castings as a Function of Structure Refinement and Porosity Fraction

2012 ◽  
Vol 12 (4) ◽  
pp. 57-64
Author(s):  
M. Hajkowski ◽  
Ł. Bernat ◽  
J. Hajkowski
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Quartz Sand ◽  
Thick Plate ◽  
Structure Refinement ◽  
Solidification Process ◽  
Shrinkage Porosity ◽  
Alloy Castings ◽  
Prediction Of Mechanical Properties ◽  
Porosity Fraction

Abstract During design of the casting products technology, an important issue is a possibility of prediction of mechanical properties resulting from the course of the casting solidification process. Frequently there is a need for relations describing mechanical properties of silumin alloys as a function of phase refinement in a structure and a porosity fraction, and relations describing phase refinement in the structure and the porosity fraction as a function of solidification conditions. The study was conducted on castings of a 22 mm thick plate, made of EN AC-AlSi7Mg0,3 alloy in moulds: of quartz sand, of quartz sand with chill and in permanent moulds. On the basis of cooling curves, values of cooling rate in various casting parts were calculated. The paper also presents results of examination of distance between arms in dendrites of a solid solution α (DASL), precipitations length of silicon in an eutectic (DlSi) and gas-shrinkage porosity (Por) as a function of cooling rate. Statistical relations of DASL, DlSi, Por as a function of cooling rate and statistical multiparameter dependencies describing mechanical properties (tensile strength, yield strength, elongation) of alloy as a function of DASL, DlSi and Por are also presented in the paper.

Effect of Nodule Count and Cooling Rate on As-Cast Matrix of a Cu-Mo Spheroidal Graphite

1999 ◽  
Vol 8 (3) ◽  
pp. 325-329 ◽  
Author(s):  
R. Salazar F. ◽  
M. Herrera-Trejo ◽  
M. Castro ◽  
J. Méndez N. ◽  
J. Torres T. ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Spheroidal Graphite ◽  
Nodule Count

scholarly journals Kaolinite Claystone-Based Geopolymer Materials: Effect of Chemical Composition and Curing Conditions

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 444 ◽  
Author(s):  
Pavlína Hájková
Keyword(s):  
Chemical Composition ◽  
Water Glass ◽  
Chemical Elements ◽  
Solidification Process ◽  
Ease Of Use ◽  
Raw Material ◽  
Curing Conditions ◽  
Low Viscosity ◽  
Lower Porosity ◽  
Curing Methods

This work describes the role of chemical composition and curing conditions in geopolymer strength, leachability of chemical elements and porosity. The study focuses on geopolymer material prepared from calcined kaolinite claystone, which is not studied frequently as a raw material for geopolymer production, although it has a high application potential as it is easily commercially available and allows preparation of geopolymers with low viscosity. The composition of geopolymers and their curing methods were selected considering their ease of use in the praxis. Therefore, the potassium water glass itself was used as alkali activator without any KOH or NaOH addition. Chemical composition was changed only by the density of water glass in the range of 1.2 to 1.6 g·cm−3. Geopolymers were cured at a temperature within the range of 5 °C–70 °C to speed up the solidification process as well as by microwave radiation. High compressive strengths were obtained for geopolymers with the highest densities of the water glass (1.5 and 1.6 g·cm−3) in dependence on various curing conditions. Higher strengths were achieved in the case of samples where the solidification was not accelerated. The samples cured at lower temperatures (5 °C) showed lower porosity compared to the other curing types. The lowest leachability of Si and alkalis was reached for the samples with water glass density 1.5 g·cm−3.

scholarly journals Study of the Effect of Carbon on the Contraction of Hypo-Peritectic Steels during Initial Solidification by Surface Roughness

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 982 ◽  
Author(s):  
Dazhi Pu ◽  
Guanghua Wen ◽  
Dachao Fu ◽  
Ping Tang ◽  
Junli Guo
Keyword(s):  
Surface Roughness ◽  
Cooling Rate ◽  
Solidification Process ◽  
Casting Process ◽  
Continuous Casting Process ◽  
Peritectic Steel ◽  
Laser Confocal Microscope ◽  
Initial Solidification

In the continuous casting process, the shrinkage of the peritectic phase transition during the initial solidification process has an important influence on the surface quality of peritectic steel. The initial solidification process of 0.10C%, 0.14C%, and 0.16C% peritectic steels was observed in situ by a high temperature laser confocal microscope, and the contraction degree during initial solidification was characterized by surface roughness. The results showed that under the cooling rate of 20 °C/s, the surface roughness value Ra(δ/γ) of 0.10C% peritectic steel was 32 μm, the Ra(δ/γ) value of 0.14C% peritectic steel was 25 μm, and the Ra(δ/γ) value of 0.16C% peritectic steel was 17 μm. With increasing carbon content, the contraction degree of the δ→γ transformation decreased, and the value of the surface roughness Ra(δ/γ) declined. Therefore, surface roughness can characterize the contraction degree of the δ→γ transformation in the initial solidification process of peritectic steel under the condition of a large cooling rate.

Effect of Particle Size on the Lamellar Pore Microstructure of Porous Al2O3 Ceramics Fabricated by the Unidirectional Freezing

2012 ◽  
Vol 184-185 ◽  
pp. 818-825 ◽  
Author(s):  
Xiao Yong Zhang ◽  
Yan Zhang ◽  
Dou Zhang
Keyword(s):  
Freezing Temperature ◽  
Porous Ceramics ◽  
Solid Loading ◽  
Freezing Process ◽  
Pore Channel ◽  
Nucleation Sites ◽  
Lower Porosity ◽  
Effect Of Particle Size ◽  
Pore Microstructure ◽  
Directional Freezing

Porous Al2O3 ceramics with a lamellar pore microstructure have been fabricated by a directional freezing process using the micro-sized and nano-sized Al2O3 powders. At the same solid loading and freezing temperature, compared with the suspensions of micro-sized Al2O3, the porous ceramics prepared from the suspensions of nano-sized Al2O3 had the narrower lamellar pore channels and thicker channel walls, which were caused by the higher viscosity, stronger inter-particle attraction and more ice nucleation sites in the nano-sized Al2O3 suspensions. For both types of Al2O3 at a specific solid loading, with the increasing of freezing temperature, the wider pore channels and thinner channel walls were observed. These tendencies were weaker by using the nano-sized Al2O3 . The above results show the lower porosity in the ceramics using the nano-sized Al2O3. However, due to the higher sintering activity for the smaller particles, the pore channel walls by using the nano-sized Al2O3 was denser than using the micro-sized Al2O3, leading to the higher mechanical strength of ceramics.

Cooling rate dependence of solidification for liquid aluminium: a large-scale molecular dynamics simulation study

2016 ◽  
Vol 18 (26) ◽  
pp. 17461-17469 ◽  
Author(s):  
Z. Y. Hou ◽  
K. J. Dong ◽  
Z. A. Tian ◽  
R. S. Liu ◽  
Z. Wang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Cooling Rate ◽  
Simulation Study ◽  
Large Scale ◽  
Solidification Process ◽  
Molecular Dynamics Method ◽  
Dynamics Simulation ◽  
Liquid Aluminium ◽  
Dynamics Method

The effect of the cooling rate on the solidification process of liquid aluminium is studied using a large-scale molecular dynamics method.

Effect of Drying on Porous Characteristics of Orange Peel

2016 ◽  
Vol 12 (9) ◽  
pp. 921-928 ◽  
Author(s):  
Cansu Tamer ◽  
Asli Isci ◽  
Naciye Kutlu ◽  
Ozge Sakiyan ◽  
Serpil Sahin ◽  
...  
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Orange Peel ◽  
Sem Analysis ◽  
Shrinkage Porosity ◽  
Process Conditions ◽  
Third Order ◽  
Strong Negative Correlation ◽  
Different Temperatures

Abstract The purpose of the study was to determine the effects of different temperatures (40, 50 and 60 °C) and air velocities (1 and 2 m/s) on shrinkage, porosity, pore size distribution, color and microstructure of orange peel. Empirical models were also proposed to predict shrinkage and porosity as a function of moisture. A strong negative correlation was determined between moisture and shrinkage. Air temperature had no significant impact on the final shrinkage and porosity values. During drying, porosity of the samples first increased until a critical value, at which point further decrease in moisture resulted in collapse of pores. The porosity of the orange peel was correlated with moisture by a third-order polynomial. Pore size distribution curve of raw sample showed two major peaks, a wider and a sharper peak at around 19.8 and 7.18 μm, respectively. After drying, the peaks became shorter and the curve shifted to the left, indicating that the amount of pores and their diameter decreased. The SEM analysis revealed that at extreme process conditions, the orange peel surface was cracked and the characteristic distribution of the waxy components was obstructed.

scholarly journals On the Primary Solidification of Compacted Graphite Iron: Microstructure Evolution during Isothermal Coarsening

2018 ◽  
Vol 925 ◽  
pp. 90-97 ◽  
Author(s):  
Juan Carlos Hernando ◽  
Attila Diószegi
Keyword(s):  
Cast Iron ◽  
Morphological Evolution ◽  
Solidification Process ◽  
Primary Phase ◽  
Eutectic Solidification ◽  
Spheroidal Graphite ◽  
Cube Root ◽  
Compacted Graphite ◽  
Primary Austenite ◽  
Graphite Cast Iron

It is widely accepted that in most commercial hypoeutectic alloys, both static mechanical properties and feeding characteristics during solidification, are extremely linked to the coarseness of the primary phase. It is therefore of critical importance to provide tools to control and predict the coarsening process of the dendritic phase present in hypoeutectic melts. The characterization of the primary phase, a product of the primary solidification, has traditionally been neglected when compared to the eutectic solidification characterization in cast iron investigations. This work presents the morphological evolution of the primary austenite present in a hypoeutectic compacted graphite cast iron (CGI) under isothermal conditions. To that purpose, a base spheroidal graphite cast iron (SGI) material with high Mg content is re-melted in a controlled atmosphere and reversed into a CGI melt by controlling the Mg fading. An experimental isothermal profile is applied to the solidification process of the experimental alloy to promote an isothermal coarsening process of the primary austenite dendrite network during solid and liquid coexistence. Through interrupted solidification experiments, the primary austenite is preserved and observed at room temperature. By application of stereological relations, the primary phase and its isothermal coarsening process are characterized as a function of the coarsening time applied. The microstructural evolution observed in the primary austenite in CGI and the measured morphological parameters show a similar trend to that observed for lamellar graphite cast iron (LGI) in previous investigations. The modulus of the primary austenite, Mγ, and the nearest distance between the centre of gravity of neighbouring austenite particles, Dγ, followed a linear relation with the cube root of coarsening time.

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