Effects of Melt Treatment on Dendrite Coherency of A357 Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 3886-3890
Author(s):  
Zhong Wei Chen ◽  
Pei Chen ◽  
Li Fan
Keyword(s):  
Thermal Analysis ◽  
Growth Rate ◽  
Cooling Rate ◽  
Solid Fraction ◽  
Dendrite Growth ◽  
A357 Alloy ◽  
Dendrite Coherency Point ◽  
Melt Treatment ◽  
Coherency Point ◽  
Dendrite Coherency

The Dendrite Coherency Point (DCP) of A357 alloy was determined after different melt treatments by double thermocouples, and the coherency solid fraction (fscoh) was calculated by thermal analysis. The results of dendrite coherency properties show that fscoh values increase with increased cooling rate for A357 alloy. For A357 alloys, fscoh values increase after grain refined and melt superheat treatment. The coherency point was found to be dependent on not only the morphology of the dendrites but also the dendrite growth rate.

Influence of Cooling Rate on the Size of the Precipitates and Thermal Characteristic of Al-Si Cast Alloys

2006 ◽  
Vol 15-17 ◽  
pp. 59-64 ◽  
Author(s):  
Rafal Maniara ◽  
Leszek Adam Dobrzański ◽  
Jerry Sokolowski ◽  
Wojciech Kasprzak ◽  
Witold T. Kierkus
Keyword(s):  
Cooling Rate ◽  
Solidus Temperature ◽  
Thermal Characteristic ◽  
Solidification Process ◽  
Crystallization Curve ◽  
Dendrite Coherency Point ◽  
Cast Alloys ◽  
Main Observation ◽  
Coherency Point ◽  
Work Effect

In this work effect of cooling rate on the size of the grains, SDAS, β phases and thermal characteristic results of Al-Si cast alloys have been described. The solidification process was studied using the cooling and crystallization curve at cooling rate ranging from 0,1 °Cs-1 up to 1 °Cs-1. The main observation made from this work was that when cooling rate is increased the aluminum dendrites nucleation temperature and solid fraction at the dendrite coherency point increases, which implies that mass feeding is extended. In addition to that, it was observed that solidus temperature and size of the β phases decreases when cooling rate increases. Investigations were showed, that the thermal modification could be quantitatively assessed by analysis of the crystallization curve.

scholarly journals The Determination of Dendrite Coherency Point Characteristics Using Three New Methods for Aluminum Alloys

2018 ◽  
Vol 8 (8) ◽  
pp. 1236 ◽  
Author(s):  
Iban Gómez ◽  
Ester Viteri ◽  
Jessica Montero ◽  
Mile Djurdjevic ◽  
Gerhard Huber
Keyword(s):  
Cooling Curves ◽  
The Third ◽  
New Methods ◽  
Dendrite Coherency Point ◽  
Zero Line ◽  
Coherency Point ◽  
Dendrite Coherency ◽  
The Impact ◽  
Crossing Point

The aim of this work is to give an overview of existing methods and to introduce three new methods for the determination of the Dendrite Coherency Point (DCP) for AlSi10Mg alloys, as well as to compare the acquired values of DCP based on a thermal analysis and on the analysis of cooling curves working with only one thermocouple. Additionally, the impact of alloying and contaminant elements on the DCP will be also studied. The first two proposed methods employ the higher order derivatives of the cooling curves. The DCP was determined as the crossing point of the second and third derivative curves plotted versus time (method 1) or that of the temperature (method 2) with the zero line just after the maximum liquidus temperature. The third proposed method is based on the determination of the crossing point of the third solid fraction derivative curve with the zero line, corresponding to a minimum of the second derivative. A Taguchi design for the experiments was developed to study the DCP values in the AlSi10Mg alloy. The DCP temperature values of the test alloys were compared with the DCP temperatures predicted by the previous methods and the influence of the major and minor alloying elements and contaminants over the DCP. The new processes obtained a correlation factor r2 from 0.954 and 0.979 and a standard deviation from 1.84 to 2.6 °C. The obtained correlation values are higher or similar than those obtained using previous methods with an easier way to define the DCP, allowing for a better automation of the accuracy of DCP determination. The use of derivative curves plotted versus temperature employed in the last two proposed methods, where the test samples did not have an influence over the registration curves, is proposed to have a better accuracy than those of the previously described methods.

Phase Evaluation of Pure Mg, Mg-1Ca and Mg-1Ca-3Zn ‎Alloys by Thermal Analysis Used in ‎Medical Applications

2014 ◽  
Vol 606 ◽  
pp. 93-97
Author(s):  
Hamid Reza Bakhsheshi-Rad ◽  
Esah Hamzah ◽  
M.H. Idris ◽  
S. Farahany ◽  
A. Fereidouni‎
Keyword(s):  
Thermal Analysis ◽  
Microstructural Analysis ◽  
Intermetallic Phase ◽  
Phase Identification ◽  
X Ray ◽  
Dendrite Coherency Point ◽  
Coherency Point ◽  
Phase Evaluation ◽  
Mg Melt ◽  
Significant Attention

In this research paper phase identification was conducted based on the thermal and microstructural analysis of pure Mg, binary ‎Mg-Ca and ternary Mg-Ca-Zn alloys which have been received significant attention to be used as biodegradable implants. ‎Thermal analysis results show that nucleation temperature of primary Mg decreased and solidification range expanded with ‎adding Ca and Zn to the Mg melt. Moreover, characteristics temperatures of intermetallic phase assess for Mg-1Ca and Mg-‎‎1Ca-3Zn alloys. Microstructural evolutions of specimens were characterized by optical microscopy, scanning electron ‎microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). The result revealed that the identification of Mg2Ca and Ca2Mg6Zn3‎intermetallic phases by thermal analysis which were also detected by EDS. Furthermore with addition of Ca and Zn elements, the ‎coherency time increased while, the fraction of primary α-Mg at dendrite coherency point (fαDCP) decreased.‎

scholarly journals Effect of grain refinement on the microstructure, dendrite coherency and porosity of AZ91E magnesium alloy

2021 ◽  
Author(s):  
Mihai Vlasceanu
Keyword(s):  
Magnesium Alloy ◽  
Grain Refinement ◽  
Growth Mechanism ◽  
Solid Fraction ◽  
Dendrite Growth ◽  
Dendritic Morphology ◽  
Al Alloys ◽  
Mg Alloys ◽  
Grain Refiner ◽  
Dendrite Coherency

Magnesium (Mg) alloys present a promising alternative to aluminum (Al) alloys in lightweight applications. However, relative to Al alloys, Mg alloys have poor castability. Castability is influenced significantly by the dendrite coherency point (DCP), which represents the temperature, time, and solid fraction at which an interlocking solid network forms during solidification. An increase in the solid fraction at coherency may improve the castability of the alloy and reduce casting defects such as porosity, hot tears and misruns. A successful method for increasing the solid fraction at the DCP in Al alloys involves the use of grain refiners such as titanium (Ti). However, the influence of Ti refiners on the DCP in Mg alloys has not been thoroughly investigated. The objective of this research was to study the effect of Al-5Ti-1B refiner on the dendrite growth mechanism, DCP and porosity of AZ91E magnesium alloy. This thesis is a pioneering effort in relating the grain refinement effect of Ti on the DCP, coherency solid fraction, and porosity development during the solidification of Mg alloy, AZ91E. It represents an important step in improving the castability of Mg alloys. Varying levels of Al-5Ti1B grain refiner (0.005, 0.05, 0.1, 0.2, and 0.3 wt.% Ti) were added to AZ91E. The effect of Al-5Ti-1B grain refiner on the microstructure and dendrite growth mechanism of AZ91E was investigated. Quench experiments were performed to observe transformations in the dendritic morphology that resulted from the refiner additions. The growth rate and DCP were determined using the rheological method. The changes in porosity levels were determined for the grain refiner additions.

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