Detection of Dendrite Coherency Temperature of Aluminum Alloys Using Single Thermocouple Technique
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M. Djurdjevic
Abstract
The dendrite coherency point (DCP) temperature refers to the state of a solidifying alloy at which a coherent dendrite network is established during the formation of grains. There are three main approaches for detection of DCP: (i) the thermal analysis method, (ii) mechanical (or rheological) technique and (iii) physical method based on the thermal diffusivity measurement technique.
There are two basic variants of the thermal analysis method. In the late 1980's Bäckerud developed a method that utilizes two thermocouples. The DCP is determined by identifying the point of minimum temperature difference at the δT curve (TW–TC). Recently, has been revealed that utilization of the first derivative curve (dT/dt) plotted versus temperature also allows for analysis of the α-Al dendrite nucleation and growth characteristics and consequently determination of the DCT. This paper will illustrate that the dendrite coherency temperature could be identified by the 1st derivative curve (the one-thermocouple method) with the same accuracy as well as by using two thermocouples technique.
Kurzfassung
Die Temperatur des Dendritenkohärenzpunktes (DCP) bezieht sich auf den Zustand einer erstarrenden Legierung, bei der während der Kornbildung ein kohärentes Dendritennetzwerk entstanden ist. Für die Ermittlung des DCP gibt es drei Hauptansätze: (i) die Methode der Thermoanalyse, (ii) ein mechanisches (bzw. rheologisches) Verfahren und (iii) die physikalische Methode, die auf dem Verfahren der Messung der Temperaturleitfähigkeit beruht.
Es gibt zwei Varianten der Thermoanalysemethode. In den späten 80er Jahren entwickelte Bäckerud eine Methode, bei der zwei Thermoelemente eingesetzt werden. Der DCP wird über die Bestimmung des Punktes des minimalen Temperaturunterschieds der δT-Kurve (TW–TC) ermittelt. Jüngst wurde entdeckt, dass die Auswertung der ersten, über die Temperatur aufgetragenen Ableitungskurve (dT/dt) gleichsam eine Analyse der α-Al-Dendritkeimbildung und der Wachstumsmerkmale und folglich eine Bestimmung des DCT ermöglicht. Dieser Beitrag zeigt, dass die Dendritenkohärenztemperatur anhand der ersten Ableitungskurve (die Methode mit einem Thermoelement) mit der gleichen Genauigkeit ermittelt werden konnte, wie bei der Methode, die dafür zwei Thermoelemente einsetzt.
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© 2012, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Editorial
- Editorial
- Technical Contributions/Fachbeiträge
- New Ways of Revealing the Microstructures of SiC Materials
- The Materialographic Preparation and Microstructure Characterization of Lithium Ion Accumulators
- Detection of Dendrite Coherency Temperature of Aluminum Alloys Using Single Thermocouple Technique
- Failure Analysis
- Thermal Fatigue Cracks in Gas Turbine Heat Shield Plates
- Meeting Diary/Veranstaltungskalender
- Meeting Diary
Articles in the same Issue
- Contents/Inhalt
- Contents
- Editorial
- Editorial
- Technical Contributions/Fachbeiträge
- New Ways of Revealing the Microstructures of SiC Materials
- The Materialographic Preparation and Microstructure Characterization of Lithium Ion Accumulators
- Detection of Dendrite Coherency Temperature of Aluminum Alloys Using Single Thermocouple Technique
- Failure Analysis
- Thermal Fatigue Cracks in Gas Turbine Heat Shield Plates
- Meeting Diary/Veranstaltungskalender
- Meeting Diary
