I would like to obtain time temperature transformation (TTT) and / or continuous heating transformation (CHT) diagrams by Differential Scanning Calorimetry (DSC). As it clear by DSC we can seatmate kinetic of reaction just in a certain condition. In order to have more accurate way to talking about kinetic of reaction in a broad condition I need these diagrams. Would you please help me to find methodology?
Regards
Dear Ali,
in our lab we developed exactly the meathods your looking for. You can find the related publications at my proflie. For Continuous cooling precipitation or transfomation diagrams see first: Milkereit et al. 2009 Recording of continous cooling precipitation diagrams of aluminiumalloys TCA 492 (2009) 73-78
for continuous heating dissolution and precipitation diagrams basically teh same methods works fine, see: Milkereit et al 2012 continuous heating dissolution diagrams of Al alloys proceedings ICAA13-095
besides, for isothermal transformation daigrams can be obtained using the procedure described in: Milkereit, Benjamin; Giersberg, Lydia; Kessler, Olaf; Schick, Christoph (2014): Isothermal Time-Temperature-Precipitation Diagram for an Aluminum Alloy 6005A by In Situ DSC Experiments. In: Materials 7 (4), S. 2631-2649. DOI: 10.3390/ma7042631.
If you have some questions just write me.
Best regards,
Benjamin
I think, you can obtain the TTT diagram by using a transformation peak. For exemple, in the case of polymers, if you study the crystallization from melt, at the beginning of the peak (onset point), there is no transformation and at the end the transformation is completed (100%), Then by calculating the area under the corresponding peak you can then plot the transformation as a function of time. For a constant temperature (crystallization is isotherm), you have time, temperature and transformation.
We used time-temperature superposition (TTS) for many cases biopolymer and polymer where inbuilt software is there. If you have rheometer you can try there. It will be easy.
Dear Ali,
in our lab we developed exactly the meathods your looking for. You can find the related publications at my proflie. For Continuous cooling precipitation or transfomation diagrams see first: Milkereit et al. 2009 Recording of continous cooling precipitation diagrams of aluminiumalloys TCA 492 (2009) 73-78
for continuous heating dissolution and precipitation diagrams basically teh same methods works fine, see: Milkereit et al 2012 continuous heating dissolution diagrams of Al alloys proceedings ICAA13-095
besides, for isothermal transformation daigrams can be obtained using the procedure described in: Milkereit, Benjamin; Giersberg, Lydia; Kessler, Olaf; Schick, Christoph (2014): Isothermal Time-Temperature-Precipitation Diagram for an Aluminum Alloy 6005A by In Situ DSC Experiments. In: Materials 7 (4), S. 2631-2649. DOI: 10.3390/ma7042631.
If you have some questions just write me.
Best regards,
Benjamin
Dear Ali
my research is about a new DS Ni-based superalloy and i have obtained TTT diagram for it. you must note that in major of alloys and multiphase materials which have non-equilibrium phase, some phases may form after long time. in this condition DSC analysis (which is short time test) could not illustrate you that phase effect.
Best regards,
Mohammad
Dear Ali,
The sensitivity of the DSC/DTA in capturing the characteristics temperature for minor phases is bit lower. Still you can firmup your composition of the alloy being analysed in DSC. By systematic variation of the one of the elements in the composition, with constant heating rate (normally 20degC/min) and cooling rate, characteristics temperatures can be found out for the each composition of the test alloy. Now you have the elemental concentration and temperature data for plotting the phase diagram. When you opt for higher heating rates, you may have to be cautious in the data. By integrating the DSC curve, you will be getting the heat of fusion/latent heat of fusion. But another option is Gleeble method.
Dear Colleges,
I like to comment on the latter two answers.
First, if you chose the proper DSC device, slow scanning is possible with excellent results (i. e. use CALVET-type DSC sensors for slow rates). Recently we developed a new DSC method which we have proven so far to work perfectly for cooling of an aluminium alloy from 540 °C to room temperature with 0.0001 K/s, which takes a duration of 60 days! A related paper will be published in Thermochimica Acta soon. In previous publications we already showed that cooling duration up to two weeks are easily possible for the same temperature difference. The choice of scanning rate in heating or cooling is just very much dependent on the particular device you’re utilizing. In our lab in Rostock today we cover a scanning rate range between about 0.0001 K/s up to 10.000 K/s for metallic alloys or even up to some MK/s for polymers. To obtain this dynamic range e. g. for metallic samples we utilize five different types of DSCs.
Regarding the latest answer of Manikandan Sgk, the sensitivity of a DSC device is strictly related to the proper choice of all parameters. The heat flow signal is mainly depended on Sample mass and Scanning rate.
Hence you’ve to ensure, that the sample mass is appropriate for the scanning rate you like to measure. Of course the adjustment of sample mass only works with choosing different DSC devices.
If both is chosen reasonably you can obtain highly sensitive measurements. We showed in 2009, that the detection limit for precipitation reactions in aluminium alloys is 0.1 J/g – which is extremely small. This detection limit again could only be reached utilizing the appropriate experimental setup – i. e. choosing the correct DSC and measuring the excess heat flow, evaluating the excess specific heat capacity. Therefor you have to measure the sample you’re interested in against an inert reference sample. Besides the baseline-measurement must be an inert reference versus an inert reference.
However, just have a look in our publications. You might just not exactly know what your DSC is able to do ;)
Best regards,
Benjamin
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