Influencing parameters for grain growth

ripening phenomena, dislocations, grainboundary topology
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Moritz
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Influencing parameters for grain growth

Post by Moritz » Mon Jan 31, 2022 9:53 am

Hello everyone!

I recently added grain growth in the solid state to a solidification simulation, which I use to simulate the solidification after the LPBF process.

Unfortunately, I currently oberserve grain growth, which leads to very big grains in a matter of microseconds. The simulation already includes Zener pinning and my time temperature profile is based on the real process.

Does anyone have suggestions about more parameters that I could use to slow down or influence the grain growth in general?

I am looking forward to you replies.

Best regards,

Moritz

Bernd
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Re: Influencing parameters for grain growth

Post by Bernd » Mon Jan 31, 2022 10:28 am

Dear Moritz,

The kinetics of grain growth (i.e. interaction between grains of the same phase) essentially depend on the interface mobility and the interface energy. In contrary to the case of solidification where we want to achieve diffusion limited growth kinetics (and assume the physical interface mobility to be huge), grain growth is really controlled by interface mobility. To get the correct interface mobility values (and especially its temperature dependence), you need to have experimental grain growth data. A typical value for temperatures below the solidification range would be 1.E-5 cm**4/(Js). Which value did you use?

Bernd

Moritz
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Re: Influencing parameters for grain growth

Post by Moritz » Tue Feb 08, 2022 10:00 am

Hi Bernd,

thanks again for your helpful and quick reply!

The value which we used until now was propably way off (1 cm**4/(Js)), but did not come to our attention until now.

The value you mentioned is typical for temperatures below the solidification range. As ThermoCalc does not seem to have the possibility to calculate interface mobility, do you know ways to determine this value for different temperatures and different alloys?

Best regards,

Moritz

Bernd
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Joined: Mon Jun 23, 2008 9:29 pm

Re: Influencing parameters for grain growth

Post by Bernd » Tue Feb 08, 2022 12:49 pm

Hi Moritz,

Values for the interface mobility are difficult to get. They must either be measured for the specific alloy (under extremely pure conditions) or simulated with atomistic methods (e.g. molecular dynamics). Simulations have mostly been done for pure substances only.

My advice would be to try to calibrate the interface mobility according to the experimental data you have for your alloy (e.g. grain coarsening). But I have to admit that I never took a really strong effort searching the literature...

Bernd

Moritz
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Re: Influencing parameters for grain growth

Post by Moritz » Thu Feb 10, 2022 1:14 pm

Hi Bernd,

thanks for the advice!

We tried several values and are confident to move on with one of them.

Best regards,
Moritz

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