Setting for redistribution control & nucleation undercooling
Posted: Thu Jul 08, 2021 11:34 am
Dear Bernd,
I am currently studying the effect of substitutional alloy elements (Ni, Cr and Mn) inhomogeneity on cementite precipitation during cooling of hyper-eutectoid steel.
In the first simulation (see file CarbidePrecipi_at%_cooling_0.4_faceted 8a_ParaTQ) I set the redistribution behaviour of Cr, Ni, and Mn for the austenite/cementite interaction as “ParaTQ”.
The starting temperature of the simulation was 923 K. The cooling rate was equal to 0.4 K/s.
I set the minimum nucleation undercooling for cementite equal to 175 K.
As expected, the nucleus distribution in the domain is dependent on the local value of the substitutional alloy elements. Figure 1 shows the frac3, Cr, Mn and Ni concentrations. The undercooling values for nuclei formed at different times and temperatures during cooling and the overall nuclei undercooling distribution are reported in Figure 2 and Figure 3 respectively. I repeated the simulation changing only the redistribution behaviour of Cr, Ni, and Mn from “ParaTQ” to “Normal”.
Also, in this case, the nucleus distribution in the domain is dependent on the local value of the substitutional alloy elements.
Since the para-equilibrium (PE) condition reduces the value of Acm. (Acm[ortho]=1120 K and Acm[PE]=988 K, calculated by Thermo-calc), I was expecting a higher value of the nucleus undercooling in this simulation (with “Normal” instead of “paraTQ” in the setting of the element redistribution) compared to the previous one. This is not the case as shown in Figure 4 and Figure 5. I also compared the driving force for the austenite to ferrite transformation and I saw that it is higher for the “paraTQ” simulation than for the simulation with “Normal” setting.
Could you please explain the reason for these results?
Best Regards,
Pina
I am currently studying the effect of substitutional alloy elements (Ni, Cr and Mn) inhomogeneity on cementite precipitation during cooling of hyper-eutectoid steel.
In the first simulation (see file CarbidePrecipi_at%_cooling_0.4_faceted 8a_ParaTQ) I set the redistribution behaviour of Cr, Ni, and Mn for the austenite/cementite interaction as “ParaTQ”.
The starting temperature of the simulation was 923 K. The cooling rate was equal to 0.4 K/s.
I set the minimum nucleation undercooling for cementite equal to 175 K.
As expected, the nucleus distribution in the domain is dependent on the local value of the substitutional alloy elements. Figure 1 shows the frac3, Cr, Mn and Ni concentrations. The undercooling values for nuclei formed at different times and temperatures during cooling and the overall nuclei undercooling distribution are reported in Figure 2 and Figure 3 respectively. I repeated the simulation changing only the redistribution behaviour of Cr, Ni, and Mn from “ParaTQ” to “Normal”.
Also, in this case, the nucleus distribution in the domain is dependent on the local value of the substitutional alloy elements.
Since the para-equilibrium (PE) condition reduces the value of Acm. (Acm[ortho]=1120 K and Acm[PE]=988 K, calculated by Thermo-calc), I was expecting a higher value of the nucleus undercooling in this simulation (with “Normal” instead of “paraTQ” in the setting of the element redistribution) compared to the previous one. This is not the case as shown in Figure 4 and Figure 5. I also compared the driving force for the austenite to ferrite transformation and I saw that it is higher for the “paraTQ” simulation than for the simulation with “Normal” setting.
Could you please explain the reason for these results?
Best Regards,
Pina