Effect of Complex Inclusion Particles on the Solidification Structure of Fe-Ni-Mn-Mo Alloy

The effect of combinations of several deoxidizers, i.e., Mg-Al, Mg-Ti, Al-Ti, and Ce-Al, on the solidification structure of Fe-2 mass pct Ni-1 mass pct Mn-1 mass pct Mo alloy melt was investigated using a melt sampling and quenching method. Using this method, we evaluated the catalytic potency of several complex inclusion particles by taking the inclusion evolution process into account. Fine equiaxed crystals were obtained in the Mg-Ti-deoxidized steel wherein the MgO(MgAl₂O₄)-TiN complex compounds formed. However, the longer the holding time at high temperatures, the larger the fraction of Ti₂O₃, and very fine TiN formed because of microsegregation during solidification, resulting in poor equiaxed crystals. When the steel was deoxidized with Mg-Al, the initial structure was dominantly columnar. However, the longer the holding time, the larger the fraction of MgAl₂O₄ spinel, resulting in the formation of fine equiaxed crystals. Ce-Al complex deoxidation provided a relatively small portion of equiaxed crystals, whereas Ti-Al deoxidation produced the fewest equiaxed crystals because of the formation of alumina. The effectiveness of each inoculant particle for the crystallization of the primary δ-iron was explained well by the lattice disregistry concept.

Appendix

To illustrate the calculation of disregistry, we provide examples for several oxide inclusions nucleating TiN.[21] In these examples, the MgAl₂O₄ spinel, Al₂O₃, MgO, and Ti₂O₃ were selected as nucleation sites for TiN. The crystallographic relationships of each case are illustrated in Figures A1 and A2, and the corresponding parameters for Eq. [4] are listed in Table IV.

Fig. A1

The crystallographic relationship at the interface between (100)TiN and (100)MgAl₂O₄ (a), and between (100)TiN and (100)MgO (b)

Fig. A2

The crystallographic relationship at the interface between (100)TiN and (0001)Ti₂O₃ (a), and between (100)TiN and (0001)Al₂O₃ (b)

Table IV Parameters Used for the Disregistry Calculations

Case I; MgAl₂O₄(100)//TiN(100)

As shown in Figure A1(a), the (100) plane of TiN is superimposed on the (100) plane of spinel. The three lowest-index directions of TiN and MgAl₂O₄ are $\left[ {\overline{1} 00} \right]$, $\left[ {\overline{1} 10} \right]$ and $\left[ {010} \right]$. The distances along these directions are given in Table IV. In accordance with Eq. [4], the disregistry equation for Case 1 was written as follows:

$$ \delta_{{\left( {100} \right)_{\text{TiN}} }}^{{\left( {100} \right)_{{{\text{MgAl}}_{ 2} {\text{O}}_{ 4} }} }} = \frac{1}{3}\left( {\frac{{\left| {(d_{{\left[ {\overline{1} 00} \right]_{{{\text{MgAl}}_{ 2} {\text{O}}_{ 4} }} }} \cos \theta ) - d_{{[\overline{1} 00]_{\text{TiN}} }} } \right|}}{{d_{{[\overline{1} 00]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[\overline{1} 10]_{{{\text{MgAl}}_{ 2} {\text{O}}_{ 4} }} }} \cos \theta ) - d_{{[\overline{1} 10]_{\text{TiN}} }} } \right|}}{{d_{{[\overline{1} 10]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[010]_{{{\text{MgAl}}_{ 2} {\text{O}}_{ 4} }} }} \cos \theta ) - d_{{[010]_{\text{TiN}} }} } \right|}}{{d_{{[010]_{\text{TiN}} }} }}} \right) \times 100 = \frac{1}{3}\left( {\frac{{\left| {4.098 - 4.308} \right|}}{4.308} + \frac{{\left| {2.897 - 3.046} \right|}}{3.046} + \frac{{\left| {4.098 - 4.308} \right|}}{4.308}} \right) \times 100 = 4.88\,{\text{pct}}$$

Case II; MgO(100)//TiN(100)

As shown in Figure A1(b), the (100) plane of TiN is superimposed on the (100) plane of MgO. Using a similar analysis to that used in Case I, Eq. [4] was written as follows:

$$ \delta_{{(100)_{\text{TiN}} }}^{{(100)_{\text{MgO}} }} = \frac{1}{3}\left( {\frac{{\left| {(d_{{[\overline{1} 00]_{\text{MgO}} }} \cos \theta ) - d_{{[\overline{1} 00]_{\text{TiN}} }} } \right|}}{{d_{{[\overline{1} 00]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[\overline{1} 10]_{\text{MgO}} }} \cos \theta ) - d_{{[\overline{1} 10]_{\text{TiN}} }} } \right|}}{{d_{{[\overline{1} 10]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[010]_{\text{MgO}} }} \cos \theta ) - d_{{[010]_{\text{TiN}} }} } \right|}}{{d_{{[010]_{\text{TiN}} }} }}} \right) \times 100 = \frac{1}{3}\left( {\frac{{\left| {4.310 - 4.308} \right|}}{4.308} + \frac{{\left| {3.048 - 3.046} \right|}}{3.046} + \frac{{\left| {4.310 - 4.308} \right|}}{4.308}} \right) \times 100 = 0.053\,{\text{pct}} $$

Case III; Ti₂O₃(0001)//TiN(100)

Because the lattice disregistry is 23.46 pct for the (110) plane of TiN and 48.36 pct for the (111) plane of TiN, the (100) of TiN is superimposed on the (0001) plane of Ti₂O₃, as shown in Figure A2(a). Equation [4] was therefore written as:

$$ \delta_{{(100)_{\text{TiN}} }}^{{(0001)_{{{\text{Ti}}_{ 2} {\text{O}}_{ 3} }} }} = \frac{1}{3}\left( {\frac{{\left| {(d_{{[\overline{1} 2\overline{1} 0]_{{{\text{Ti}}_{ 2} {\text{O}}_{ 3} }} }} \cos \theta ) - d_{{[010]_{\text{TiN}} }} } \right|}}{{d_{{[001]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[\overline{2} 110]_{{{\text{Ti}}_{ 2} {\text{O}}_{ 3} }} }} \cos \theta ) - d_{{[011]_{\text{TiN}} }} } \right|}}{{d_{{[1\overline{1} 1]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[\overline{1} 010]_{{{\text{Ti}}_{ 2} {\text{O}}_{ 3} }} }} \cos \theta ) - d_{{[001]_{\text{TiN}} }} } \right|}}{{d_{{[1\overline{1} 0]_{\text{TiN}} }} }}} \right) \times 100 = \frac{1}{3}\left( {\frac{{\left| {3.146 - 4.308} \right|}}{4.308} + \frac{{\left| {3.039 - 3.046} \right|}}{3.046} + \frac{{\left| {5.225 - 4.308} \right|}}{4.308}} \right) \times 100 = 16.17\,{\text{pct}}$$

Case IV; Al₂O₃(0001)//TiN(100)

Because the lattice disregistry of the (110) plane of TiN is 23.7 pct and that of the (111) plane of TiN is 51.7 pct, the (100) plane of TiN is superimposed on the (0001) of Al₂O₃, as shown in Figure A2(b). Using a similar analysis as in Case III yielded the following Eq. [4]:

$$ \delta_{{(100)_{\text{TiN}} }}^{{(0001)_{{{\text{Al}}_{ 2} {\text{O}}_{ 3} }} }} = \frac{1}{3}\left( {\frac{{\left| {(d_{{[\overline{1} 2\overline{1} 0]_{{{\text{Al}}_{ 2} {\text{O}}_{ 3} }} }} \cos \theta ) - d_{{[010]_{\text{TiN}} }} } \right|}}{{d_{{[010]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[\overline{2} 110]_{{{\text{Al}}_{ 2} {\text{O}}_{ 3} }} }} \cos \theta ) - d_{{[011]_{\text{TiN}} }} } \right|}}{{d_{{[011]_{\text{TiN}} }} }} + \frac{{\left| {(d_{{[\overline{1} 010]_{{{\text{Al}}_{ 2} {\text{O}}_{ 3} }} }} \cos \theta ) - d_{{[001]_{\text{TiN}} }} } \right|}}{{d_{{[001]_{\text{TiN}} }} }}} \right) \times 100 = \frac{1}{3}\left( {\frac{{\left| {2.905 - 4.308} \right|}}{4.308} + \frac{{\left| {2.806 - 3.046} \right|}}{3.046} + \frac{{\left| {4.825 - 4.308} \right|}}{4.308}} \right) \times 100 = 17.48\,{\text{pct}} $$