Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo)
Apart from the reported transition from the fibrous morphology in NiAl-34Cr to lamellae by adding 0.6 at.% Mo, further morphology transformations along the eutectic trough in the NiAl-(Cr,Mo) alloys were observed. Compositions with at least 10.3 at.% Cr have lamellar morphology while the first tende...
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MDPI AG
2020-07-01
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| Online Access: | https://www.mdpi.com/2075-4701/10/7/961 |
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| author | Camelia Gombola Alexander Kauffmann Golnar Geramifard Malte Blankenburg Martin Heilmaier |
| author_facet | Camelia Gombola Alexander Kauffmann Golnar Geramifard Malte Blankenburg Martin Heilmaier |
| author_sort | Camelia Gombola |
| collection | DOAJ |
| description | Apart from the reported transition from the fibrous morphology in NiAl-34Cr to lamellae by adding 0.6 at.% Mo, further morphology transformations along the eutectic trough in the NiAl-(Cr,Mo) alloys were observed. Compositions with at least 10.3 at.% Cr have lamellar morphology while the first tendency to fiber formation was found at 9.6 at.% Cr. There is a compositional range, where both lamellae and fibers are present in the microstructure and a further decrease in Cr to 1.8at.% Cr results in fully fibrous morphology. Alongside these morphology changes of the (Cr,Mo)<sub>ss</sub> reinforcing phase, its volume fraction was found to be from 41 to 11 vol.% confirming the trend predicted by the CALPHAD approach. For mixed morphologies in-situ X-ray diffraction experiments performed between room and liquidus temperature accompanied by EDX measurements reveal the formation of a gradient in composition for the solid solution. A new Mo-rich NiAl-9.6Cr-10.3Mo alloy clearly shows this effect in the as-cast state. Moreover, crystallographic orientation examination yields two different types of colonies in this composition. In the first colony type, the orientation relationship between NiAl matrix and (Cr,Mo)<sub>ss</sub> reinforcing phase was <inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mn>100</mn> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula><sub>NiAl</sub>||<inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mn>100</mn> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula><sub>Cr,Mo</sub> and <inline-formula> <math display="inline"> <semantics> <mrow> <mo>〈</mo> <mn>100</mn> <mo>〉</mo> </mrow> </semantics> </math> </inline-formula><sub>NiAl</sub>||<inline-formula> <math display="inline"> <semantics> <mrow> <mo>〈</mo> <mn>100</mn> <mo>〉</mo> </mrow> </semantics> </math> </inline-formula><sub>Cr,Mo</sub>. An orientation relationship described by a rotation of almost 60° about <inline-formula> <math display="inline"> <semantics> <mrow> <mo>〈</mo> <mn>111</mn> <mo>〉</mo> </mrow> </semantics> </math> </inline-formula> was found in the second colony type. In both cases, no distinct crystallographic plane as phase boundary was observed. |
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| spelling | doaj.art-ee0638cfe0b84bbeaa56dc5989b738ee2023-11-20T06:58:11ZengMDPI AGMetals2075-47012020-07-0110796110.3390/met10070961Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo)Camelia Gombola0Alexander Kauffmann1Golnar Geramifard2Malte Blankenburg3Martin Heilmaier4Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Engelbert-Arnold-Str. 4, 76131 Karlsruhe, GermanyInstitute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Engelbert-Arnold-Str. 4, 76131 Karlsruhe, GermanyInstitute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Engelbert-Arnold-Str. 4, 76131 Karlsruhe, GermanyInstitute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, GermanyInstitute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Engelbert-Arnold-Str. 4, 76131 Karlsruhe, GermanyApart from the reported transition from the fibrous morphology in NiAl-34Cr to lamellae by adding 0.6 at.% Mo, further morphology transformations along the eutectic trough in the NiAl-(Cr,Mo) alloys were observed. Compositions with at least 10.3 at.% Cr have lamellar morphology while the first tendency to fiber formation was found at 9.6 at.% Cr. There is a compositional range, where both lamellae and fibers are present in the microstructure and a further decrease in Cr to 1.8at.% Cr results in fully fibrous morphology. Alongside these morphology changes of the (Cr,Mo)<sub>ss</sub> reinforcing phase, its volume fraction was found to be from 41 to 11 vol.% confirming the trend predicted by the CALPHAD approach. For mixed morphologies in-situ X-ray diffraction experiments performed between room and liquidus temperature accompanied by EDX measurements reveal the formation of a gradient in composition for the solid solution. A new Mo-rich NiAl-9.6Cr-10.3Mo alloy clearly shows this effect in the as-cast state. Moreover, crystallographic orientation examination yields two different types of colonies in this composition. In the first colony type, the orientation relationship between NiAl matrix and (Cr,Mo)<sub>ss</sub> reinforcing phase was <inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mn>100</mn> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula><sub>NiAl</sub>||<inline-formula> <math display="inline"> <semantics> <mrow> <mrow> <mo>(</mo> <mrow> <mn>100</mn> </mrow> <mo>)</mo> </mrow> </mrow> </semantics> </math> </inline-formula><sub>Cr,Mo</sub> and <inline-formula> <math display="inline"> <semantics> <mrow> <mo>〈</mo> <mn>100</mn> <mo>〉</mo> </mrow> </semantics> </math> </inline-formula><sub>NiAl</sub>||<inline-formula> <math display="inline"> <semantics> <mrow> <mo>〈</mo> <mn>100</mn> <mo>〉</mo> </mrow> </semantics> </math> </inline-formula><sub>Cr,Mo</sub>. An orientation relationship described by a rotation of almost 60° about <inline-formula> <math display="inline"> <semantics> <mrow> <mo>〈</mo> <mn>111</mn> <mo>〉</mo> </mrow> </semantics> </math> </inline-formula> was found in the second colony type. In both cases, no distinct crystallographic plane as phase boundary was observed.https://www.mdpi.com/2075-4701/10/7/961eutecticmicrostructureorientation relationshipsegregationdiffraction |
| spellingShingle | Camelia Gombola Alexander Kauffmann Golnar Geramifard Malte Blankenburg Martin Heilmaier Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo) Metals eutectic microstructure orientation relationship segregation diffraction |
| title | Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo) |
| title_full | Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo) |
| title_fullStr | Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo) |
| title_full_unstemmed | Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo) |
| title_short | Microstructural Investigations of Novel High Temperature Alloys Based on NiAl-(Cr,Mo) |
| title_sort | microstructural investigations of novel high temperature alloys based on nial cr mo |
| topic | eutectic microstructure orientation relationship segregation diffraction |
| url | https://www.mdpi.com/2075-4701/10/7/961 |
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