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Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion
Molybdenum manufactured with laser powder bed fusion (LPBF) has an undesirable coarse-grained, columnar microstructure interspersed with intergranular cracks, high porosity, and poor mechanical strength. These defects result from a combination of the harsh LPBF process conditions and the disadvantag...
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| Published in: | International journal of refractory metals & hard materials 2023-12, Vol.117, p.106384, Article 106384 |
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| container_title | International journal of refractory metals & hard materials |
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| creator | Kaserer, L. Brennsteiner, D. Braun, J. Goettgens, V. Letofsky-Papst, I. Singer, P. Kestler, H. Schafbauer, W. Leichtfried, G. |
| description | Molybdenum manufactured with laser powder bed fusion (LPBF) has an undesirable coarse-grained, columnar microstructure interspersed with intergranular cracks, high porosity, and poor mechanical strength. These defects result from a combination of the harsh LPBF process conditions and the disadvantageous properties of molybdenum, such as its high brittle-ductile transition temperature and low tolerance for oxygen impurities. In order to suppress these defect-forming mechanisms and improve the suitability for LPBF, alloy-side material adjustments with simultaneous process optimization are necessary. In this work, the effect of adjusting Mo by adding 3.5 at.% B is investigated experimentally.
Mo-3.5 at.% B specimens can be produced entirely free of cracks, with a density of 99.8%. The specimens have a microstructure of fine, equiaxed grains with an average grain size of 31 μm and an aspect ratio of 1.3, thus achieving substantial refinement of the otherwise typically coarse-grained columnar, anisotropic microstructure of pure Mo in LPBF. Furthermore, the grains possess a honeycomb-like cellular subgrain structure. This structure is formed through the solute rejection effect of B during the solidification and consists of initially solidified pure α-Mo cells with a cell size |
| doi_str_mv | 10.1016/j.ijrmhm.2023.106384 |
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| fullrecord | <record><control><sourceid>elsevier_cross</sourceid><recordid>TN_cdi_crossref_primary_10_1016_j_ijrmhm_2023_106384</recordid><sourceformat>XML</sourceformat><sourcesystem>PC</sourcesystem><els_id>S0263436823002846</els_id><sourcerecordid>S0263436823002846</sourcerecordid><originalsourceid>FETCH-LOGICAL-c352t-bf3f4fb7e952b598f32d779e2754b63749b67d71f7fc91a8daa530f1e23bcf163</originalsourceid><addsrcrecordid>eNp9kM1KxDAURrNQcBx9Axd5gY5J0ybtRpDBPxhwoa5D0txoSpuUpB0Z8OHNMK5dXfi45-Peg9ANJRtKKL_tN66P49e4KUnJcsRZU52hFSk5KyrGmwt0mVJPCOEtpyv08xaGZYbCebN0YPBnVM7jCNZ5GMHPWHmDDVjoZpyWaYqQkgse5yUdYvDFGIyzLpNjGA7agF9GPCq_WNXNS8z53ik8qAQRT-HbQCx0Du1ybLlC51YNCa7_5hp9PD68b5-L3evTy_Z-V3SsLudCW2YrqwW0danrtrGsNEK0UIq60pyJqtVcGEGtsF1LVWOUqhmxFEqmO0s5W6Pq1NvFkFJ-Tk7RjSoeJCXyaE328mRNHq3Jk7WM3Z0wyLftHUSZOgc-a3Ix-5AmuP8LfgHQIn2z</addsrcrecordid><sourcetype>Aggregation Database</sourcetype><iscdi>true</iscdi><recordtype>article</recordtype></control><display><type>article</type><title>Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion</title><source>ScienceDirect Journals</source><creator>Kaserer, L. ; Brennsteiner, D. ; Braun, J. ; Goettgens, V. ; Letofsky-Papst, I. ; Singer, P. ; Kestler, H. ; Schafbauer, W. ; Leichtfried, G.</creator><creatorcontrib>Kaserer, L. ; Brennsteiner, D. ; Braun, J. ; Goettgens, V. ; Letofsky-Papst, I. ; Singer, P. ; Kestler, H. ; Schafbauer, W. ; Leichtfried, G.</creatorcontrib><description>Molybdenum manufactured with laser powder bed fusion (LPBF) has an undesirable coarse-grained, columnar microstructure interspersed with intergranular cracks, high porosity, and poor mechanical strength. These defects result from a combination of the harsh LPBF process conditions and the disadvantageous properties of molybdenum, such as its high brittle-ductile transition temperature and low tolerance for oxygen impurities. In order to suppress these defect-forming mechanisms and improve the suitability for LPBF, alloy-side material adjustments with simultaneous process optimization are necessary. In this work, the effect of adjusting Mo by adding 3.5 at.% B is investigated experimentally.
Mo-3.5 at.% B specimens can be produced entirely free of cracks, with a density of 99.8%. The specimens have a microstructure of fine, equiaxed grains with an average grain size of 31 μm and an aspect ratio of 1.3, thus achieving substantial refinement of the otherwise typically coarse-grained columnar, anisotropic microstructure of pure Mo in LPBF. Furthermore, the grains possess a honeycomb-like cellular subgrain structure. This structure is formed through the solute rejection effect of B during the solidification and consists of initially solidified pure α-Mo cells with a cell size <1 μm and a honeycomb-like network of an ∼100 nm thick intercellular Mo2B phase completely covering the α-Mo cells. In addition, the formation of boron oxide inclusions, presumably B2O3, with a size of <50 nm within the Mo2B phase, provides an effective mechanism for scavenging oxygen impurities, thus ensuring segregation-free grain boundaries in Mo-3.5 at.% B.
The microstructural modifications substantially improve the mechanical properties. Under appropriate process conditions, with the substrate plate preheating temperature playing a crucial role, a bending strength of 1120 ± 172 MPa and a hardness of 379 ± 24 HV10 at room temperature can be achieved. At a test temperature of 600 °C, an increase in the bending strength to 2265 MPa is observed, and the bending angle simultaneously increases from 2° at room temperature to 35° at 600 °C. These findings indicate that the strength of Mo-3.5 at.% B is limited by the brittle behavior of the material at lower temperatures, at which residual defects are likely to initiate fracture.
[Display omitted]
•An LPBF adapted molybdenum-3.5 at.% boron alloy enables the manufacture of dense, crack-free specimens.•Boron-induced solute rejection during solidification leads to the formation of a fine-grained microstructure with cellular subgrains.•The microstructure of submicron α-Mo cells is surrounded by a closed network of reinforcing, intercellular Mo2B phase.•The formation of nanometer-sized boron oxide inclusions within the Mo2B phase suppresses oxide segregation and grain boundary weakening.•A bending strength of 1120 MPa at room temperature and 2265 MPa at 600 °C is achieved.</description><identifier>ISSN: 0263-4368</identifier><identifier>DOI: 10.1016/j.ijrmhm.2023.106384</identifier><language>eng</language><publisher>Elsevier Ltd</publisher><subject>Alloy development ; Grain refinement ; Laser powder-bed fusion ; Mechanical properties ; Microstructure ; Molybdenum</subject><ispartof>International journal of refractory metals & hard materials, 2023-12, Vol.117, p.106384, Article 106384</ispartof><rights>2023 The Authors</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c352t-bf3f4fb7e952b598f32d779e2754b63749b67d71f7fc91a8daa530f1e23bcf163</citedby><cites>FETCH-LOGICAL-c352t-bf3f4fb7e952b598f32d779e2754b63749b67d71f7fc91a8daa530f1e23bcf163</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,27923,27924</link.rule.ids></links><search><creatorcontrib>Kaserer, L.</creatorcontrib><creatorcontrib>Brennsteiner, D.</creatorcontrib><creatorcontrib>Braun, J.</creatorcontrib><creatorcontrib>Goettgens, V.</creatorcontrib><creatorcontrib>Letofsky-Papst, I.</creatorcontrib><creatorcontrib>Singer, P.</creatorcontrib><creatorcontrib>Kestler, H.</creatorcontrib><creatorcontrib>Schafbauer, W.</creatorcontrib><creatorcontrib>Leichtfried, G.</creatorcontrib><title>Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion</title><title>International journal of refractory metals & hard materials</title><description>Molybdenum manufactured with laser powder bed fusion (LPBF) has an undesirable coarse-grained, columnar microstructure interspersed with intergranular cracks, high porosity, and poor mechanical strength. These defects result from a combination of the harsh LPBF process conditions and the disadvantageous properties of molybdenum, such as its high brittle-ductile transition temperature and low tolerance for oxygen impurities. In order to suppress these defect-forming mechanisms and improve the suitability for LPBF, alloy-side material adjustments with simultaneous process optimization are necessary. In this work, the effect of adjusting Mo by adding 3.5 at.% B is investigated experimentally.
Mo-3.5 at.% B specimens can be produced entirely free of cracks, with a density of 99.8%. The specimens have a microstructure of fine, equiaxed grains with an average grain size of 31 μm and an aspect ratio of 1.3, thus achieving substantial refinement of the otherwise typically coarse-grained columnar, anisotropic microstructure of pure Mo in LPBF. Furthermore, the grains possess a honeycomb-like cellular subgrain structure. This structure is formed through the solute rejection effect of B during the solidification and consists of initially solidified pure α-Mo cells with a cell size <1 μm and a honeycomb-like network of an ∼100 nm thick intercellular Mo2B phase completely covering the α-Mo cells. In addition, the formation of boron oxide inclusions, presumably B2O3, with a size of <50 nm within the Mo2B phase, provides an effective mechanism for scavenging oxygen impurities, thus ensuring segregation-free grain boundaries in Mo-3.5 at.% B.
The microstructural modifications substantially improve the mechanical properties. Under appropriate process conditions, with the substrate plate preheating temperature playing a crucial role, a bending strength of 1120 ± 172 MPa and a hardness of 379 ± 24 HV10 at room temperature can be achieved. At a test temperature of 600 °C, an increase in the bending strength to 2265 MPa is observed, and the bending angle simultaneously increases from 2° at room temperature to 35° at 600 °C. These findings indicate that the strength of Mo-3.5 at.% B is limited by the brittle behavior of the material at lower temperatures, at which residual defects are likely to initiate fracture.
[Display omitted]
•An LPBF adapted molybdenum-3.5 at.% boron alloy enables the manufacture of dense, crack-free specimens.•Boron-induced solute rejection during solidification leads to the formation of a fine-grained microstructure with cellular subgrains.•The microstructure of submicron α-Mo cells is surrounded by a closed network of reinforcing, intercellular Mo2B phase.•The formation of nanometer-sized boron oxide inclusions within the Mo2B phase suppresses oxide segregation and grain boundary weakening.•A bending strength of 1120 MPa at room temperature and 2265 MPa at 600 °C is achieved.</description><subject>Alloy development</subject><subject>Grain refinement</subject><subject>Laser powder-bed fusion</subject><subject>Mechanical properties</subject><subject>Microstructure</subject><subject>Molybdenum</subject><issn>0263-4368</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2023</creationdate><recordtype>article</recordtype><recordid>eNp9kM1KxDAURrNQcBx9Axd5gY5J0ybtRpDBPxhwoa5D0txoSpuUpB0Z8OHNMK5dXfi45-Peg9ANJRtKKL_tN66P49e4KUnJcsRZU52hFSk5KyrGmwt0mVJPCOEtpyv08xaGZYbCebN0YPBnVM7jCNZ5GMHPWHmDDVjoZpyWaYqQkgse5yUdYvDFGIyzLpNjGA7agF9GPCq_WNXNS8z53ik8qAQRT-HbQCx0Du1ybLlC51YNCa7_5hp9PD68b5-L3evTy_Z-V3SsLudCW2YrqwW0danrtrGsNEK0UIq60pyJqtVcGEGtsF1LVWOUqhmxFEqmO0s5W6Pq1NvFkFJ-Tk7RjSoeJCXyaE328mRNHq3Jk7WM3Z0wyLftHUSZOgc-a3Ix-5AmuP8LfgHQIn2z</recordid><startdate>202312</startdate><enddate>202312</enddate><creator>Kaserer, L.</creator><creator>Brennsteiner, D.</creator><creator>Braun, J.</creator><creator>Goettgens, V.</creator><creator>Letofsky-Papst, I.</creator><creator>Singer, P.</creator><creator>Kestler, H.</creator><creator>Schafbauer, W.</creator><creator>Leichtfried, G.</creator><general>Elsevier Ltd</general><scope>6I.</scope><scope>AAFTH</scope><scope>AAYXX</scope><scope>CITATION</scope></search><sort><creationdate>202312</creationdate><title>Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion</title><author>Kaserer, L. ; Brennsteiner, D. ; Braun, J. ; Goettgens, V. ; Letofsky-Papst, I. ; Singer, P. ; Kestler, H. ; Schafbauer, W. ; Leichtfried, G.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c352t-bf3f4fb7e952b598f32d779e2754b63749b67d71f7fc91a8daa530f1e23bcf163</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2023</creationdate><topic>Alloy development</topic><topic>Grain refinement</topic><topic>Laser powder-bed fusion</topic><topic>Mechanical properties</topic><topic>Microstructure</topic><topic>Molybdenum</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Kaserer, L.</creatorcontrib><creatorcontrib>Brennsteiner, D.</creatorcontrib><creatorcontrib>Braun, J.</creatorcontrib><creatorcontrib>Goettgens, V.</creatorcontrib><creatorcontrib>Letofsky-Papst, I.</creatorcontrib><creatorcontrib>Singer, P.</creatorcontrib><creatorcontrib>Kestler, H.</creatorcontrib><creatorcontrib>Schafbauer, W.</creatorcontrib><creatorcontrib>Leichtfried, G.</creatorcontrib><collection>ScienceDirect Open Access Titles</collection><collection>Elsevier:ScienceDirect:Open Access</collection><collection>CrossRef</collection><jtitle>International journal of refractory metals & hard materials</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Kaserer, L.</au><au>Brennsteiner, D.</au><au>Braun, J.</au><au>Goettgens, V.</au><au>Letofsky-Papst, I.</au><au>Singer, P.</au><au>Kestler, H.</au><au>Schafbauer, W.</au><au>Leichtfried, G.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion</atitle><jtitle>International journal of refractory metals & hard materials</jtitle><date>2023-12</date><risdate>2023</risdate><volume>117</volume><spage>106384</spage><pages>106384-</pages><artnum>106384</artnum><issn>0263-4368</issn><abstract>Molybdenum manufactured with laser powder bed fusion (LPBF) has an undesirable coarse-grained, columnar microstructure interspersed with intergranular cracks, high porosity, and poor mechanical strength. These defects result from a combination of the harsh LPBF process conditions and the disadvantageous properties of molybdenum, such as its high brittle-ductile transition temperature and low tolerance for oxygen impurities. In order to suppress these defect-forming mechanisms and improve the suitability for LPBF, alloy-side material adjustments with simultaneous process optimization are necessary. In this work, the effect of adjusting Mo by adding 3.5 at.% B is investigated experimentally.
Mo-3.5 at.% B specimens can be produced entirely free of cracks, with a density of 99.8%. The specimens have a microstructure of fine, equiaxed grains with an average grain size of 31 μm and an aspect ratio of 1.3, thus achieving substantial refinement of the otherwise typically coarse-grained columnar, anisotropic microstructure of pure Mo in LPBF. Furthermore, the grains possess a honeycomb-like cellular subgrain structure. This structure is formed through the solute rejection effect of B during the solidification and consists of initially solidified pure α-Mo cells with a cell size <1 μm and a honeycomb-like network of an ∼100 nm thick intercellular Mo2B phase completely covering the α-Mo cells. In addition, the formation of boron oxide inclusions, presumably B2O3, with a size of <50 nm within the Mo2B phase, provides an effective mechanism for scavenging oxygen impurities, thus ensuring segregation-free grain boundaries in Mo-3.5 at.% B.
The microstructural modifications substantially improve the mechanical properties. Under appropriate process conditions, with the substrate plate preheating temperature playing a crucial role, a bending strength of 1120 ± 172 MPa and a hardness of 379 ± 24 HV10 at room temperature can be achieved. At a test temperature of 600 °C, an increase in the bending strength to 2265 MPa is observed, and the bending angle simultaneously increases from 2° at room temperature to 35° at 600 °C. These findings indicate that the strength of Mo-3.5 at.% B is limited by the brittle behavior of the material at lower temperatures, at which residual defects are likely to initiate fracture.
[Display omitted]
•An LPBF adapted molybdenum-3.5 at.% boron alloy enables the manufacture of dense, crack-free specimens.•Boron-induced solute rejection during solidification leads to the formation of a fine-grained microstructure with cellular subgrains.•The microstructure of submicron α-Mo cells is surrounded by a closed network of reinforcing, intercellular Mo2B phase.•The formation of nanometer-sized boron oxide inclusions within the Mo2B phase suppresses oxide segregation and grain boundary weakening.•A bending strength of 1120 MPa at room temperature and 2265 MPa at 600 °C is achieved.</abstract><pub>Elsevier Ltd</pub><doi>10.1016/j.ijrmhm.2023.106384</doi><oa>free_for_read</oa></addata></record> |
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| subjects | Alloy development Grain refinement Laser powder-bed fusion Mechanical properties Microstructure Molybdenum |
| title | Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion |
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