Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser melting
In this study, a Ni50.4Ti49.6 shape memory alloy (SMA) was fabricated by selective laser melting (SLM), and it is found that heat treatments were effective to change the phase transformation behavior, microstructure, and superelasticity under compression for SLM Ni50.4Ti49.6. Detailed results based...
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2024-05-01
|
| Series: | Journal of Materials Research and Technology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S223878542400677X |
| _version_ | 1797242968931827712 |
|---|---|
| author | H.Z. Lu Z.J. Zhou Y. Yang R.C. Wang H.W. Ma W.S. Cai D.Z. Zhu C. Yang |
| author_facet | H.Z. Lu Z.J. Zhou Y. Yang R.C. Wang H.W. Ma W.S. Cai D.Z. Zhu C. Yang |
| author_sort | H.Z. Lu |
| collection | DOAJ |
| description | In this study, a Ni50.4Ti49.6 shape memory alloy (SMA) was fabricated by selective laser melting (SLM), and it is found that heat treatments were effective to change the phase transformation behavior, microstructure, and superelasticity under compression for SLM Ni50.4Ti49.6. Detailed results based on EBSD demonstrated that, for SLM Ni50.4Ti49.6 during solid solution and aging (450 °C) treatment, the ultrafine cellular and columnar grains (∼16.5 μm) in as-fabricated Ni50.4Ti49.6 became equiaxed grains (∼70.2 μm), and the frequency of low-angle grain boundaries (26.7%→13.5%) and kernel average misorientation (0.37 → 0.21) decreased. The SEM and TEM analyses show that Ti-rich Ti2Ni/Ti4Ni2Ox and Ni-rich Ni4Ti3 precipitate phases were formed in the matrix simultaneously. After solid solution treatment, the size and distribution of Ti2Ni/Ti4Ni2Ox almost unchanged with aging temperature increasing from 350 °C to 550 °C, however, the size of Ni4Ti3 in aging-treated NiTi samples increased with aging temperature obviously, and it is interesting to find that the distribution of Ni4Ti3 became uneven and dislocation networks were formed in the matrix when the aging treatment reached up to 550 °C, which originated from the internal stress generated by supersaturated Ni atoms. Furthermore, the results of superelasticity for aging-treated NiTi demonstrated that the characteristics of Ni4Ti3 precipitate phase were powerful to influence the process of superelasticity decay/fatigue instead of determining the ultimately recovery strain after 10 compressive cycles. The aging-treated NiTi with evenly-distributed, high-density, and relatively-small Ni4Ti3 precipitate phase shows minimum recovery strain at 1st cycle compression and best superelasticity stability among three aging-treated NiTi, which was attributed to strong obstruction effect of these Ni4Ti3 precipitate for the occurrence of stress-induced martensitic transformation process and formation of dislocations. In contrast, the aging-treated NiTi with unevenly-distributed and low-density Ni4Ti3 precipitate shows maximum recovery strain at 1st cycle compression and worst superelasticity stability. These results in this work can bring some meaningful insights into tailoring the microstructure and superelasticity of SLM NiTi SMAs. |
| first_indexed | 2024-04-24T18:47:39Z |
| format | Article |
| id | doaj.art-a5359ad72d2a4502bfc87e989ca39a50 |
| institution | Directory Open Access Journal |
| issn | 2238-7854 |
| language | English |
| last_indexed | 2024-04-24T18:47:39Z |
| publishDate | 2024-05-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Materials Research and Technology |
| spelling | doaj.art-a5359ad72d2a4502bfc87e989ca39a502024-03-27T04:52:16ZengElsevierJournal of Materials Research and Technology2238-78542024-05-013010441055Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser meltingH.Z. Lu0Z.J. Zhou1Y. Yang2R.C. Wang3H.W. Ma4W.S. Cai5D.Z. Zhu6C. Yang7School of Mechatronic Engineering, Guangdong Polytechnic Normal University, Guangzhou, 510665, ChinaSchool of Mechatronic Engineering, Guangdong Polytechnic Normal University, Guangzhou, 510665, ChinaSchool of Mechatronic Engineering, Guangdong Polytechnic Normal University, Guangzhou, 510665, ChinaSchool of Mechatronic Engineering, Guangdong Polytechnic Normal University, Guangzhou, 510665, ChinaNational Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou, 510640, ChinaNational Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou, 510640, ChinaNational Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou, 510640, China; Corresponding author.National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou, 510640, ChinaIn this study, a Ni50.4Ti49.6 shape memory alloy (SMA) was fabricated by selective laser melting (SLM), and it is found that heat treatments were effective to change the phase transformation behavior, microstructure, and superelasticity under compression for SLM Ni50.4Ti49.6. Detailed results based on EBSD demonstrated that, for SLM Ni50.4Ti49.6 during solid solution and aging (450 °C) treatment, the ultrafine cellular and columnar grains (∼16.5 μm) in as-fabricated Ni50.4Ti49.6 became equiaxed grains (∼70.2 μm), and the frequency of low-angle grain boundaries (26.7%→13.5%) and kernel average misorientation (0.37 → 0.21) decreased. The SEM and TEM analyses show that Ti-rich Ti2Ni/Ti4Ni2Ox and Ni-rich Ni4Ti3 precipitate phases were formed in the matrix simultaneously. After solid solution treatment, the size and distribution of Ti2Ni/Ti4Ni2Ox almost unchanged with aging temperature increasing from 350 °C to 550 °C, however, the size of Ni4Ti3 in aging-treated NiTi samples increased with aging temperature obviously, and it is interesting to find that the distribution of Ni4Ti3 became uneven and dislocation networks were formed in the matrix when the aging treatment reached up to 550 °C, which originated from the internal stress generated by supersaturated Ni atoms. Furthermore, the results of superelasticity for aging-treated NiTi demonstrated that the characteristics of Ni4Ti3 precipitate phase were powerful to influence the process of superelasticity decay/fatigue instead of determining the ultimately recovery strain after 10 compressive cycles. The aging-treated NiTi with evenly-distributed, high-density, and relatively-small Ni4Ti3 precipitate phase shows minimum recovery strain at 1st cycle compression and best superelasticity stability among three aging-treated NiTi, which was attributed to strong obstruction effect of these Ni4Ti3 precipitate for the occurrence of stress-induced martensitic transformation process and formation of dislocations. In contrast, the aging-treated NiTi with unevenly-distributed and low-density Ni4Ti3 precipitate shows maximum recovery strain at 1st cycle compression and worst superelasticity stability. These results in this work can bring some meaningful insights into tailoring the microstructure and superelasticity of SLM NiTi SMAs.http://www.sciencedirect.com/science/article/pii/S223878542400677XNiTiSelective laser meltingMicrostructural evolutionSuperelasticityHeat treatment |
| spellingShingle | H.Z. Lu Z.J. Zhou Y. Yang R.C. Wang H.W. Ma W.S. Cai D.Z. Zhu C. Yang Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser melting Journal of Materials Research and Technology NiTi Selective laser melting Microstructural evolution Superelasticity Heat treatment |
| title | Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser melting |
| title_full | Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser melting |
| title_fullStr | Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser melting |
| title_full_unstemmed | Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser melting |
| title_short | Effect of heat treatment on the microstructure and superelasticity of NiTi alloy via selective laser melting |
| title_sort | effect of heat treatment on the microstructure and superelasticity of niti alloy via selective laser melting |
| topic | NiTi Selective laser melting Microstructural evolution Superelasticity Heat treatment |
| url | http://www.sciencedirect.com/science/article/pii/S223878542400677X |
| work_keys_str_mv | AT hzlu effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting AT zjzhou effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting AT yyang effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting AT rcwang effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting AT hwma effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting AT wscai effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting AT dzzhu effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting AT cyang effectofheattreatmentonthemicrostructureandsuperelasticityofnitialloyviaselectivelasermelting |