Microstructure and Properties of As-Cast Co-28Cr Alloy with Aging Treatment AITranslate

［1］（孟钰权，常慧，白天祥，李志强. CoCrNiAl0.1Si0.1中熵合金动态力学响应及其变形机制研究［J］.稀有金属，2023，47（7）：942.）

Y Q Meng，H Chang，T X Bai，Z Q Li. Dynamic mechanical responses and deformation mechanism of CoCrNiAl0.1Si0.1 medium-entropy alloy［J］.Chinese Journal of Rare Metals，2023，47（7）：942.

［2］（赵雪柔，吕煜坤，武上焜，李双元. Mo对铸态（Fe50Mn30Co10Cr10）98-xC2Mox多主元合金组织及性能的影响［J］.塑性工程学报，2024，31（5）：163.）

X R Zhao，Y K Lu，S K Wu，S Y Li. Effect of Mo on microstructure and properties of as-cast （Fe50Mn30Co10Cr10）98-xC2Mox multi-principal element alloys［J］.Journal of Plasticity Engineering，2024，31（5）：163.

［3］（薛润东，王成猛，万润. 热成形工艺对GH5188钴基高温合金薄板晶界特征分布的影响［J］.锻压技术，2024，49（4）：68.）

R D Xue，C M Wang，R Wan. Effects of hot forming process on grain boundary characteristic distribution of cobalt-base superalloy GH5188 sheet［J］.Forging & Stamping Technology，2024，49（4）：68.

［4］（赵卓，刘玉杰，马廷威，程利凯，高敏坤. 关键元素对Co-30Ni-4Al-3W合金组织性能影响的热力学解析［J］.有色金属工程，2022，12（12）：36.）

Z Zhao，Y J Liu，T W Ma，L K Cheng，M K Gao. Thermodynamic analysis of the effect of key elements on the microstructure and properties of Co-30Ni-4Al-3W alloy［J］.Nonferrous Metals Engineering，2022，12（12）：6.

［5］（郭珲，赵刘会. 有色金属基纳米材料及复合材料的研究进展［J］.铜业工程，2023，（2）：74.）

H Guo，L H Zhao. Research progress of non-ferrous metal-based nanomaterials and composites［J］.Copper Engineering，2023，（2）：74.

［6］（刘含笑，刘凯，王祥德，薛婷婷，郭飞，吕东芹，王巍. 电位滴定法测定铁中间合金中铁含量［J］.分析试验室，2024，43（6）：858.）

H X Liu，K Liu，X D Wang，T T Xue，F Guo，D Q Lv，W Wang. Determination of iron content in intermediate ferroalloy by automatic potentiometric titration method［J］.Chinese Journal of Analysis Laboratory，2024，43（6）：858.

［7］Girão D D C，Béreš M，Jardini A L，Filho R M，Silva C C，Siervo A D，Abreu H F G D，Araújo W S. An assessment of biomedical CoCrMo alloy fabricated by direct metal laser sintering technique for implant applications［J］.Materials Science and Engineering：C，2020，107：110305.

［8］（徐晓卫，董鑫，李宁，张幖，张玉鲜. SLM成形生物医用钴铬合金的研究现状［J］.金属加工（热加工），2022，（10）：7.）

X W Xu，X Dong，N Li，B Zhang，Y X Zhang. The recent research of biomedical Co-Cr alloy fabricated by selective laser melting［J］.MW Metal Forming，2022，（10）：7.

［9］Kurosu S，Matsumoto H，Chiba A. Isothermal phase transformation in biomedical Co-29Cr-6Mo alloy without addition of carbon or nitrogen［J］.Metallurgical and Materials Transactions A，2010，41（10）：2613.

［10］Kajima Y，Takaichi A，Kittikundecha N，Nakamoto T，Kimura T，Nomura N，Kawasaki A，Hanawa T，Takahashi H，Wakabayashi N. Effect of heat-treatment temperature on microstructures and mechanical properties of Co-Cr-Mo alloys fabricated by selective laser melting［J］.Materials Science & Engineering A，2018，726：21.

［11］Aaronson H I. Mechanisms of the massive transformation［J］.Metallurgical and Materials Transactions A，2002，33（8）：2285.

［12］Dahn N C，Morphy D，Rajan K. Kinetics of the martensitic fcc→hcp transformation in Co-Cr-Mo alloy powders［J］.Acta Metallurgica，1984，32（9）：1317.

［13］Kurosu S，Matsumoto H，Chiba A. Isothermal phase transformation in biomedical Co-29Cr-6Mo alloy without addition of carbon or nitrogen［J］.Metallurgical and Materials Transactions A，2010，41：2613.

［14］Sande J B V，Coke J R，Wulff J. A transmission electron microscopy study of the mechanisms of strengthening in heat-treated Co-Cr-Mo-C alloys［J］.Metallurgical Transactions A，1976，7：389.

［15］Rajan K. Phase transformations in a wrought Co-Cr-Mo-C alloy［J］.Metallurgical Transactions A，1982，13：1161.

［16］Zhou Y A，Li N，Yan J Z，Zeng Q. Comparative analysis of the microstructures and mechanical properties of Co-Cr dental alloys fabricated by different methods［J］.The Journal of Prosthetic Dentistry，2018，120（4）：617.

［17］Wei W，Zhou Y A，Liu W B，Li N，Yan J Z，Li H P. Microstructural characterization，mechanical properties，and corrosion resistance of dental Co-Cr-Mo-W alloys manufactured by selective laser melting［J］.Journal of Materials Engineering and Performance，2018，27：5312.

［18］Ko K H，Kang H G，Huh Y H，Park C J，Cho L R. Effects of heat treatment on the microstructure，residual stress，and mechanical properties of Co-Cr alloy fabricated by selective laser melting［J］.Journal of the Mechanical Behavior of Biomedical Materials，2022，126：105051.

［19］Yildirim M，Keles A. Effect of aging time on phase transformation，microstructure and hardness of Co-Cr-Mo alloys［J］.Selcuk University Journal of Engineering Science and Technology，2019，7（1）：146.

［20］Shan L，Wang Y X，Li J L，Li H，Wu X D，Chen J M. Tribological behaviours of PVD TiN and TiCN coatings in artificial seawater［J］.Surface & Coatings Technology，2013，226：40.

［21］Li Z M，Tasan C C，Pradeep K G，Raabe D. A trip-assisted dual-phase high-entropy alloy：grain size and phase fraction effects on deformation behavior［J］.Acta Materialia，2017，7：323.

［22］Mani A，Salinas R，López H F. Deformation induced fcc to hcp transformation in a Co-27Cr-5Mo-0.05C alloy［J］.Materials Science and Engineering：A，2011，528（7−8）：3037.

［23］Koizumi Y，Suzuki S，Yamanaka K，Lee B S，Sato K，Li Y P，Kurosu S，Matsumoto H，Chiba A. Strain-induced martensitic transformation near twin boundaries in a biomedical Co-Cr-Mo alloy with negative stacking fault energy［J］.Acta Mater，2013，61（5）：1648.

［24］Yamanaka K，Mori M，Chiba A. Enhanced mechanical properties of as-forged Co-Cr-Mo-N alloys with ultrafine-grained structures［J］.Metallurgical and Materials Transactions A，2012，43：5243.

［25］Yamanaka K，Mori M，Chiba A. Effects of nitrogen addition on microstructure and mechanical behavior of biomedical Co-Cr-Mo alloys［J］.Journal of the Mechanical Behavior of Biomedical Materials，2014，29：417.

［26］Luo H W，Wang X H，Liu Z B，Yang Z Y. Influence of refined hierarchical martensitic microstructures on yield strength and impact toughness of ultra-high strength stainless steel［J］.Journal of Materials Science & Technology，2020，51：130.

［27］Takaichi A，Suyalatu，Nakamoto T，Joko N，Nomura N，Tsutsumi Y，Migita S，Doi H，Kurosu S，Chiba A，Wakabayashi N，Igarashi Y，Hanawa T. Microstructures and mechanical properties of Co-29Cr-6Mo alloy fabricated by selective laser melting process for dental applications［J］.Journal of the Mechanical Behavior of Biomedical Materials，2013，21：67.

［28］Hauser M，Wendler M，Weiß A，Volkova O，Mola J. On the critical driving force for deformation-induced α′-martensite formation in austenitic Cr-Mn-Ni Steels［J］.Advanced Engineering Materials，2019，21（5）：1800676.

［29］Tonizzo Q，Mazière M，Perlade A，Gourgues-Lorenzon A F. Effect of austenite stability on the fracture micromechanisms and ductile-to-brittle transition in a medium-Mn，ultra-fine-grained steel for automotive applications［J］.Journal of Materials Science，2020，55（22）：9245.

Basic Information:

DOI：10.13373/j.cnki.cjrm.XY23090008

Chinese Library Classification Number:TG156

Citation Information:

Co-28Cr alloy has the prospect of application in the jewelry field due to its high strength，wear resistance，corrosion resistance，and biocompatibility，and has similar luster appearance to gold，silver，and platinum precious metal. The ring cast with Co-28Cr alloy are often broken at the ring grip，due to its high volume fraction of the hcp phase，which make the alloy have a high microhardness，strength，and insufficient toughness. In this work，the as-cast Co-28Cr alloy was selected as the research object. In order to obtain high toughness，the fcc stable elements Mn，Ti，Fe，and C were added to make the alloy have a high volume fraction of the fcc phase. The solution treatment process of 1250 ℃/4 h water cooling （WC） and the aging treatment process of 600~700 ℃/1 h WC were adopted. The microstructure of the tensile surface of the alloy after different aging treatment and three-point bending was observed by AxioVert. A1 optical microscope （OM）. The phase and strain distributions of the samples with different aging treatments were analyzed by SYMMETRY electron backscatter diffractometer （EBSD）. The effects of aging temperature on microstructure，mechanical properties and fracture morphology of as-cast Co-28Cr alloy were studied by room temperature three point bending test and microhardness test with WDW-50 universal testing machine and HV-1000 digital hardness tester. The results showed that the microstructure of the as-cast Co-28Cr alloy consisted of fcc phase，hcp phase，and a small amount of Cr₂₃C₆ and TiN. After solid solution treatment，there was basically no dendritic structures in Co-28Cr alloy，and Cr₂₃C₆ changed from strip to sphere. During aging treatment at 600 or 650 ℃，the isothermal martensite was formed on the stacking fault and the athermal martensite of thick was formed on the grain boundary. It could be seen from the EBSD micrographs that the volume fraction of hcp phase increased gradually from 13% to 26% with the increase of aging temperature. The volume fraction of hcp phase in 700 ℃/1 h WC sample was twice as much as that in 600 C/1 h WC sample. When the aging temperature was 600 or 700 ℃，the width of hcp phase laths was fine and the quantity was large. When the aging temperature was 650 ℃，the width of hcp phase laths was thicker and the quantity was less. In the process of martensite transformation，isothermal martensite required greater driving force and internal strain than that of athermal martensite，therefore，the local average misorientation （LAM） value of isothermal martensite was higher than that of athermal martensite. With the increase of aging temperature，the microhardness and bending strength of the alloy increased，because with the increase of the volume fraction of hcp phase，the strength of the alloy increased. When the aging temperature was 650 ℃，the bending angle of the alloy was the largest，mainly due to the finer the laths of hcp phase and strong bending resistance. After the three-point bending test，strain-induced martensite transformation （SIMT） from fcc phase to hcp phase occurred，which was the main deformation mechanism. When the aging temperature was 650 ℃，the angle between the strain-induced martensite laths was 90° and the average width of laths was 16.5 μm，therefore，the bending property of the alloy was better. When the aging temperature was 600 or 700 ℃，the angle of strain-induced martensite laths were smaller and the average width of laths were finer，the bending property of the alloy was worse. The results showed that the best matching heat treatment system for strength and toughness of as-cast Co-28Cr alloy for ring was （1250 ℃/4 h WC）+（650 ℃/1 h WC）.