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Sunghak Lee - One of the best experts on this subject based on the ideXlab platform.
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Effects of Mo Addition on crack tip opening displacement (CTOD) in heat affected zones (HAZs) of high-strength low-alloy (HSLA) steels
Scientific reports, 2019Co-Authors: Seok Gyu Lee, Bohee Kim, Woo Gyeom Kim, Sunghak LeeAbstract:Effects of Mo Addition on microstructures and crack tip opening displacement (CTOD) in heat affected zones (HAZs) of three high-strength low-alloy (HSLA) steels were investigated in this study, and the correlation between them was explained by fracture mechanisms related with martensite-austenite constituent (MA) characteristics. The coarse-grained HAZ (CGHAZ) consisted of acicular ferrite (AF), granular bainite (GB), and bainitic ferrite (BF), whereas the inter-critically heated HAZ (ICHAZ) consisted of quasi-polygonal ferrite (QPF), GB, and MA. Since Mo proMoted the formation of GB, BF, and MA and prevented the formation of AF and QPF, the CTOD decreased in both HAZs with increasing Mo content. According to the interrupted three-point bending test results of the ICHAZ where many MAs were distributed in the QPF or GB matrix, many voids were observed mainly at MA/QPF interfaces, which implied that the void initiation at the interfaces was a major fracture mechanism. The atomic probe data of MAs indicated the segregation of C, Mn, Mo, and P at MA/QPF interfaces, which could result in the easy MA/matrix interfacial debonding to initiate voids. Thus, characteristics of MA/QPF interfaces might affect More importantly the CTOD than the MA volume fraction or size.
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effects of mn and Mo Addition on high temperature tensile properties in high ni containing austenitic cast steels used for turbo charger application
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: Seungmun Jung, Changwoo Jeon, Wonmi Choi, Byeongjoo Lee, Giyong Kim, Seongsik Jang, Sunghak LeeAbstract:Abstract Since turbo-chargers require More excellent high-temperature properties to maintain their structures at further higher exhaust gas temperatures up to 1050 °C, a 20 wt%-Ni-containing austenitic cast steel (N20 steel) has been suggested as a promising candidate cast steel. However, this steel is very expensive because it contains a large aMount of expensive Ni. In order to partly replace expensive Ni by inexpensive Mn and to improve high-temperature tensile properties in the N20 steel, three austenitic cast steels were fabricated by replacing 6 wt% of Ni by 6.9 wt% of Mn or by adding 2–4 wt% of Mo. TherModynamically calculated fractions of equilibrium phases (austenite, ferrite, and M 7 C 3 carbide) were matched with experimentally measured fractions, although they were somewhat overestimated. The N14 steel where 6 wt% Ni was replaced by 6.9 wt% of Mn did not contain any ferrite, and showed comparable or More excellent high-temperature tensile properties than those of the N20 steel, which indicated the successful replacement up to 6 wt% Ni by Mn, together with alloying cost reduction of 10%. The Mo Addition also favorably affected high-temperature properties because Mo worked for increasing both M 7 C 3 fraction and austenite matrix hardness. Simultaneously considering mechanical properties and alloying costs, therefore, these Mo-containing N14 steels can be fully adopted for high-performance turbo-chargers requiring excellent high-temperature properties.
Qiang Feng - One of the best experts on this subject based on the ideXlab platform.
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influence of Mo and ru Additions on the creep behavior of ni based single crystal superalloys at 1100 c
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Jiajie Huo, Yunrong Zheng, Qianying Shi, Qiang FengAbstract:Abstract In order to obtain More knowledge to replace or lower the content of expensive and heavy elements Re and Ru in advanced Ni-based single crystal superalloys, the role of Ru playing in the microstructure and creep performance at 1100 °C and 140 MPa was evaluated in this study by considering its individual effect and also synergizing it with Mo to maximize the beneficial effect from each element. A series of single crystal superalloys with varying alloying elements were investigated and their initial microstructure and microstructural evolution during the creep deformation were characterized. It was shown that both Mo and Ru could increase the γ/γ' lattice misfit and density of interfacial dislocations, that contributed to improve the creep resistance at high temperature and low stress condition. The inferior microstructural stability regarding to the TCP phase formation in alloys with More Mo Addition lowered creep performance to some extent, however, that could be restrained by the Addition of Ru. The high temperature and low stress creep performance could be enhanced by the co-Addition of Mo and Ru since their synergistic effect could be able to enhance the γ/γ' interfacial strengthening and retain the microstructural stability.
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effect of Mo Addition on as cast microstructures and properties of grey cast irons
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Xianfei Ding, Hong Huang, Warkentin Matthias, Shiyao Huang, Qiang FengAbstract:Abstract High performance cast iron (HPCI) with improved mechanical properties and tuned thermal conductivity is a strong candidate to replace ductile iron in the application of autoMobile components. Effect of Mo on as-cast microstructures and properties of the grey cast iron was investigated to clarify the roles of Mo element and possibility of developing HPCI through Mo Addition. The results show that Mo Addition leads to Mo micro-segregation as well as Mo2P and carbides precipitation in the grey cast irons. Mo Addition can produce the chemical inhoMogeneity and thus uneven graphite flake distribution in the alloys. The thermal expansion coefficient can be reduced by Mo Addition. Lower Mo Addition refines the majority of graphite flakes but increases the length of a small fraction of graphite flakes and consequently improves the thermal conductivity, while higher Mo Addition induces to precipitation and solution strengthening thus enhances the UTS. Therefore, Moderate Mo Addition is an effective way to develop HPCI.
Grant X Chen - One of the best experts on this subject based on the ideXlab platform.
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enhanced elevated temperature properties via Mo Addition in al mn mg 3004 alloy
Journal of Alloys and Compounds, 2017Co-Authors: Kun Liu, Grant X ChenAbstract:Abstract The present work investigates the influence of adding Mo to an Al-Mn-Mg 3004 alloy on elevated-temperature properties as well as their thermal stability during long-term thermal holding at 350 °C and 400 °C. In as-cast and heat-treated conditions, both microhardness and yield strength increase with increasing Mo contents and reach peak values at 0.3 wt. % followed by a plateau. With an optimized Mo content (0.3 wt. %), the volume fraction of dispersoids is increased while the volume percentage of the dispersoid-free zone is greatly reduced compared to the base alloy free of Mo, resulting in the remarkable increases in elevated-temperature strength and creep resistance. The results of the long-term thermal holding show that compared with the rapid drop of elevated-temperature strength and creep resistance in the base alloy, the Al-Mn-Mg alloy with 0.3% Mo is thermally stable up to 350 °C, exhibiting a slight decrease of stability at 400 °C. The combination of high elevated-temperature properties and their excellent thermal stability at 350–400 °C with Mo Addition makes Al-Mn-Mg 3xxx alloys the promising candidates for elevated-temperature applications.
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dispersoid strengthening of a high temperature al si cu mg alloy via Mo Addition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: A R Farkoosh, Grant X Chen, Mihriban PekguleryuzAbstract:Abstract The influence of Mo Addition on the microstructure and mechanical properties of an Al–7Si–0.5Cu–0.3Mg alloy (wt%) was investigated. The Mo-containing alloy exhibited significant improvement in creep resistance over the base alloy. At 300 °C and 30 MPa, the minimum creep rate decreased by 95% while creep time-to-fracture was increased by 2 orders of magnitude, from 50 min to 1500 min. The tensile yield strength at 300 °C was also increased by 25%. These effects were attributed to the formation of novel Al–(Fe,Mo)–Si dispersoids during solution treatment in the grain interiors (intradendritic regions). Unlike the age-hardening precipitates, which coarsened resulting in loss of strength, these dispersoids were thermally stable and retained their strengthening effect at 300 °C. TEM investigations showed that the dislocation Motions were effectively hindered by these fine dispersoids, leading to the reduction in the minimum creep rate. The onset of the tertiary creep stage was delayed by postponing the dislocation pile-up at the interdendritic Si particles. It was found that Mo Addition suppressed the formation of the brittle plate-like β-Al5FeSi intermetallics and formed a blocky phase in the cast microstructure, which resulted in 34% increase in elongation at 300 °C.
Hiroyuki Y Yasuda - One of the best experts on this subject based on the ideXlab platform.
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improvement of room and high temperature tensile properties of nial strengthened ferritic heat resistant steels through Mo Addition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Ken Cho, Kenshi Ikeda, Hiroyuki Y YasudaAbstract:Abstract In order to improve the room and high temperature strength–ductility balance of ferritic Fe-Al-Ni based alloys strengthened by the B2-type NiAl precipitates, Fe-Al-Ni-Cr-Mo alloys was developed. The microstructures and tensile properties of the alloys were examined focusing on Mo content. We found that the 2 at% or 4 at% Mo Addition is effective in the improvement of the elongation of the Fe-Al-Ni based alloys at room temperature (RT) while maintaining high strength, which reflects the suppression of intergranular fracture by the strengthening of the bcc matrix by Mo Addition. We also found that the RT tensile properties and deformation behavior of the alloys depend strongly on the volume fraction and the size of the NiAl precipitates. For instance, the yield stress decreases by the change in the primary slip direction from to and the formation of the Orowan loops with increasing the volume fraction and the mean diameter of the NiAl precipitates. In Addition, the alloy with the appropriate Mo content exhibits a high yield stress above 660 MPa up to 923 K, owing to the solid-solution hardening by Mo Addition and the low growth rate of the NiAl precipitates even at high temperatures. These findings indicate that the alloys have a great potential for steam turbines of advanced ultra‐supercritical thermal power plants.
Ken Cho - One of the best experts on this subject based on the ideXlab platform.
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improvement of room and high temperature tensile properties of nial strengthened ferritic heat resistant steels through Mo Addition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Ken Cho, Kenshi Ikeda, Hiroyuki Y YasudaAbstract:Abstract In order to improve the room and high temperature strength–ductility balance of ferritic Fe-Al-Ni based alloys strengthened by the B2-type NiAl precipitates, Fe-Al-Ni-Cr-Mo alloys was developed. The microstructures and tensile properties of the alloys were examined focusing on Mo content. We found that the 2 at% or 4 at% Mo Addition is effective in the improvement of the elongation of the Fe-Al-Ni based alloys at room temperature (RT) while maintaining high strength, which reflects the suppression of intergranular fracture by the strengthening of the bcc matrix by Mo Addition. We also found that the RT tensile properties and deformation behavior of the alloys depend strongly on the volume fraction and the size of the NiAl precipitates. For instance, the yield stress decreases by the change in the primary slip direction from to and the formation of the Orowan loops with increasing the volume fraction and the mean diameter of the NiAl precipitates. In Addition, the alloy with the appropriate Mo content exhibits a high yield stress above 660 MPa up to 923 K, owing to the solid-solution hardening by Mo Addition and the low growth rate of the NiAl precipitates even at high temperatures. These findings indicate that the alloys have a great potential for steam turbines of advanced ultra‐supercritical thermal power plants.
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improvement of microstructure mechanical and corrosion properties of biomedical ti mn alloys by Mo Addition
Materials & Design, 2016Co-Authors: Pedro Fernandes Santos, Ken Cho, Mitsuo Niinomi, Huihong Liu, Masaaki Nakai, Adhitya Trenggono, Sebastien Champagne, Hendra Hermawan, Takayuki NarushimaAbstract:Abstract In previous studies, Ti-Mn alloys showed promising performance for biomedical applications, but their elongation required improvement. In this study, Mo was added to Ti-Mn alloys to proMote mechanical twinning and improve their ductility. Four alloys for biomedical applications were designed and fabricated by cold crucible levitation melting: Ti-5Mn-3Mo (TMM-53), Ti-5Mn-4Mo (TMM-54), Ti-6Mn-3Mo (TMM-63), and Ti-6Mn-4Mo (TMM-64). The microstructure, mechanical properties, tensile deformation mechanisms, and electrochemical corrosion properties of the alloys were evaluated. Their hardness ranges from 336 to 373 HV. Their Young's Modulus ranges from 89 to 100 GPa. Both hardness and Young's Modulus tend to decrease with decreasing aMount of athermal ω phase, which is caused by increasing alloying elements contents. Mo Addition improves the elongation of TMM-53 and TMM-54 by proMoting twinning. Conversely, it increases the tensile strength of TMM-63 and TMM-64. Particularly, TMM-54 shows an elongation of 34% with an ultimate tensile strength (UTS) of 935 MPa. TMM-63 shows an elongation of 14% and a UTS of 1220 MPa, associated to the formation of deformation-induced ω phase. Moreover, Mo Addition decreases the corrosion rate of the Ti-Mn alloys to a level comparable to that of commercially-pure Ti.