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| 1 | Simultaneous enhancement of mechanical and shape memory properties by heat-treatment homogenization of Ti_(2)Ni precipitates in TiNi shape memory alloy fabricated by selective laser melting显示文摘The excellent shape memory and mechanical properties of Ti Ni shape memory alloys(SMAs) fabricated using selective laser melting(SLM) are highly desirable for a wide range of critical applications. In this study, we examined the simultaneous enhancement of mechanical and shape memory properties using heat-treatment homogenization of Ti_(2)Ni precipitates in a Ti_(50.6)Ni_(49.4)SMA fabricated using SLM. Specifically, because of the complete solution treatment, nanoscale spherical Ti_(2)Ni precipitates were homogeneously dispersed throughout the grain interior. Interestingly, the resultant SMA exhibited an ultrahigh tensile strength of 880 ± 13 MPa, a large elongation of 22.4 ± 0.4%, and an excellent shape memory effect, with a recovery rate of > 98% and ultrahigh recoverable strain of 5.32% after ten loading–unloading cycles. These simultaneously enhanced properties are considerably superior than those of most previously reported Ti Ni SMAs fabricated using additive manufacturing. Fundamentally, the enhancement in tensile strength is ascribed to precipitation strengthening and work hardening, and the large plasticity is mainly attributed to the homogeneous nanoscale globular Ti_(2)Ni precipitates, which effectively impeded the rapid propagation of microcracks. Furthermore, the enhanced shape memory properties are derived from the suppression of dislocation movement and formation of retained stabilized martensite by the presence of high-density dislocations, nanoscale Ti_(2)Ni precipitates, and abundant interfaces. The obtained results provide insight into the enhancement of the two types of properties in Ti Ni SMAs and will accelerate the wider application of SMAs. | H.Z.Lu L.H.Liu C.Yang X.Luo C.H.Song Z.Wang J.Wang Y.D.Su Y.F.Ding L.C.Zhang Y.Y.Li | 2022 | Journal of Materials Science & Technology2022，，6： | 5 |
| 2 | Overcoming the strength-ductility trade-off by tailoring grain-boundary metastable Si-containing phase in β-type titanium alloy显示文摘It is well accepted that grain-boundary phases in metallic alloys greatly deteriorate the mechanical properties.In our work,we report on a novel strategy to prepare high strength-ductility β-type(Ti69.71 Nb23.72Zr4.83Ta1.74)97Si3(at.%)(TNZTS) alloys by tailoring grain-boundary metastable Si-containing phase.Specifically,the thin shell-shaped metastable S1 phase surrounding the columnar β-Ti grain was intercepted successfully via nonequilibrium rapid solidification achieved by selective laser melting(SLM).Subsequently,the thin shell-shaped metastable(Ti,Nb,Zr)5 Si3(called S1) phase was transformed into globular(Ti,Nb,Zr)2 Si(called S2) phase by the solution heat treatment.Interestingly,the globular S2 phases reinforced TNZTS alloy exhibits ultrahigh yield strength of 978 MPa,ultimate strength of 1010 MPa and large elongation of 10.4 %,overcoming the strength-ductility trade-off of TNZTS alloys by various methods.Especially,the reported yield strength herein is 55 % higher than that of conventionally forged TNZT alloys.Dynamic analysis indicates the globularization process of the metastable S1 phase is controlled by the model of termination migration.The quantitative analysis on strengthening mechanism demonstrates that the increase in yield strength of the heat-treated alloys is mainly ascribed to the strengthening of the precipitated silicide and the dislocations induced by high cooling rate.The obtained results provide some basis guidelines for designing and fabricating β-titanium alloys with excellent mechanical properties,and pave the way for biomedical application of TNZTS alloy by SLM. | X.Luo L.H.Liu C.Yang H.Z Lu H.W.Ma Z.Wang D.D.Li L.C.Zhang Y.Y.Li | 2021 | Journal of Materials Science & Technology2021，，9： | 5 |
| 3 | Comparison of microstructure and mechanical behavior of Ti-35Nb manufactured by laser powder bed fusion from elemental powder mixture and prealloyed powder显示文摘Although different types of powder feedstock are used for additive manufacturing via laser powder bed fusion(L-PBF),limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those powder feedstock.This work investigated the microstructure,phase composition,melt pool morphology,and mechanical properties of a prealloyed Ti-35Nb alloy manufactured using L-PBF and compared these to their counterparts produced from elemental powder mixture.The samples manufactured from the powder mixture are composed of randomly distributed undissolved Nb in theα/βmatrix,resulting from the unstable melt pool during the melting of the powder mixture.By contrast,parts produced from prealloyed powder display a homogeneous microstructure withβandαphases,owing to the full melting of prealloyed powder,therefore,a more stable melt pool to achieve a homogeneous microstructure.The Ti-35Nb manufactured from prealloyed powder exhibits large tensile ductility(about 10 times that of the counterparts using mixed powder),attributed to the high homogeneity in microstructure and chemical composition,strong interface bonding,relatively low oxygen content,and the existence of a large amount ofβphase.This work sheds insights into understanding the effect of powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts. | J.C.Wang Y.J.Liu S.X.Liang Y.S.Zhang L.Q.Wang T.B.Sercombe L.C.Zhang | 2022 | Journal of Materials Science & Technology2022，，10： | 4 |
| 4 | Strong enhancement on dye photocatalytic degradation by ball-milled TiO2:A study of cationic and anionic dyes显示文摘TiO_2 particles with desirable properties were produced by undergoing specific durations of ball milling.Characterizations of the TiO_2 particles before and after ball milling were investigated via X-ray diffraction(XRD), Brunauer-Emmett-Teller(BET), particle size analysis, zeta potential, and scanning electron microscope(SEM). The equilibrium adsorption data were well fitted to Langmuir, Freundlich, and Dubinin-Radushkevich(D-R) isotherms. Compared to the as-received TiO_2(mean particle size d150= 0.78μm, specific surface area = 88.17 m^2g^(-1), pore volume = 0.41 cm^3g^(-1)), the 60 min ballmilled TiO_2(d50= 0.55 μm, specific surface area = 99.48 m2g^(-1), pore volume = 0.48 cm3g^(-1)) enhanced the adsorption quantity of congo red and methylene blue from 10.4 mg g^(-1)to 13.6 mg g^(-1), and from17.0 mg g^(-1)to 22.2 mg g^(-1), respectively; and also improved the kinetic rates from k = 0.1325 to 0.2193, and k = 0.0944 to 0.1553, respectively. Dye adsorption and degradation efficiency of congo red was enhanced in acidic p H range(2–5.14), and methylene blue was enhanced in alkaline p H range(7.58–12). | Z.Jia L.B.T.La W.C.Zhang S.X.Liang B.Jiang S.K.Xie D.Habibi L.C.Zhang | 2017 | Journal of Materials Science & Technology2017，33，8： | 4 |
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