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Ni 25 Ti 25 Hf 25 Cu 25 medium entropy shape memory alloy (MESMA) exhibit reversible B2↔B19′ martensitic transformation. Martensitic morphology is represented by (011) type I twins with low density of inner (001) compound twins. In a bending test, Ni 25 Ti 25 Hf 25 Cu 25 exhibits reversible strain of 2.4% under stress of 300 MPa. [Display omitted] • Ni 25 Ti 25 Hf 25 Cu 25 exhibits B2↔B19′ MT. • Low density of (001) compound twins into martensitic variants. • Recoverable strain of 2.4% under stress of 300 MPa. [ABSTRACT FROM AUTHOR]

Decarburization means carbon in rail material lost in the hot rolled process. It changes the microstructure of rail materials and will influence their rolling contact fatigue (RCF) characteristic. The objective of this study is to explore the effect of decarburized layer on rolling contact fatigue and propagation mechanism of crack under the wet condition using a rolling-sliding wear testing machine. The results show that the crack growth rate on the decarburized rail roller is over 4 times than that on the non-decarburized rail. Small pitting presents on the non-decarburized rail roller, which is dominated by transgranular crack. While, long mouth surface crack dominates on the decarburized rail roller and the cracks mainly grow along the ferrite line or the grain boundary. With the cycles increasing, the surface cracks of decarburized rail roller gradually break and forms spalling damage, eventually expands to bulk spalling. Meanwhile, the crack growth mechanism changes back to the transgranular propagation and propagates in depth with a large angle when the decarburization is worn off. [ABSTRACT FROM AUTHOR]

• Effects of the initial microstructure of the railway wheel steel on adiabatic shearing behavior is examined. • The localized deformation of proeutectoid ferrite is preferent to that of pearlite. • The localized deformation is more serious in the wide lamellar structure than in the narrow lamellar structure. • The rim is more prone to adiabatic shearing compared with the web. Adiabatic shearing behavior in the web and the rim of high-speed train railway wheel steel was investigated using a split Hopkinson pressure bar (SHPB) with hat-shaped punch shear technique. Different initial microstructure characteristics were observed in the web and the rim specimens experiencing different heat treatment. For the first time we show that the pre-eutectoid ferrite deforms at first and pearlite interlamellar spacing has a significant influence on structural softening sequence during shear band evolution in the railway wheel steel, and shear bands are more prone to emerge in the rim. [ABSTRACT FROM AUTHOR]

The microstructure and corrosion fatigue behavior under artificial seawater environment of 100-mm-thick Ti–6Al–4V alloy joint via vacuum electron beam welding (EBW) was systematically characterized. Obvious microstructural heterogeneity along the transverse direction of as-welded joint was observed. Bimodal-phases microstructure of granular α colonies and β strips compose the microstructure of the base metal (BM). While the microstructure of fusion zone (FZ) comprises single-phase acicular α/α′ martensite. Under corrosive environment of artificial seawater, FZ shows a lower growth rate of corrosion fatigue cracking (CFC) than that in the BM. Increasing content of residual gas contamination worsens the resistance against corrosion fatigue of the FZ of Ti–6Al–4V alloy joint. Results of local electrochemical characterization indicates that the FZ shows a better resistance against electrochemical corrosion than that of the BM. It is deduced that the slower growth rate of CFC observed in the FZ originates from the combined effects of the excellent corrosion resistance of martensite microstructure and the obstructions of interfaces of fine α/α′ laths against growth of CFC. Moreover, the growth mechanisms of CFC in the BM and FZ were discussed involving the microstructural heterogeneity of the EBW joint. Image 1 • Elucidating the correlation between the microstructure and corrosion fatigue behavior of thick Ti–6Al–4V EBW joint. • Microstructure heterogeneity between base metal (BM) and fusion zone (FZ) affects obviously the corrosion fatigue behavior. • Subtle change of welding vacuum shows significant influence on the welding quality. • Growth rate of corrosion fatigue cracking (CFC) in BM is higher than that in FZ. • CFC prefers to traverse β phase grains in BM, while penetrates the acicular α/α′ lath in FZ. [ABSTRACT FROM AUTHOR]