A nanoindentation strain-rate jump technique has been developed for determining the local strain-rate sensitivity (SRS) of nanocrystalline and ultrafine-grained (UFG) materials. The results of the new method are compared to conventional constant strain-rate nanoindentation experiments, macroscopic compression tests, and finite element modeling (FEM) simulations. The FEM simulations showed that nanoindentation tests should yield a similar SRS as uniaxial testing and generally a good agreement is found between nanoindentation strain-rate jump experiments and compression tests. However, a higher SRS is found in constant indentation strain-rate tests, which could be caused by the long indentation times required for tests at low indentation strain rates. The nanoindentation strain-rate jump technique thus offers the possibility to use single indentations for determining the SRS at low strain rates with strongly reduced testing times. For UFG-Al, extremely fine-grained regions around a bond layer exhibit a substantial higher SRS than bulk material.

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Nanoindentation strain-rate jump tests for determining the local strain-rate sensitivity in nanocrystalline Ni and ultrafine-grained Al

The oxidation processes of Fe(II) hydroxo-complexes to α-, β-, γ-, and δ-FeOOH and Fe3O4, which are important atmospheric products of steels, and the effect of Cu2+, PO43− ion on the oxidation of the Fe(II) hydroxo-complexes in aqueous solutions have been investigated. The mechanism of atmospheric rusting deduced from the results obtained in the present investigation has been used to explain the difference in behaviour between ordinary mild steels and low alloy steels during atmospheric exposure. It is concluded that Fe(II) complexes are transformed to amorphous δ-FeOOH by the catalytic effect of Cu and P present in steels. The amorphous δ-FeOOH forms a compact rust layer that enhances corrosion resistance of the steel.

The Mechanism of Atmospheric Rusting and the Effect of Cu and P on the Rust Formation of Low Alloy Steels

https://digital.csic.es/bitstream/10261/94988/1/Wheathering%20steels.pdf

Weathering steels: From empirical development to scientific design. A review

This article is a literature review of recent advances in novel Fe-Mn based alloys, drawing specific examples on Hadfield and TWIP steels, and high entropy and shape memory alloys. A critical discussion of these alloys merits a uniform treatment owing to their remarkable mechanical attributes, i.e. a substantial combination of strength and ductility. It is interesting to note that their microscopic deformation mechanism also shares commonality in terms of twinning-dominated straining in addition to slip-based plasticity. In the past two decades alone, a synergy of materials science and mechanics based studies has significantly helped uncover the microstructural origin, effects of alloying etc. therein. In this paper, we discourse elaborately on the reported microstructure-property correlations. By surveying these developments, we point out how the current knowledgebase can pave the way for strategizing future materials advancements as well as expanding applications.

On deformation behavior of Fe-Mn based structural alloys

Post-deposition annealing effects on nanomechanical properties of granular TiO2 films on soda-lime glass substrates were studied. In particular, the effects of Na diffusion on the films’ mechanical properties were examined. TiO2 photocatalyst films, 330 nm thick, were prepared by dip-coating using a TiO2 sol, and were annealed between 100 °C and 500 °C. Film’s morphology, physical and nanomechanical properties were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, differential thermo-gravimetric analysis, and nanoindentation. Contrary to expectations, the maximum film hardness was achieved for 300°C annealing, with a value of 0.69 ± 0.05 GPa. Higher annealing temperatures resulted in inferior mechanical properties. No pile-up or sink-in effects were observed with minimal creep for the 300 °C annealed sample. Considerable decrease in the amount of chemisorbed water was found with increasing annealing temperature, causing gel films densification, explaining the i...

/pdf/nanomechanical-properties-of-tio2-granular-thin-films-1tk9k0o5sl.pdf

Nanomechanical properties of TiO2 granular thin films.

Characterization of the solidification structure and texture development of ferritic stainless steel produced by twin-roll strip casting

Evolution of cube texture in strip-cast non-oriented silicon steels

This paper reports the mechanical properties of Ni films fabricated by pulse electrodeposition. Transmission electron microscope revealed that the prepared films had an average grain size of 25 nm with a narrow size distribution and the absence of dislocations. Small grain size leads to an increasing hardness as high as 7.8 GPa while Young's moduli keep a constant bulk value of 215 GPa, resulting in an increasing ratio of hardness ( H ) to elastic modulus ( E ). Interestingly, the wear resistance was also improved significantly. Under a constant normal load of 500 μN, the penetration depths of indenter slightly increased from 25 nm to 30 nm and the coefficient of friction varied from 0.12 to 0.20, depending on sliding scans. Depth sensing instrumented indentation experiments performed at different loading rates on specimens revealed an increasing rate-sensitivity of hardness, which concerns with a significantly small activation volume for plastic flow.

Mechanical properties of nanocrystalline nickel films deposited by pulse plating

Study on microstructure of low carbon 12% chromium stainless steel in high temperature heat-affected zone

The microstructure, texture, and formability of Nb+Ti stabilized high purity ferritic stainless steel were investigated. The interstitial element carbon and nitrogen could be fully stabilized with niobium and titanium, and the precipitates were mainly composed of TiN and NbC. By analyzing the texture in various thermomechanical processes, the intensity of α-fiber obtained during hot rolling was reduced greatly after annealing and non-uniform γ-fiber was obtained. The favorable γ-fiber was observed in cold rolled and annealed sheet, whereas the maximum value of texture is located in (554) . The formation of this shifted texture was mainly attributed to the influence of “Zener” drag and selective growth. Finally, the high purity steel showed an excellent formability, which was reflected in a marked increase in average plastic strain ratio (average of 1. 70) compared with the traditional steel sheet (average of 1.06).

Z.Y. Liu

Papers

Characterization of the solidification structure and texture development of ferritic stainless steel produced by twin-roll strip casting

Evolution of cube texture in strip-cast non-oriented silicon steels

Mechanical properties of nanocrystalline nickel films deposited by pulse plating

Study on microstructure of low carbon 12% chromium stainless steel in high temperature heat-affected zone

Microstructure, Texture, and Formability of Nb+Ti Stabilized High Purity Ferritic Stainless Steel