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Keywords:High specific strength steel Dual-phase nanostructure Strain hardening Ductility In situ high-energy X-ray diffraction a b s t r a c tWe report a detailed study of the strain hardening behavior of a Fee16Mne10Ale0.86Ce5Ni (weight percent) high specific strength (i.e. yield strength-to-mass density ratio) steel (HSSS) during uniaxial tensile deformation. The dual-phase (g-austenite and B2 intermetallic compound) HSSS possesses high yield strength of 1.2e1.4 GPa and uniform elongation of 18e34%. The tensile deformation of the HSSS exhibits an initial yield-peak, followed by a transient characterized by an up-turn of the strain hardening rate. Using synchrotron based high-energy in situ X-ray diffraction, the evolution of lattice strains in both the g and B2 phases was monitored, which has disclosed an explicit elasto-plastic transition through load transfer and strain partitioning between the two phases followed by co-deformation. The unloadingreloading tests revealed the Bauschinger effect: during unloading yield in g occurs even when the applied load is still in tension. The extraordinary strain hardening rate can be attributed to the high back stresses that arise from the strain incompatibility caused by the microstructural heterogeneity in the HSSS.

Vanadium dioxide (VO 2 ) has the interesting feature that it undergoes a reversible semiconductor-metal transition (SMT) when the temperature is varied near its transition temperature at 68°C. 1 The variation in optical constants makes VO 2 useful as a coating material for e.g. thermochromic windows, 2 while the associated change in resistivity could be interesting for applications in microelectronics, e.g. for resistive switches and memories. Due to aggressive scaling and increasing integration complexity, atomic layer deposition (ALD) is gaining importance for depositing oxides in microelectronics. However, attempts to deposit VO 2 by ALD result in most cases in the undesirable V 2 O 5 .In the present work, we demonstrate the growth of VO 2 by using Tetrakis[EthylMethylAmino]Vanadium and ozone in an ALD process at only 150°C. XPS reveals a 4+ oxidation state for the vanadium, related to VO 2 . Films deposited on SiO 2 are amorphous, but during a thermal treatment in inert gas at 450°C VO 2 (R) is formed as the first and only crystalline phase. The semiconductor-metal transition has been observed both with in-situ X-ray diffraction and resistivity measurements. Near a temperature of 67°C, the crystal structure changes from VO 2 (M1) below the transition temperature to VO 2 (R) above with a hysteresis of 12°C. Correlated to this phase change, the resistivity varies over more than 2 orders of magnitude. This work has been accepted for publication in Applied Physics Letters. The inset shows the in-situ XRD measurement from which the peak intensity was integrated.

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