52 research outputs found
Ammattikorkeakoulut ja yrityselämä
Yritysten on menestyäkseen ja kilpailussa pärjätäkseen kehityttävä jatkuvasti. Yritykset tarvitsevat kehitystyössään innovaatiovalmiuksia ja sparraavaa tukea.
Oulun seudulla on luotu yhteistyöfoorumeita ja kehitetty valmiuksia vastata yritysten tunnistamiin kehittämistarpeisiin. Ammattikorkeakoulujen palvelutarjonta yrityksille on nykyisellään laajaa. Palvelut voivat olla muun muassa koulutus- ja kehittämispalveluja, testaus-, mallinnus- ja tuotekehityspalveluja, yrittäjyyteen liittyviä hautomopalveluja ja tutkimuspalveluja.
Ammattikorkeakoulussa eri alojen opiskelijoiden yhteen saattaminen jo opiskeluaikana mahdollistaa innovaatioiden kehittymisen ja laaja-alaisen asioiden tarkastelemisen hallinnolliset raja-aidat ylittäen. Myös kansainvälistymisen lisäämiseen tarvitaan sekä pk- että ammattikorkeakoulusektoreilla lisää innovatiivisia avauksia. Yrityksen voivat myös hyödyntää kansainvälistymisessä ammattikorkeakouluilla jo valmiiksi olevia kansainvälisiä verkostoja.
Tuntevatko pk-yritykset riittävästi ammattikorkeakoulujen yrityksille tarjoamia mahdollisuuksia esimerkiksi kehittämistoiminnan kautta? Onko palvelujen käyttämisen kynnys riittävän matala ja ovatko palvelut mahdollisimman helposti saatavilla
Minor additions of Sn suppress the omega phase formation in beta titanium alloys
A critical characteristic of β-Ti alloys is the inevitable formation of ω-precipitates during certain heat treatments which leads to embrittlement, or even to a complete loss of ductility. Therefore, alloy design with the goal to inhibit the elementary ω-formation process is of utmost importance. Here, we propose a design strategy for prototypical β-type Ti–Cr–(Mo) alloys to alleviate this problem using only minor additions of Sn. Upon addition of Sn, we observed an extensive deceleration or even suppression of the ω-formation kinetics during isothermal ageing. Furthermore, the internal friction response of the elementary formation process indicated a decisive reduction of potential ω-nucleation sites, while the activation energy of the process remained almost unchanged. The results show, that the addition of Sn can significantly increase the width of the time–temperature process window and the long-time ageing resistance of β-Ti alloys, opening up huge opportunities for advanced alloy design and manufacturing routes.</p
Influence of Oxygen on the Kinetics of Omega and Alpha Phase Formation in Beta Ti–V
A detailed understanding of the kinetics of phase formation in β-stabilised titanium is of decisive importance for the applicability of these materials. However, the complex nature and long timescales of the various transformations, calls for specialized measurement techniques. In this work high-stability isothermal laser dilatometry is used to study the temporal volume changes associated with the various phase formation processes. Distinctly different behaviours between samples of Ti–21 at. pct V with different solute oxygen content could be detected and quantified. Temperature regimes for both diffusionless and diffusion-assisted isothermal ω-formation as well as for ω-to-α-transformation were determined. Low oxygen contents promote the diffusionless ω-formation mechanism, but retard the diffusion-assisted one as well as the ω-to-α-transformation process. The results confirm recent findings of a clear distinction between the diffusionless and diffusion-assisted isothermal ω formation modes. Modelling of the ω-phase formation applying Austin–Rickett kinetics revealed the temperature-dependent formation rates, on the basis of which the isothermal TTT-diagrams were developed which reflect the strong influence of the oxygen content.</p
Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations
In titanium alloys, the ω(hexagonal)-phase transformation has been categorized as either a diffusion-mediated isothermal transformation or an athermal transformation that occurs spontaneously via a diffusionless mechanism. Here we report a diffusionless isothermal ω transformation that can occur even above the ω transformation temperature. In body-centered cubic β-titanium alloyed with β-stabilizing elements, there are locally unstable regions having fewer β-stabilizing elements owing to quenched-in compositional fluctuations that are inevitably present in thermal equilibrium. In these locally unstable regions, diffusionless isothermal ω transformation occurs even when the entire β region is stable on average so that athermal ω transformation cannot occur. This anomalous, localized transformation originates from the fluctuation-driven localized softening of 2/3[111]β longitudinal phonon, which cannot be suppressed by the stabilization of β phase on average. In the diffusionless isothermal and athermal ω transformations, the transformation rate is dominated by two activation processes: a dynamical collapse of {111}β pairs, caused by the phonon softening, and a nucleation process. In the diffusionless isothermal transformation, the ω-phase nucleation, resulting from the localized phonon softening, requires relatively high activation energy owing to the coherent β/ω interface. Thus, the transformation occurs at slower rates than the athermal transformation, which occurs by the widely spread phonon softening. Consequently, the nucleation probability reflecting the β/ω interface energy is the rate-determining process in the diffusionless ω transformations.Tane M., Nishiyama H., Umeda A., et al. Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations. Physical Review Materials 3, 043604 (2019); https://doi.org/10.1103/PhysRevMaterials.3.043604
Structural modification by adding Li cations into Mg/Cs-TFSA molten salt facilitating Mg electrodeposition
Diffusionless isothermal omega transformation in titanium alloys driven by quenched-in compositional fluctuations
Configurational free energy in order-disorder transitions from Monte Carlo calculations for systems under external fields
A procedure for calculating the configurational free energy with the Monte Carlo simulation is presented, accounting for the case of the application of external fields. First, the free energy for the L10 ordering systems without any external fields has been evaluated for the various values of the second nearest-neighbor effective interaction, and the feature of this method has been discussed from the viewpoint of the pair correlation. Next, this method has been applied to the case of application of external fields, demonstrating the calculation of the free energy under an external stress field for the L10 phase that has a tetragonal distortion dependent on the long-range order parameter
Atomistic study of liquid fragility and spatial heterogeneity of glassy solids in model binary alloys
Abstract Fragility is a fundamental property of glass-forming liquids. Here, we evaluated the liquid fragility and structural and dynamic heterogeneity of glassy solids for four model binary alloys. The most fragile alloy exhibited the maximum dynamic heterogeneity in the mechanical unfreezing process. The local atomic order contributed to structural and dynamic heterogeneities in the glassy solid. We observed that atomic displacement significantly correlated with degrees of clustering of local atomic orders. The clustering produced during the glass-forming quenching process enhanced structural and dynamic heterogeneities, especially in fragile glass alloys. Therefore, this alloy system exhibited correlations among liquid fragility, dynamic heterogeneity in liquid alloys, and dynamic and structural heterogeneities in glassy solids. We discussed the underlying physics of the correlation based on a theoretical model for fragility. These structural and dynamic analyses also provided deeper insights into the features of structural heterogeneity in glassy solids. The alloy with the most fragility exhibited the largest difference in atomic mobility between the densely and loosely packed local atomic orders, implying the greatest heterogeneity in the degree of packing density
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