| 1. |
- Wei, L.Y., et al.
(författare)
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Precipitation hardening in a cast Mg-rare earth alloy
- 1992
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Ingår i: Magnesium alloys and their applications. - Oberursel : DGM Informationsgesellschaft Verlag. - 3883551848 ; , s. 335-342
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Konferensbidrag (refereegranskat)abstract
- The age hardening and precipitation behaviour of a cast Mg--1.3 rare earth alloy has been investigated. Ageing of solution treated and quenched specimens for 3 h at elevated temperatures resulted in a hardness peak for specimens aged at 250 deg C. TEM showed the sequence of precipitation in the matrix was: supersaturated solid solution - > GP zones - > beta ' (on dislocations) - > beta ; and supersaturated solid solution - > beta (formed on rare earth inclusions). It was found that the combined beta ' and beta precipitate dispersions were responsible for the peak in age hardening
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| 2. |
- Larker, Rickard, et al.
(författare)
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AEM investigation of ceramic/incology 909 diffusional reactions after joining by HIP
- 1994
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Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 29:16, s. 4404-4414
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion bonding by hot isostatic pressing (HIP) was performed between Incoloy 909 and five different ceramics. Two of the ceramics were composites made from powder mixtures of Si3N4 and either 60 vol% TiN or 50 vol% TiB2, while three were monolithic materials, namely Si3N4 with 2.5 wt% Y2O3 as a sintering additive, Si3N4 without additives, and Si2 N2O without additives. A diffusion couple geometry was developed to facilitate the preparation of thin-foil specimens for examination by analytical electron microscopy (AEM). Diffusion bonding was performed by HIP at 927°C (1200K) and 200 MPa for 4 h. The formation of reaction layers was very limited, being less than 1 μm in total layer thickness. Two reaction products were found by AEM; a continuous, very thin, (≤100 nm) layer of fine TiN crystals at the initial ceramic/metal interface, and larger grains extending about 100–500 nm into the superalloy and forming a semi-continuous layer of a G-phase suicide containing mainly nickel, silicon and niobium.
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| 3. |
- Meijer, J., et al.
(författare)
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Phase transformations by high-intensity sub-microsecond laser pulses.
- 1992
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Ingår i: Proceedings of the laser materials processing symposium, ICALEO '92. - Orlando, Fla : Laser institute of America. - 0912035498 ; , s. 228-236
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Konferensbidrag (refereegranskat)abstract
- In certain alloys, the 'laser shocking' causes work hardening, an increase in dislocation density and phase transformations. Of the materials tested, and austenitic Hadfield manganese-alloyed steel target was found to have the strongest tendency for a martensitic phase transformation. In contrast with conventional transformation hardening, there is no tempering in the case of repeated application. Whilst most material is vaporized, some surface melting will occur. The rate of re-solidification of the molten material is such that an almost completely amorphous structure results. The martensitic transformation has been confirmed by using optical, scanning and transmission electron microscopy, OM, SEM and TEM/STEM. Two different lasers, a Q-switched Ruby and a Q-switched Nd:YAG were used for the experiments. Calculations of impact/momentum, peak pressure and peak temperature were performed using the finite difference method. The model used for simulating the process has been proved to be useful in understanding the transformation mechanism.
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| 4. |
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