| 1. |
- Almer, J, et al.
(författare)
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Microstructure and thermal stability of arc-evaporated Cr-C-N coatings
- 2004
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Ingår i: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 84:7, s. 611-630
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Tidskriftsartikel (refereegranskat)abstract
- The role of C incorporation in the microstructure and thermal stability of arc-evaporated Cr-C-N coatings is explored via reactive growth in a mixed C2H4-N2 environment. C is found to react more readily than N at both the Cr cathode and the coating surfaces, so that a C2H4-to-N2 flow ratio of only 1% yields a C-to-N ratio of approximately 10% within the coatings. The as-deposited microstructures consist primarily of the δ-Cr(C, N) phase and possess high compressive residual stresses, which decrease with increasing C content. Post-deposition annealing up to 700°C results in depletion of lattice defects, and concomitant reductions in stress and coating hardness, together with phase transformations which suggest metastable phase formation during growth. Apparent activation energies for this lattice defect are found to be in the range expected for bulk diffusion of N and C (2.4-2.8 eV). The results suggest that inclusion of small amounts of C in this system offers the ability to reduce internal stresses while maintaining defect-related hardness increases, permitting growth of thicker and thus more wear-resistant coatings.
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| 2. |
- Forsblom, Mattias, et al.
(författare)
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Vibrational entropy of dislocations in Al
- 2004
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Ingår i: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 84:6, s. 521-532
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Tidskriftsartikel (refereegranskat)abstract
- The region nearest to a lattice defect must be described by an atomistic model, while a continuum model suffices further away from the defect. We study such a separation into two regions for an edge dislocation. In particular we focus on the excess defect energy and vibrational entropy, when the dislocation core is described by a cluster of about 500-100 atoms, embedded in a large discrete and relaxed, but static, lattice. The interaction between the atoms is given by a potential of the embedded-atom model type referring to Al. The dynamic matrix of the vibrations in the cluster is fully diagonalized. The excess entropy DeltaS near the core has positive and negative contributions, depending on the sign of the local strain. Typically, DeltaS/k(B) approximate to 2 per atomic repeat length along the dislocation core in fcc Al. In the elastic continuum region far from the dislocation core the excess entropy shows the same logarithmic divergence as the elastic energy. Although the work refers to a specific material and defect type, the results are of a generic nature.
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| 3. |
- Xu, Zhihui, et al.
(författare)
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An analysis of piling-up or sinking-in behaviour of elastic-plastic materials under a sharp indentation
- 2004
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Ingår i: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 84:23, s. 2367-2380
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Tidskriftsartikel (refereegranskat)abstract
- Finite-element simulation has been carried out to investigate the piling-up or sinking-in behaviour of elastic - plastic strain-hardening materials under a sharp indentation. An empirical model is proposed to relate the contact area to the material parameter E/sigma(y) and the experimental parameter h(e)/h(max). Materials with E/sigma(y)
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