High Temperature Mechanical Properties of Ti(C, N)-Mo2C-Ni Cermets Studied by Internal Friction Measurements

internal friction measurements were performed on TiC0.7N0.3Mo2C-Ni metal-bonded refractory materials, in order to study how the composition and the microstructure of cermets control the mechanical properties of these materials. A free inverted torsion-pendulum was used, oscillating in the 0.2-2 Hz frequency range, up to 1273K. Isothermal I.F. spectra were measured in a forced torsion-pendulum in the 10-10-4 Hz range, and up to 1400K. One thermally activated IF. peak at 1100K (at 0.5Hz), is superimposed with a high temperature I.F. background. The amplitude of the background and the activation energy of the peak are strongly dependent on the Mo and C content in the material. Transmission electronic microscope observations give complementary results to identify the relaxation mechanisms. In the physical model proposed to describe the anelastic behaviour of these materials, the 1100K peak is attributed to the dragging of Mo atoms by dislocations in Ni-Mo-Ti alloy, while the high temperature background is associated with long distance displacements of dislocations in this binder phase. The refractory skeleton gives a contribution to the high temperature background, and to another peak at 900K. A comparison is made with I.F. measurements in WC-Co, that confirms the specific role of the metallic phase for each system

Comportement mécanique à haute température du métal dur et de différents cermets de coupe

Le développement de matériaux de coupe capables de réunir les bonnes propriétés de ténacité des WC-Co et celles de résistance à la déformation plastique des cermets Ti(C,N)-Mo2C-Ni demeure un axe de recherche important. Un projet de collaboration entre Stellram SA-Nyon (Suisse) et l’Ecole Polytechnique Fédérale de Lausanne (Suisse) est actuellement en cours et s’inscrit dans ce domaine. Les objectifs principaux résident dans l’étude des effets de la variation de différents paramètres de composition sur les microstructures frittées et sur le comportement mécanique à haute température de cermets Ti(C,N)-Mo2C-(Ni,Co) et de WC-Co. Des observations en microscopie électronique à transmission conventionnelle et analytique ont été complétées par des observations en microscopie électronique à balayage. Le comportement mécanique à haute température est étudié par des mesures de frottement intérieur et par des essais macroscopiques de flexion trois points

High Temperature Properties of TiCN-Mo2C-Co Cermets Studied by Mechanical Spectroscopy

Low frequency internal friction measurements were performed on TiC0.7N0.3-Mo2C-Co cermets in an inverted torsion-pendulum working with forced oscillations. A thermally activated high temperature background and three thermally activated peaks were observed in the internal friction spectra. Two peaks, which are stable during thermal treatments, appear (at 1 Hz) at about 1050 K and 1200 K respectively. The third peak, appearing at about 950 K, is only observed during the first heating of the as-received samples. In order to locate the relaxation phenomena, similar measurements were performed on carbide-carbonitride skeletons, in which the metallic binder phase was chemically removed. Complementary microstructural characterizations, performed by conventional TEM, allow one to identify the physical mechanisms responsible for the IF peaks and background

Microstructure and mechanical properties of Ti(C,N)-Mo2C-(Ni,Co) cermets as a function of their initial chemical composition

Extrait de : Euro ceramics V (Part 2) / sous la dir. de D. BORTZMEYER, P. ABELARD, J. BAXTER. -ISBN 0-87849-761-7. ECERS V - 5th conference and exhibition of the European Ceramic Society, Versailles, FRANCE, June 22-26 1997International audienc

TiMoCN based cermets . Part I. Morphology and phase composition

International audienc

Shared genomic segment analysis in a large high-risk chronic lymphocytic leukemia pedigree implicates CXCR4 in inherited risk

Aim: Chronic lymphocytic leukemia (CLL) has been shown to cluster in families. First-degree relatives of individuals with CLL have an ~8 fold increased risk of developing the malignancy. Strong heritability suggests pedigree studies will have good power to localize pathogenic genes. However, CLL is relatively rare and heterogeneous, complicating ascertainment and analyses. Our goal was to identify CLL risk loci using unique resources available in Utah and methods to address intra-familial heterogeneity.Methods: We identified a six-generation high-risk CLL pedigree using the Utah Population Database. This pedigree contains 24 CLL cases connected by a common ancestor. We ascertained and genotyped eight CLL cases using a high-density SNP array, and then performed shared genomic segment (SGS) analysis - a method designed for extended high-risk pedigrees that accounts for heterogeneity.Results: We identified a genome-wide significant region (P = 1.9 × 10-7, LOD-equivalent 5.6) at 2q22.1. The 0.9 Mb region was inherited through 26 meioses and shared by seven of the eight genotyped cases. It sits within a ~6.25 Mb locus identified in a previous linkage study of 206 small CLL families. Our narrow region intersects two genes, including CXCR4 which is highly expressed in CLL cells and implicated in maintenance and progression.Conclusion: SGS analysis of an extended high-risk CLL pedigree identified the most significant evidence to-date for a 0.9 Mb CLL disease locus at 2q22.1, harboring CXCR4. This discovery contributes to a growing literature implicating CXCR4 in inherited risk to CLL. Investigation of the segregating haplotype in the pedigree will be valuable for elucidating risk variant(s)