Papers by Keyword: Carbon Addition

Abstract: For the purpose of application for structural members such as the automobile, effect of carbon modification to the AZ91D magnesium alloy chip surface on fatigue property was examined by the rotary bending test. The carbon modification to the chip surface was quite useful for the control of the internal defect for the thick part on the thixomolding process. The depression of the internal defect by the carbon nanoparticle modification is closely related to the improvement of flowability, and that is presumed to be based on promoting the filling of the molten metal into the metal die inside. The tensile strength and elongation were respectively improved by the carbon addition. In addition, the fatigue strength also improved over 15%. This improvement of the mechanical property is based on the refinement of the crystal grain as well as the depression of the internal defects.

Abstract: Tribology tests were conducted on silicon nitride-based nanocomposites with various carbon additions to explore the effects of microstructure, the type and quantity of carbon additives and the preparation routes on the behavior. The nanocomposites consisted of Si3N4 and C in the proportions of 1 – 10 wt % carbon nanotube (CNT), or carbon black (CB), or graphite, or graphene. Specimens were produced by hot isostatic pressing. X-ray diffraction and scanning electron microscopy were used to reveal phase composition and microstructure. Unlubricated ball-on-disk tribology tests with silicon nitride counter face were carried out at room temperature in ambient atmosphere. Contact profilometer was used to profile the wear tracks. The friction coefficients of the pure Si3N4 and Si3N4 samples with 3% CNT varied between 0,77-0,81. Addition of 10% graphite and 3% CB to Si3N4 resulted in friction coefficients of 0,83 and 0,72 respectively. Si3N4 samples with 3% graphene showed distinctly lower friction levels of 0,52 and smaller scatter of the measured values. The wear track study revealed that high graphene content in the Si3N4 matrix caused relatively big wear particles and an uneven wear track.

Abstract: In order to increase critical stress for slip in Ti-Nb base shape memory alloys, strengthening by carbon additions (0.2 and 0.5mass%C) to Ti-27mol%Nb was investigated. It was found that all the alloys were  (bcc) phase at room temperature, and TiC existed in C-added alloys. The grain size was decreased with carbon content due to grain boundary pinning. Texture measurement revealed that strong {112}<110> recrystallization texture was formed in C-free alloy and that weak {001}<110> texture in C-added alloys. Tensile tests revealed that clear superelasticity appeared in C-free alloy but that stress-induced martensitic transformation seems to be suppressed by TiC in C-added alloys. The critical stress for slip was linearly increased by carbon content. Then, carbon addition affects the shape memory properties of TiNb alloys, and is effective to enhance the critical stress for slip.

Abstract: In this paper, the TiCN-based cermets were fabricated with ultrafine TiCN, metal binders and carbide additives. Different content of C and Al were separately added to eliminate the oxygen contamination. The composition of the mixture was TiCN-10Mo-20WC- 20Ni-xC/Al. Effect of the C and Al addition on microstructure and mechanical properties was investigated. Results indicated that cermets with carbon addition had higher relative density and more homogenous microstructure while the Al addition had the opposite effect. Proper addition of carbon improved the mechanical properties.

Abstract: The initial coarse grain size of 400㎛ of a as-cast AZ31 alloy was refined to 130㎛ by carbon addition method. The microstructural evolution, recrystallization, edge cracking phenomena of the coarse grained AZ31 alloy during hot rolling were investigated and compared with those of grain refined AZ31 alloy.