Papers by Keyword: Vickers Hardness

Abstract: The effect of small additions of niobium pentoxide (Nb₂O₅) from 0 to 0.7 wt% on the zirconia toughened alumina (ZTA) ceramics sintered at 1600 °C was studied. Based on the results, the small addition of Nb₂O₅ was discovered to be able to significantly influence on phase, microstructure, and mechanical properties of ZTA ceramics. The presence of the secondary phase of Nb₂Zr₆O₁₇ as a square-shaped particle is confirmed by SEM and FESEM-EDX up to 0.5 weight percent (wt.%) of Nb₂O₅ additions. The addition of 0.3 wt.% resulted in the highest Vickers hardness value of 1500 Vickers hardness (HV). However, it was found that adding Nb₂O₅ more than 0.3 wt% causes ZTA's hardness and indentation fracture resistance (K_IFR) values to decline from 1500 HV to 1438 HV and 4.88 MPa.√m to 4.18 MPa.√m, respectively. Additionally, it was found that when the amount of Nb₂O₅ added increased, the value for bulk density climbed while porosity reduced.

Abstract: This research deals with the development of the Vickers hardness knowledge graph, mapping the example dataset in them, and exporting the data-mapped knowledge graph as a machine-readable Resource Description Framework (RDF). Modeling the knowledge graph according to the standardized test procedure and using the appropriate upper-level ontologies were taken into consideration to develop the highly standardized, incorporable, and industrial applicable models. Furthermore, the Ontopanel approach was utilized for mapping the real experimental data in the developed knowledge graphs and the resulting RDF files were successfully evaluated through the SPARQL queries.

Abstract: In this paper, the optimization of the FSW tool pin profile and shoulder-to-pin ratio is carried out to achieve high tensile strength and hardness for dissimilar Al and Mg alloys. The FSW experiment with Al and Mg alloys is designed according to Taguchi's L9 orthogonal array by varying the tool pin profile and shoulder-to-pin diameter ratio. Grey relation analysis is a multiple response optimization method used to optimize the result of the experiment. The results show that the optimum tool pin profile is a cylindrical threaded pin profile tool, and the optimum shoulder-to-pin diameter ratio is 3. The maximum tensile strength, yield strength and hardness achieved in this experiment is 147 MPa, 139 MPa, and 96 HV respectively.

Abstract: Copper-Nickel-Tin alloys have been recently developed by Hardening due to spinodal decomposition. The (Cu - 9Ni - 6Sn) system has shown promise in this direction and has been used to develop several high strength compositions. It is well known the fact that small element additions significantly modify phase transformation characteristics, the effect of adding Silicon or Silver on the Spinodal hardening in (Cu - 9Ni - 6Sn) alloy was studies close to the Spinodal cusp temperature. The presence of Silver also increased the ductility of alloy at the expense of some hardness. The effects of trace elements additions have been observed in this work with a view to improve high strength alloys as substitutes to the Copper – Beryllium alloys. The results obtained from the current research proved that adding a small amount of alloying elements with a percentage (1%) of silicon or silver to the base alloy (Cu - 9% Ni - 6% Sn), led to the stability of the mechanical properties resulting from the stability of the microstructure due to Heat treatment for hardening (Spinodal decomposition).

Abstract: ZTA is considered as one of the most popular ceramic composites that are used for cutting tools due to their excellent properties. Consistent efforts should be expanded to achieve improvements in toughness and strength, and thus help them achieve a longer tool life. However, powder compaction process has been found to be a limiting factor in the production of a defect-free ceramic pellet where the green product often ruptures immediately after the compaction process or sintering process. This may be contributed by uneven distribution of pressure load, thus affecting the particles packing and properties of final product. As a solution, the present work aims to study the effect of different compaction pressure on the physical properties of ZTA-TiO₂-Cr₂O₃ ceramic composite to establish a defect-free cutting insert. The samples were fabricated by solid state processing, subjected to pressure loads varied from 200 MPa-350MPa, followed by sintering at 1600°C for 1 hour. The sintered samples were characterized accordingly. The results showed significant enhancement in density and hardness with increasing compaction pressure from 200 MPa to 300 MPa. On the other hand, further increment of pressure deteriorates the properties of the samples. These were due to the excessive external pressure which caused a very tight compaction in the mold, resulted in elastic expansion of the compact and sliding of particles as the pressure is removed. In conclusion, ZTA-TiO₂-Cr₂O₃ subjected to 300 MPa compaction pressure showed the most optimal properties with the highest density (4.58 g/cm³) and hardness (2001 HV).

Abstract: Influence of residual welding stresses on the hardness values of the weld metal is studied. The investigations were carried out on 5V titanium alloy welded joints, obtained by electron-beam welding and argon-arc welding (TIG-welding). It is shown that the nature of the residual stresses distribution depends on the parameters of welding and affects the hardness values of the weld metal. It is shown, that the difference between the hardness values of the metal after welding and the metal after partial relief of residual stresses on the investigated alloy is up to 90 MPa, which is about 3% of the weld metal hardness level.

Abstract: In order to reduce the cost of β-type Ti alloys, the use of Fe as an alloying element has been studied. However, Fe is known to have a very high diffusion coefficient in β-Ti of about 2.6×10^-12 m²/s at 1200 K, and its behavior during heat treatment is expected to be difficult to control. By contrast, Mo, which is also a β-stabilizing element, has a diffusion coefficient of only about 2.5×10^-14 m²/s at 1200 K, i.e., roughly 100 times smaller than that of Fe^{1), 2)}. In this study, the effect of the partial substitution of Fe with Mo on the aging behavior of β-Ti alloys was investigated using X-ray diffraction, electric resistivity, and Vickers hardness measurements. Ti-Mo-Fe alloys were solution-treated by holding at 1173 K for 3.6 ks and then quenching in ice water. In the X-ray diffraction patterns for the resulting samples, only peaks associated with the β phase were identified. It was found that the electrical resistivity and Vickers hardness decreased with increasing Mo content. As the Mo-to-Fe ratio increased, the decrease in electrical resistivity and the increase in Vickers hardness occurred later during the isothermal aging process. This was due to a delay in isothermal ω-phase precipitation.

Abstract: Superduplex stainless steel alloy exhibit high mechanical and corrosion resistance, which main industrial application is in the petrochemical industry. The manufacture and maintenance of such equipment usually involve welding processes, followed by post-welded heat treatment and it often becomes impossible to apply heat treatments. Thereby, the purpose of this work is to verify the effect of a post-welded heat treatment on shielded metal arc welding in steel grade ASTM A890/A890M - grade 6A. The microstructure in the as-welded condition consisted of austenite, secondary austenite, and ferrite phases and, the post-welded heat treatment condition exhibited only austenite and ferrite. The hardness in the melt zone reached values of 300 HV after welding and, the value was reduced to 260 HV in the post-welded heat treatment condition.

Abstract: Solder alloys are important joining medium widely used in the electronics industry to connect components to printed circuit board PCB. The Sn-Pb solder alloys have been the cornerstone medium used for a long time. Unfortunately, the use of Pb was banned by the European Union due to the harmful environmental and health issues with Pb. Therefore, in this study, the Sn-50Bi and Sn-50Bi+2%TiO2 nanoparticles lead-free solder alloy is investigated based on their shear strength, Vickers hardness, and melting temperature. The investigation shows that the hypo eutectic Sn-50Bi has a low melting temperature of approximately 145°C, and the 2%TiO₂ nanoparticles reinforced Sn-50Bi has a melting temperature of around 182°C, which is lower than the traditional Sn-Pb (Tm=183 °C) and Sn-Ag-Cu (Tm=227°C). Furthermore, the developed Sn-50Bi had a Vickers hardness and shear strength of 26.81 HV and 40.78 MPa respectively, higher than the other leaded and lead-free solders. However, after the reinforcement, the hardness increased by 12% (30 HV) and a slight increase of 2.5% (42.4MPa) in shear strength. Overall, the addition of the TiO₂ nanoparticles showed a clear influence on the Sn-Bi properties. The results obtained from this study seem satisfactory to the electronic industry and the environment.

Abstract: In this study, the two types of high-strength low-alloy steels were melted and cast in a vacuum induction furnace. Phase transition temperature of HSLA steel was calculated by JMatPro software. The calculation results show that the two different types of HSLA steels which have equal phase proportions of ferrite and austenite at a temperature of approximately 820 and 800 °C in HSLA-I and HSLA-II, respectively. In addition, the effect of chemical composition on the microstructure and mechanical properties of steels were studied. The results indicate that the ultimate tensile stress value of HSLA-II samples was greater than the HSLA-I samples by about 35%, and the yield stress and breaking strength value of HSLA-II were higher than HSLA-I as well.