Papers by Keyword: High Toughness

Abstract: Normalizing is an effective heat treatment in improving the microstructure and developing the mechanical properties of micro-alloyed steel. The normalizing parameters such as temperature and holding time are the main keys to microstructure and mechanical properties controlling. Therefore, obtaining an optimum combination of mechanical properties must be subjected to an ideal combination of these parameters. Furthermore, adjusting the optimum normalizing parameters must be considered for every chemical composition depending on the critical transformation temperatures. In this work, four micro-alloyed steel alloys containing V (0.008-0.1wt %) and Ti (0.002-0.072) were held on different normalizing temperatures for 30 minutes. The first holding temperature was carried out just above the Ac3 temperature and the second was carried out above the Ac3 by 100°C (Ac3+100°C). With the controlled normalizing condition, V-Ti-micro-alloyed steel alloy has produced an ultra-fine structure of grain size 2.2 microns and combined high strength of 725 MPa YS, 1058 MPa UTS and good ductility of 20%.

Abstract: This work aims at designing and developing low carbon steel alloys to meet the high tensile strength, high ductility and high impact toughness properties. The effect of solid solution mechanism, precipitation hardening, as well as grain refinement were developed with different Manganese content (0.78-2.36wt%) combined with Vanadium(0.008-0.1wt%) and Titanium (0.002-0.072wt%) microalloying additions. The controlled thermo-mechanical treatments and chemical compositions play a big role in developing the microstructure and the corresponding mechanical properties. Therefore, the studied chemical compositions were treated thermo-mechanically by two different ways of changing start and finish forging temperatures with subsequent air cooling. The first way by start forging from 1050 to 830oC and the second from 950 to730oC. The second way of forging process developed finer grain sizes and higher ultimate tensile strengths for all the studied steel alloys. In spite of finer grain sizes, the impact toughness value was lower in the second regime due to detrimental influence of precipitation strengthening in the ferrite. A combination of 544 MPa yield strength, 615 MPa ultimate tensile strength, 20% elongation and 138 Joule impact toughness has been attained.

Abstract: An intercritical annealing process was applied to a medium manganese steel plate (Fe-0.01C-5.3Mn-1.53Si) after the thermo-mechanical controlled processing (TMCP) and ultrafast cooling (UFC). The microstructures were observed by scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD), electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM). The retained austenite was measured by XRD and mechanical properties were measured by uniaxial tensile and impact tests. The influence of different annealing temperature was compared and the relationship between microstructures and mechanical properties was investigated. Results showed that the microstructures of the medium manganese steel plate were characterized by ultrafine grained lath-like ferrite and retained austenite and the excellent mechanical properties could be obtained at the annealing temperature of 640°C for 5 h. The volume fraction of the retained austenite reached up to 21%, which could significantly increase the elongation compared with the traditional steel plate. The mechanical property results revealed that the steel possessed adequate ultimate tensile strength of 865MPa and excellent impact energy of 121J (-20°C). The outstanding combination of strength and toughness indicates that the steel has a bright application prospect.

Abstract: The blends of ethylene vinyl acetate (EVA) and thermoplastic polyurethane (TPU) were prepared by means of blending. The mechanical properties of EVA/TPU blends and thermal stability of the extrudates were investigated. The results show that the toughness of EVA/TPU has been improved after adding TPU into EVA, and doesn’t affect the thermal stability of material.

Abstract: Shooting nails are mainly applied to fix thin reinforced concrete and steel plate, so the nails should have high hardness and high toughness. Unreasonable heat treatment process could possibly cause too high hardness and decreased toughness, leading to nail cracking and fracture in the course of production and use. Research on heat treatment process through experimental study on the nail determines the reasonable heat treatment process of nail. The feasible quenching heating temperature was 847~840 °C, and the temperature of salt bath during isothermal cooling was 292 °C. Its resultant hardness was 680HV, meeting the requirements of the use of nails. The shoot nail cracking and fracture in the course of use can be avoided effectively. The microstructure of shooting nails after heat treatment showed lower bainite, which contributed to good mechanical properties.

Abstract: Recently, semi-solid processing is paid to attention in the field of the light alloys. By this method, it is improved ductility and fatigue strength. Although, because of those mechanical properties of the elongation and toughness is not excellent, the range that can be the application to parts is limited. On the other hand, it is reported that grain refinements cause improvement of ductility and appearance of super plasticity. Then, Equal-Channel Angular Pressing (ECAP) method is reported to be effective to the sample making of a bulk and ultra fine grain in various alloys in recent years. In this study, it tried to improve ductility and durability due to making ultra fine grain in AC4CH alloys by the ECAP method, and the influence of ECAP processing on the mechanical property of AC4CH was investigated. As the result, the ductility of AC4CH has improved by ECAP processing. However, the tensile strength of AC4CH declined along with the increase in the number of passes. So, for the purpose of additional improvement of tensile strength, ECAP-Back Pressure (ECAP-BP) method that was reported to be more effective for grain refinements than ECAP method was applied to semi-solid AC4CH and compared with ECAP method. As the result, the tensile strength of AC4CH was maintained by use of ECAP-BP. Moreover, both ductility and toughness of that have been also improved.

Abstract: This paper is concert about the mechanical property of high strength and high toughness titanium alloy BTi-6554 (Ti-6Cr-5Mo-5V-4Al) bars. The results show that: in β-phase zone solid solution + aging treatment condition, the strength and fracture toughness of the alloy at room temperature can reach a higher level while inα+β)-phase solution + aging treatment condition, the plastic property is relatively high. Compared with Ti-1023 and VT22 alloy bars produced by the similar processing procedure, the alloy shows improved properties combined in strength and toughness. BTi-6554 is a new type of titanium alloy with high structural efficiency, and has a good prospect for commercial and application.

Abstract: Si3N4-TiN based multi-layer ceramics laminates have been produced. With external compressive layers, laminates with a three-fold increase in KIc over the monolithic ceramics have been realised. When external tensile layers are used in conjunction with thin internal compressive layers, energy absorbing crack deflection and bifurcation processes are observed.

Abstract: Multi-layer laminates were produced using alternating layers of Si3N4 and Si3N4+TiN. The differences in the coefficient of thermal expansions between the alternating layers lead to residual stresses after cooling. These are compressive in the Si3N4 layers and tensile in the Si3N4+TiN layers. The existence of these stresses in the laminates effect the crack propagation behaviour during failure. Different designs of laminates were produced with external layers under compression and tension exhibiting different failure mechanisms. Facture toughness was measured by SEVNB method. In systems with external layers under compression the measured fracture toughness was up to three times that of Si3N4, i.e. up to 17 MPa m1/2. In systems with external layers under tension during failure the energy absorbing effects of crack deflection and crack bifurcation were obtained. High temperature tests were performed to determine the onset temperature for residual stresses in these laminates. Micro-laminates with compressive layers of only 30 µm thickness with high strength and fracture toughness and were manufactured.