Papers by Keyword: Microstructure

Abstract: A1₂OC ceramic powder was successfully synthesized via a carbothermal reduction method using Al₂O₃, B₂O₃ and activated carbon powders as raw materials. The effects of synthesis temperature on the phase transformation and micro-morphology of A1₂OC were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the content of A1₂OC in the products was increased with the increasing heating temperature. The optimized process for preparing A1₂OC was heating the mixtures at 1700 °C for 2 h in argon flow. A1₂OC particles synthesized at 1700 °C were hexagon plate-like with thickness of 5 μm and size of about 50 μm. Keywords: A1₂OC, synthesis, microstructure

Abstract: The butt welding test has been performed on QCr0.8 bronze by electron beam welding. Microstructure of the joint was examined by optical microscopy and scanning electron microscopy with EDS. Microhardness of the joint was determined to evaluate the mechanical property of the joint. The fusion zone and the heat affected zone became the weak area of the joint due to the growth of grains and the redissolve of strengthening phase. The decrease of strengthening phase has a major influence on the microhardness reduction of the joint..

Abstract: Based on the first-principles pseudo-potential plane wave method, the effect of Cr addition on the microstructure of NiTi alloys are characterized and assessed with the formation enthalpy (ΔH), binding energy (ΔE) and density of states (DOS) distribution of NiTi (Cr) crystals. The results show that the binding energy of NiTi (CrNi) is slightly smaller than that of NiTi (CrTi), but the formation enthalpy of NiTi (CrTi) is much smaller than that of NiTi (CrNi).So the Ms of NiTi alloy could be decreased by the addition of ratio for Ni/Ti. And the electronic microstucture of NiTi (CrNi) alloy are also illustrated clearly.

Abstract: The solution treatment of 6063 aluminum alloy was carried out and the influences of solution process on microstructure, strength, hardness, and electrical resistivity of 6063 aluminum alloy was analyzed. The result shows that the suitable solution treatment can improve alloy solution-degree fully, meanwhile the changes of electrical resistivity of alloy tend to be balanced. The suitable solution process for 6063 aluminum alloy is solution-treated at 520°C for 3.5h, and the strength and hardness of alloy can be enhanced extremely after aging-treatment at 200°C for 5h.

Abstract: The effect of complex adding Nd and Sm elements (0.8~4wt %) on the microstructures and properties of AZ81 magnesium alloy were studied. The results show that the microstructure of the alloy was refined obviously after complex adding Sm and Nd elements. The grain sizes were declined from 98μm to 77μm, and β(Mg17Al12) phases which had a broken network distribution in alloy were decreased. At room temperature, when the addition of Sm and Nd increased to 1.5%, 0.9% respectively, the alloy had a tensile strength of 283MPa which was 10.55% higher than the base alloy. At the temperature150°Cand175°C, the tensile strength of the AZ81 alloy with 1.0% Sm and 0.6% Nd reached 208.8MPa and 176.5Mpa respectively which was 10.01% and 8.37% higher than the base alloy respectively.

Abstract: Preparation and the characteristics of environment-friendly Ce-Ti-Mn conversion coating on aluminum alloy 6061 were investigated by XRD, FESEM, EDS, TEM and AFM in this paper. It is indicated that coating characteristics such as the surface morphologies, microstructure and corrosion resistance, are greatly influenced by the formation technology at room temperature. The constituents and their concentration, and pH value of the conversion solution have an important role on the feature of Ce-Ti-Mn conversion film, which will significantly influence on the continuity, compactness and the crystalline structure of particles of the film. The concentrations of the main salt K₂TiF₆ and oxidizer KMnO₄ have significant effect on the characteristics of the conversion coating. The Ce-Ti-Mn film grows in a lamellar way, composing of oxide and/ or hydroxide phases of Ce, Ti and Mn, some of which are amorphous. The formation mechanism of the Ce-Ti-Mn conversion coating is discussed in detail.

Abstract: Semi-solid 2024 Al alloys with strontium (Sr) addition of 0.15 wt% and 0.3 wt% were prepared by Gas Induced Semi-Solid (GISS) process. Effect of Sr addition on the microstructure and mechanical properties of the semi-solid 2024 alloy was investigated. It was found that the tensile strength and % elongation of the T6 heat treated alloy with the Sr addition were higher than those without Sr addition owing to the reduction of Mg₂Si phase formation. The semi-solid 2024 Al alloy with 0.15%Sr addition obtained the average highest tensile strength of 382 MPa and elongation of 6.45%.

Abstract: Powdery emulsion explosive (PEE) invented by Ouqi Ni at the end of 1980s is a new kind of W/O industrial explosives. It has brought industrial explosives technology into a new era. Through years of development, Model I powdery emulsion explosive has been put into large scale production in more than 70 explosive manufacturers and is widely praised by its users. Through continuous research and improvements, Model II powdery emulsion explosive with better performance, longer shelf life and considerably lower cost has been successful invented. Given that safety is one of the most important factor in production, transportation and usage of industrial explosive, this paper is to evaluate the safeness of Model II PEE in terms of mechanical sensitivity, heat sensitivity, static electricity safety, and dust explosion risks. The testing results showed Model II PEE has achieved excellent safety level.

Abstract: The7A05 aluminum alloy of the 10mm thickness was welded by the friction stir welding. The microstructure and mechanical Properties of the welded joint was researched by the optical microscope, etc. The results showed: the microstructure of the weld nugget zone and the thermal mechanically affected zone were refined as the welding speed increasing when the rotate speed is constant. As the welding speed increasing the strength of extension of the welded joint is increasing at first and then stable basically. but the yield strength had no obvious change.

Abstract: Hybrid laser-Arc welding was to weld 20 mm thickness high nitrogen austenite stainless steel plates. Microstructure, hardness, mechanical properties and fractography of welding joints were researched. The results showed that the microstructure of heat affected zone and weld metal is austenite and δ-ferrite, and the heat-affected zone of welding joints is Narrow, its softening zone is smaller, the hardness is more uniform, the tensile strength of welding joints is 93.8% of the base material, fractured in the weld zone. The tensile fractography are obviously dimple.