Advanced Materials Research Vols. 311-313

Abstract: Small particle size powder of Fe and Ni was used as raw materials (the particle diameter of metal injection molding (MIM) was 0.5-20μm generally) [1], and the wax-based polymer was used as binder, a new type of Fe-Ni alloy for semiconductor was prepared by the MIM. The processes which include injection debinding and sintering were studied as well as the properties. Metallographic analysis and XRD analysis showed that the alloy was a single stable organization of austenite (γ phase) whose expansion coefficient was low, and the microstructure was uniform and dense. The parts formed by MIM have high forming quality and forming precision as well as lower processing and manufacturing cost.So the MIM opened up a new way for processing small complex parts.

Abstract: This paper investigates the Isoniazid as chemical corrosion inhibitors for brass in 3.0% NaCl solution of different pH, employing polarization curves, electrochemical impedance spectroscopy(EIS), weight loss, and SEM. It is found that the inhibition efficiency of Isoniazid enhances with the increasing of the solution pH, from about 71% at pH 6.5 to 92% at pH 10.5. This improvement is attributed to the stronger adsorption of Isoniazid in alkaline solution, to prevent the occuring of the corrosion reaction of brass.

Abstract: Long time corrosion is carried out on a kind of new Ni-based super alloy used as a component of gas turbine engine, under salt-fog atmosphere at 700°C850°C for 200h. The salt solution component is 75% sodium sulfate plus 25% sodium chloride. The surface of the alloy was coated with salt solution at 150°C and aged at 700°C,750°C,800°C and 850°C for 10h, 50h, 100h and 200h, respectively. It is found that with the increase of temperature and aging time, the weight and thickness of the corrosion layer increase, and the corrosion becomes severer on the alloy surfaces. In the beginning of high-temperature corrosion, the corrosion speed increases quickly, and as prolong of corrosion aging time, corrosion speed turns to be invariable, and it is correlated to the formation of an oxidized layer by which the increasing of corrosion speed is restricted.

Abstract: The semisolid A356 alloy slurry, which was grain-refined by Y₂O₃, was manufactured by low superheat pouring. The effects of grain-refine on the morphology and the grain size of the primary phase in semisolid A356 alloy were researched. The results indicated that semisolid A356 alloy contained Y₂O₃ with particle-like and rosette-like primary phases could be prepared by low superheat pouring. The grain size and particle morphology of primary phase in semisolid A356 alloy were markedly improved by Y₂O₃. The refining mechanism of Y₂O₃ on the morphology and the grain size of the primary α phase in semisolid A356 alloy was delved.

Abstract: Microstructure and properties of Zn-xAl alloy were investigated, moreover, the strength and microstructure of the Cu/Al brazed joint had been studied. The results indicate that the massive microstructure is granular and fine when Al content is under 15wt.% in the cast microstructure of Zn-xAl filler metal. Meanwhile, the drawability properties of the filler metal is excellent. Thus, the massive microstructure become dendritic and coarse when Al content exceeds 15wt.%. At the same time, the drawability properties of the filler metal become bad. In the microstructure of the brazed joint, the interface layer exists in the interface between the Cu base metal and the brazed seam. The interface layer is mainly consisted of Cu9Al4 and CuAl IMCs. When Al content is under 15wt.%, the interface layer shape is a visibly serrated edge, so the adhesive strength between the interface layer and the brazed seam is higher and the mechanical property of the brazed joint is excellent. The brazed joint strength of Zn-15Al filler metal get highest. But the interface zone become relatively straight when Al content exceeds 15wt.%. In the meantime, the strength of the brazed joint decreases.

Abstract: The influence of gas nitriding on the wear and corrosion resistance of 40Cr steel was investigated. Gas nitriding experiments were carried out at 550°C for 2h and 10h. The microstructure and hardness gradient were observed and analyzed through metallurgical microscope and micro hardness tester. The polarization curves were scanned by the M398 Corrosion Integrated Test System. Using MG-200 high speed friction and wear testing machine did end mill test and calculated the wear rate. By scanning electron microscopy (SEM) observationing the worn surface morphologies. The results show that after different nitriding time, the specimen surface forms with nitrided layer of different thickness, and changes with the hardness decreased with the penetration depth. Furthermore, the gas nitriding treatment may change the corrosion potential positively and reduce the density of the electric current of 40Cr steel. In addition, wear mechanism of the matrix is mainly adhesive wear, but after nitriding is mainly abrasive wear. The wear rate reduces significantly.

Abstract: The electromagnetic micro-gravity simulation smelting is a new preparation technology of Al-Li alloy containing high Li. In the aluminum lithium binary system, based the principle of electromagnetic force applied on the metal alloy melt, the Al-Li alloy was smelt and cast at 0.5T and 800°C with home-made apparatus. Through composition analysis by means of XPS, surface microscopic morphology with SEM and density measurement, the results show that the low density, 10wt% of Li in Al, homogeneous lithium distribution and compact and uniform and compact microstructure Al-Li alloy can prepared by using the technique of electromagnetic simulating micro-gravity method.

Abstract: This paper focuses on the modeling of the cyclic super-elastic behaviors of SMA. Cyclic tensile experiments are performed on the NiTi SMA to test its cyclic super-elastic behaviors. A material parameter evolution equation is supposed to express the cyclic effects on the material parameters of the SMA. A cyclic constitutive equation is developed to describe the stress-strain relationship of the SMA under cyclic load. Numerical results show that the cyclic constitutive model, which includes the material parameter evolution equation and cyclic constitutive equation, well predicts the super-elastic behaviors of the SMA subjected to cyclic load.

Abstract: Hot compression tests of the homogenized Mg-Zn-Nd-Cd-Zr magnesium alloy were performed on Gleeble-1500 at temperatures between 300 °Cand 420 °C and at strain rates ranging from 0.001 to 1 s^-1 with maximum strain of 0.8. The microstructure of the experimental alloy in the hot-compression procedure at elevated temperatures was observed by OM (optical microscope) and TEM (transmission electron microscope). The results provide the experimental basis for selecting hot wrought conditions of the alloy. The peak flow stress becomes larger with the increasing strain rate at constant temperature, and gets smaller with the increasing deformation temperature at constant strain rate. The deformation activation energy increases greatly in the range of higher than 420°C, and no more change in the range of 340-380°C. The alloy can be extruded successfully at 360°C with of δ_b 310 Mpa, δ₂ of 290Mpa, and δof 16%。

Abstract: The microstructures and mechanical properties of quasicrystal reinforced Mg-Al-Zn-Y alloys with different Y and Zn contents were investigated. The results show that I-phases and Mg₁₇Al₁₂ phases form in all alloys. When Y content exceeds 1.0 at.%, the blocky Al2Y particles form, and it is disadvantageous to improve tensile strength and elongation rate. The tensile failure modes of Mg-Al-Zn-Y alloys are quasi-cleavage fracture. The tensile strength and elongation rate increase firstly and then decrease with increasing Y and Zn contents. When Y content reaches 1.0 at.%, the tensile strength and elongation rate achieve the highest values.