Advanced Materials Research Vol. 773

Abstract: The effects of quenching at 820 °C 850 °C 940 °C and tempering at 600 °C on microstructure and properties of F550 ship plate steel were studied by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and other experimental methods. The results show that the highest value of the impact energy at-80 °C is 240 J when the steel is quenched at 850 °C and tempered at 600 °C. A full graumber of martensite-austenite (M-A) constituents which distribute in the shape of point-liner or gather among the grains, is larger compared with lamellarizing and tempering. Although the strength of the steel is higher, the value of the impact energy at-80 °C is lower and unstable. After intercritical quenching, the presence of minor ferrite and austenite grains refined could also be helpful to improve the low temperature toughness. Because polygonal ferrite (QF) is small and distributes uniformly between bainitic ferrite lathes acting as beneficial barriers to cleavage crack propagation.

Abstract: A new processing procedure was applied to an Mg alloy. This procedure involves the equal channel angular extrusion (ECAE) process and laser melting surface treatment. A commercial Mg alloy was first produced by equal channel angular extrusion (ECAE) process. Then the laser melting surfave treatment was carried out after ECAE. The effects of ECAE and laser melting on tribological properties of the alloy were investigated. Experimental results showed that the mechanical properties and tribological properties of the alloy were improved after ECAE. The laser melting surface treatment can further improve the tribological properties of Mg alloy.

Abstract: To study the malfunction cause and wear mechanism of aluminum brass in gun recoil brake, based on microscopic analysis technology, scrapped throttling ring from the repair facility as research objects, the throttling ring wear mechanism is analyzed systematically from the microscopic point integrated use of metallurgical microscope analysis, scanning electron microscopy and energy dispersive spectrometer analysis. Studies show that, as one of the vital components in recoil brake, the throttling ring made of aluminum brass is due to the composite role of erosive abrasion, chemical corrosion and cavitation damage leading to failure. The method can provide reference for the improvement of the throttling ring and the failure analysis of similar alloy parts.

Abstract: In the steel industry Sn is always regarded as harmful impurity element, one of "Five harmful elements", which affects the welding property and equality of steel product especially the equality of continuously cast bloom and causes hot brittleness, temper brittleness, crack and fracture. While Sn element also has a vital influence on free-cutting steel, electrical sheet, cast iron and stainless steel. NSSC developed ferritic stainless steel containing low Sn and Ni content improving the corrosion resistance performance and the workability significantly. So the Sn element, as cheap alternative adding element, can substitute for Cr and Ni. It's helpful to study the effect of tin in the iron and steel and develop new stainless steel products of high equality conserving chromium resources. In this way it will promote the variety and technique of stainless steel, ensure the independence on resources and conserve resources remarkably.

Abstract: The corrosion characteristic of Ti-6Al-4V alloy implanted by carbon was investigated in Hanks simulated body fluid. The results indicated that a disordered film, which was composed of TiC and Ti by XRD analysis, was formed on the surface of Ti-6Al-4V when Carbon was implanted. Electrochemical tests manifested, after implanted, the alloys corrosion potentials and increased, polarization resistance were increased, and anodic polarization current density decreased in Hanks simulated body fluid. The electrochemical properties were improved. The reason was that the disordered carbide film formed on alloys surface prevented alloying elements form dissolution and enhanced its corrosion resistance. For C implanted sample, the anodic polarization current density was increase when the alloy was abraded. It manifested that friction and abrasion conditions made corrosive environment more serious and accelerated the corrosion process. The alloys friction coefficient and abrasion rate were obviously decreased, and its hardness was increased when it was implanted C.

Abstract: This document describe accelerated corrosion test and fatigue test for the LD2 aluminum alloy test specimen, the research object is a LD2 aluminum alloy test-piece which has crack in the corrosion pit, the crack initiation life in the area of Corrosion pit has been defined, the influence of the Corrosion on the crack initiation life in corrosion pit area has been researched. Finally, the simulation of crack propagation for the LD2 aluminum alloy test-piece has been made. By comparing, the result of simulation is more conservative than the actual test value.

Abstract: Ceramic coatings were fabricated on casting aluminum-copper alloy through micro-arc oxidation by mixing Ce(SO₄)₂ into the silicate electrolyte. The effects of Ce(SO₄)₂ additive on the ceramic coatings were analyzed by means of SEM, EDX, XRD, hardness and corrosion tests. The results show that Ce(SO₄)₂ effectively promoted the reaction of the MAO coating surface, increased the thickness and hardness of the coating and enhanced the corrosion-resisting property. The optimal addition amount of Ce(SO₄)₂ in the electrolyte is 0.2g/L.

Abstract: A non-chromate conversion coating was prepared from molybdate based bath on the surface of Zn-5%Al hot dip galvanized steel. The influence of the preparation conditions such as temperature, bath pH and treating time on the corrosion resistance of the obtained conversion coating was investigated. The corrosion performance of the film was researched using electrochemical technique in 3.5%NaCl. The results indicate that the anodic branch of the polarization curves present in passivation character. Electrochemical impedance spectroscopy (EIS) illustrate that the radius of the capacity impedance for conversion coating varies distinctly according to the preparation condition. The surface morphology was observed using scanning electron microscopy (SEM), and the results show that the surface of Zn-5%Al hot dip galvanized steel present in eutectic feature after conversion coating treatment. The chemical composition of the coating was detected by energy dispersive X-ray (EDX), and the results illustrate that the conversion coating is composed of Zn, Al , O, P and Mo.

Abstract: A 3D realistic microstructure based computational homogenization model is proposed, in order to determine the temperature dependent effective coefficient of thermal expansion of particle reinforced metal matrix composites The model employed three-dimensional realistic microstructures with different domain sizes, where particles had random shape, sharp edges and were randomly distributed. The unit cell microstructure based model and classical analytical models were also presented for comparison. As an illustration of the model, a 17% vol. SiC_p reinforced 2124Al composite was investigated. Its minimum RVE size is found to be δ = 15, where δ is called the size ratio and defined by the ratio between the side length of microstructure and the mean particle radius.

Abstract: The Article through comparing commonly materials in civil construction, analyze the application prospects of New Building Material-- Recombinant bamboo. After counting experiment dates, at the part of Recombinant bamboo’s properties of material and mechanical, construction technology and production efficiency conversion, the article put forward the feasibility and necessity of the development of Recombinant bamboo building materials in southern China.