Advanced Materials Research Vols. 146-147

Abstract: The microstructure evolution of 780 MPa hot dip galvanized dual-phase (DP) steel at heating stages of the annealing process was analyzed using a Gleeble−3500 thermal/mechanical simulator. A multifunction continuous annealing simulator was employed to investigate the effect of annealing process on microstructure and mechanical properties of hot dip galvanized DP steel. The experimental results show that ferrite recovery and recrystallization, pearlite dissolution and austenite nucleation and growth take place in the annealing process of hot dip galvanized DP steel. The hardenability can be significantly improved by trace addition of vanadium. When the soaking temperature reaches 780 °C, the tensile strength and total elongation of DP steel can reach 785MPa and 15%, respectively. The microstructure of DP steel mainly consists of a mixture of ferrite and martensite.

Abstract: Mg96Zn2Y2 is a high strength magnesium alloy material developed by Mr. Kawamura in Japan. The name of this alloy is called as 'Kumadai Goukin'. The purpose of the present study is to evaluate the processing property of Mg96Zn2Y2 material. For this purpose, cylinder upsetting tests were performed. In addition, the marketing community of AZ31 magnesium alloy collates the information with the new material. We examined and compared the deformation resistance and ductility of the two materials. Furthermore, the dependence of deformation resistance and ductility of these materials to processing temperature and speed was evaluated [1],[2].

Abstract: Here "coercivity metering" or "coercimetry" (c.m.) means a non-destructive testing of the mechanical properties, deflected mode and fatigue capacity based on measurements of the magnetic characteristic of metal – i.e. coercivity. All listed below merits are most fully achieved when working with coercimeters (magnetic structure scopes) of SSE Company. And it is so not because the authors represent this company but rather because these devices feature a number of consumer and technical merits, which those of other manufacturers do not. Among them, the main thing is the highest clearance insensitivity i.e. when the device readings depend only on the properties of the metal, they do not depend on confounding factors, such as protective coating (paint, film, etc.) up to 6 mm (!) thick on the tested metal, or equivalent to such clearance corrosion layers, roughness, curvature of the surface, etc.

Abstract: The new concepts“crack nuclearation toughness”and “crack criterion number”given in this text were used for describing the different crack development steps and crack nuclearation critic condition and the fast developing critic condition of crack were suggested with them by means of Cottrellˊpiling up of dislocations model.The analysis pointed out that crack nuclearation toughness of brittle material is 1/2 of its fracture toughness and the criterion number of crack was a good parameter reflecting anti-crack toughness of material in crack developing process

Abstract: The objective of this research was to investigate the effect of Cobalt in as-cast sterling silver alloys used in jewellery industry on microstructure, mechanical properties, and tarnish resistance. The tarnish and corrosion resistance of sterling silver were improved with cobalt. This may be due to the grain refinement and the forming of cobalt oxide film on the surface of sliver alloy.

Abstract: More and more researchers took interests in FRP materials in civil engineering for their light weight, high strength and excellent durability performance. But common FRP rebars or plates used for reinforcing or strengthening in civil engineering are mostly made by fiber reinforced thermosetting polymer (FRSP) materials. While FRSP can not be reshaped so that many of the special shapes as bending rebar or hoop rebar cannot be easily obtained and handled at site. So, here we developed and fabricated Glass Fiber Reinforced Polypropylene (GFRPP) according to Fiber Reinforced Thermoplastic Polymer (FRTP) systems. This paper is focused on the experimental and theorial studies on the corrosion resistance of GFRPP rebar in alkali, acid and salt solution at different temperature. According to the corrosion experimental data, some durability life prediction would be concluded through FHWA method, and which may be valuable to a deeper understanding on the durability of GFRPP rebars. The results show that these kinds of GFRTP rebars have good resistance in acid and salt solution, and their mechanical properties can remain well, while bad resistance in alkali solution. As can be regarded that these FRTP rebars can be a vital support of common FRSP materials and which would play an important part in civil engineering in the future.

Abstract: This work examined the effects of Li content on the strain-hardening behaviors of three varieties of Mg−Li−Zn alloys containing approximately 6 wt%, 9 wt%, and 10 wt% of Li. Tensile tests were carried out on specimens in the directions of 0, 45 and 90° to the rolling direction. Kocks–Mecking type plots were constructed to illustrate different stages of strain-hardening. The cold-rolled Mg−6Li−1Zn (designated as LZ61) alloy sheet showed stage II and stage III strain-hardening behaviors at room temperature. The specimens of Mg−9Li−1Zn (designated as LZ91) and Mg−10Li−1Zn (designated as LZ101) alloy sheets did not show stage II strain-hardening. Higher initial strain-hardening rates were observed in the 90° direction for these alloys as a result of the cold-rolled fibrous structure affording stronger barriers to dislocation movements in this direction.

Abstract: In-situ heating transmission electron microscopy (TEM) was employed to investigate the initial stage of lamellae formation in a high Nb containing γ-TiAl based alloy. A Ti-45Al-7.5Nb alloy (at %), which was heat treated and quenched in a non-equilibrium state such that the matrix consists of ordered a2 grains, was annealed inside a TEM up to 750 °C. The in-situ TEM study reveals that g laths precipitate in the a2 matrix at ~ 750 °C possessing the classical Blackburn orientation relationship, i.e. (0001)a2 // (111)g and [11-20]a2 // <110]g. The microstructure of the in-situ TEM experiment is compared to results from ex-situ heating and subsequent TEM studies.

Abstract: The Variation of the mechanical properties of coiled tubing with increasing of the bending cycles was studied based on the fatigue bending cycle machine. The results show that the tensile strength had no significance changes during cycle fatigue. The yield strength and the force value was significantly decreased after 300 cycles, and the corresponding decreased magnitude linearly increased with the increasing of bending cycles. The changing tendency of strain hardening exponent on compression surface is different from the one on extruded surface. When the cycles increase from 100 to 600, the exponent on compression surface shows increases firstly, and decreases afterwards, However, the one on extruded surface shows decreases firstly, and increases afterwards. The yield strengths of the compression surface and extruded surface show the same changing tendency as strain hardening exponent.

Abstract: Ni-Cu-P coating was synthesized on copper substrate by electroless plating technique. The coating composition and corrosion resistance of Ni-Cu-P coating were characterized using energy-dispersive X-ray (EDX), electron probe micro-analyzer (EPMA), polarization curve (PC) and electrochemical impedance spectrum (EIS). The results show that the chemical nature of anions plays very important roles in the corrosion behavior of Ni-Cu-P coating. At a higher electrolyte concentration, Cl- and SO4 2- ions tend to promote the dissolution rate of Ni by their adsorption, while at lower electrolyte concentrations, NO3 - ions tend to dominate the dissolution rate of Ni-Cu-P coating.