Advanced Materials Research Vols. 299-300

Abstract: The rolling texture and its distribution along thickness direction in the Al alloy 6111 sheet cold rolled by synchronous Rolling and asynchronous rolling have been investigated with orientation distribution functions. The results show that the texture distribution is asymmetric on both sides of center layer of the sheet after cross shear rolling. The orientation densities of the main texture compounds on the slow roller side are higher, but are lower on the fast rolled side. The asymmetry of the texture distribution increases with improving the velocity ratio of asynchronous rolling.

Abstract: The cold-rolled sheets of the Al-Mg-Si Alloy were annealed for recrystallization in the box furnace and the bath furnace respectively, then the microstructures were observed and the recrystallization textures were investigated with the orientation distribution functions (ODFs). The results show that after recrystallization annealing at slow heating rate the coarse a-Al grains and the strong recrystallization texture composed of Cube+nd25 components and the {011}<323> components were formed in the sheets of the Al-Mg-Si alloy, and after recrystallization annealing at rapid heating rate the fine a-Al grains and the weak or almost random recrystallization textures were formed.

Abstract: Comparative experiments on the ordinary steel fiber recycled concrete (SFRC) and roller compacted SFRC were carried out to research the fracture properties of roller compacted SFRC. The results show that compressive strength, fracture toughness and fracture energy of roller compacted SFRC increase with the increase of fiber volume fraction. Compressive strength increase with the increase of recycled aggregate replacement rate and fracture toughness decrease, however, Crack tip opening displacement has little changes and fracture energy features fluctuation with the replacement ratio of recycled coarse aggregates increasing. The rolled formed layers have significant influence on the fracture properties of SFRC. The fracture toughness of roller compacted SFRC is generally lower than ordinary SFRC and compressive strength is higher than ordinary steel fiber concrete for the same aggregate replacement ratio and fiber volume fraction. Fracture energy of roller compacted SFRC is higher than ordinary SFRC for the higher steel fiber volume ratio.

Abstract: High tensile strength Al-3Mg-0.5Sc alloy wires can be produced by a method called semi-solid continuous casting-extrusion and on-line solution process (CCES). The effects of artificial aging and the combination of the artificial aging and cold drawing on the microstructures and properties of alloy wires were respectively investigated. TEM observations reveal that a large number of dislocations and Al3Sc particles distributed in the Al-matrix of Al-3Mg-0.5Sc alloy produced by semi-solid CCES.After directly artificial aging (DAA), the tensile strength is 353MPa and elongation is 19.9%; After cold drawing following artificial aging (CDAA), the tensile strength is 378MPa and elongation is 17.7%; After artificial aging following cold drawing (AACD), the tensile strength is 435MPa and elongation is 10.4%.

Abstract: The microstructure of as-cast state and as-aged of a Cu-0.43Cr-0.22Zr-0.092Mg alloy were analysized by TEM and HRTEM, and the formation mechanics of nanophase during heat treatment were discussed. The research showed that precipitations came from the microstructure of casting alloy which adjacent streak spacing were 1.2nm after aging, which obeyed the Nishyama-Wasserman orientation relationship with the matrix.

Abstract: Based on the average atom model, the statistical values of valence electron structure (VES) parameters Δρ′, σ of homophase interface and heterpphase interface had been calculated in Cu-Zn alloy. VES parameters can characterize properties of interface bonding. The effect of Zn in the Cu matrix on the interface strengthening was discussed by the Δρ′ and σ. The calculation results showed that Δρ′ and σ values of homophase interface and heterophase interface of alloy phase were bigger than ones of Cu matrix. It was the essence of interface strenghening. The heterophase interface value σ was smaller compared with the homophase interface value σ under different Zn contents (weight percent). It was the reason that the stability of matrix was superior to that of between matrix and solid solution.

Abstract: Based on the empirical electron theory of solids and molecules (EET), the phase interface electron structure of Fe₄N/a-Fe、AlN/γ-Fe、AlN/γ-Fe-C(Al) are calculated, and the reasons that the cold shortness is resulted from nitrogen as well as the add of Al element is helpful to the removal of cold shortness are analyzed with the use of the interface conjunction factors such as,σ and. The calculated results are as follows. The discontinuous electron density difference of phase interface Fe₄N/a-Fe under the first order approximation results in the remarkable strengthening effect as well as the significant decrease in toughness and ductility, demonstrating the reason that nitrogen can cause cold shortness; as the electron density difference on AlN/γ-Fe、AlN/γ-Fe-C(Al) phase interface is very large and the continuous number of the phase interface is very small, the add of Al can hinder the growth of grain, as a result, the austenite grain is significantly refined and the removal of cold shortness caused by Fe₄N can be achieved.

Abstract: Up to now, most of work focused on the grain boundary segregation and the cold shortness caused by non-metallic element of nitrogen had been done. However, it is not clear that the reasons why the nitrogen element can generate the grain boundary segregation and the cold shortness at electron structural level. Therefore, based on the empirical electron theory of solids and molecules(EET), valence electron structures of α-Fe-N, Fe₄N and AlN were calculated, and the cold shortness generated by the nitrogen element as well as the removal mechanism of cold shortness with the help of Al element were analyzed with the phase structure factor n_A. It was found that the phase structure unit of α-Fe-N with bigger n_A firstly segregates on grain boundary，then the Fe₄N with smaller n_A on grain boundary was precipitated from supersaturated solid solution α-Fe-N, resulting in the formation of Fe₄N+α-Fe hybrid followed by the cold short in steel. However, because the value of AlN is larger than that of TiN and VN, the addition of Al element can make the cold shortness starting point decrease distinctly and thus result in the removal of segregation of nitrogen and cold shortness generated by Fe₄N. The results analyzed with the EET were in agreement with experimental fact.

Abstract: The compressive strength and elastic modulus tests for two strength grade concrete specimens are carried out at different temperatures (20°C、100°C、300°C、500°C、700°C) and different heated times (1h、2h、3h), and the compressive strength and modulus of elasticity are obtained. The effects on properties of concrete for different high temperature and heated time are compared. The test result shows that the compressive strength and modulus of elasticity of concrete reduce along with the increase of heated temperature, and the higher the strength grade of concrete is, the more notable the reduced value is. Under the condition of same temperature, the longer the heated time is, the more obvious the two values reduce. The way of heating the specimens for different time has less influence on the compressive strength and modulus of elasticity than one of resisting different heated temperature.

Abstract: The microstructure and elevated temperature mechanical behavior of as-cast, HIPed and directionally solidified NiAl-Fe(Nb) Alloys have been investigated. The results show that the microstructure of as-cast NiAl-Fe(Nb) alloy consists of dendritic regions (b) and interdendritic regions (g/g¢) with non-continuous NbNiAl(Laves) phase segregating at the interfaces of b and g/g¢ phases. The HIP processing does not alter the microstructure of as-cast alloy. The longitudinal dendritic microstructure of the DS NiAl-Fe(Nb) alloy is regular. Room temperature elongations of as-cast and HIPed NiAl-Fe(Nb) alloys are all zero, however, 0.4% for the DS alloy. The strength and elongation of the HIPed alloy are higher than that of as-cast alloy. The yield strength and ultimate strength of the DS alloy are equivalent to that of as-cast alloy, but elongation of the DS alloy is higher than that of as-cast alloy, the elongation exceed 100% at 1273K, which indicates that the DS alloy can be deformed superplastically.