Wei GUO
,
Yaping ZONG
,
Gang WANG
,
Liang ZUO
材料科学技术（英）
The effects of applied tensile strain on the coherent α2 →O-phase transformation in Ti-Al-Nb alloys are explored by computer simulation using a phase-field method. The focus is on the influence of the applied strain direction on the microstructure and volume fraction of the O-phase precipitates. It is found that altering applied strain direction can modify microstructure of Ti-25Al-10~12Nb (at.~pct) alloy duringα2 →O-phase transformation effectively and full laminate microstructure in the Ti-25Al-10Nb (at. pct) alloy can be realized by an applied strain only along the direction 30° away from theα2 phase <10 0> in magnitude equivalent to the stress-free transformation strain. The simulation also shows that not only the magnitude of applied strain but also the applied strain direction influences the O-phase volume fraction and the effect of strain direction on the volume fraction is up to 25%.
关键词:
Phase field simulation
,
null
,
null
M.M.El-Sayed Seleman
,
Xudong SUN
,
Liang ZUO
,
K.A.Khalil
材料科学技术（英）
Alumina-(0 similar to 20 vol. pct) iron composites were fabricated by hot-pressing of well-mixed-alumina and iron powders at 1400 degreesC and 30 MPa for 30 min. Hot-pressed bodies with nearly theoretical density were obtained for addition up to 10 vol. pct Fe, but relative density decreased gradually with further increase in Fe addition. The materials exhibit a homogeneous dispersion of Fe. Fracture strength of the composites exhibits a maximum value of 604 MPa at 15 vol. pct Fe, which is 1.5 times that of alumina alone. Fracture toughness increases with the increase in Fe content, reaching 7.5 MPa.m(1/2) at 20 vol. pct Fe. The theoretical values of fracture toughness was calculated and compared with the experimental one. Toughening mechanisms of the composites are also discussed.
关键词:
Min XU
,
Minxiu QUAN
,
Zhuangqi HU
,
Y
,
ong WANG
,
Liang ZUO
材料科学技术（英）
Fe62Co8-xCrxZr6Nb4B20(x=0–4 at. pct) metallic glasses show high thermal stability with a maximum supercooled liquid region of about 84.8 K. The addition of 2 at. pct Cr causes the extension of the supercooled liquid region remarkably, leading to the enhancement of thermal stability and glass-forming ability. The crystallization of the Fe-based glassy alloys takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as α-Fe, Fe2Zr and ZrB2. The long-range atomic rearrangements required for the precipitation of the multiple crystalline phases seem to play an important role in the appearance of the large supercooled liquid region through the retardation of the crystallization reactions. The Fe-based alloys exhibit soft ferromagnetic properties. The saturation magnetization decreases with increasing Cr content while the saturated magnetostriction increases as a function of Cr content. There is no distinct change in the saturation magnetization and coercive force with annealing temperature below the crystallization temperature. The devitrification gives rise to a considerable enhancement in both δs and Hc.
关键词:
Cr addition
,
null
,
null
Gang LIU
,
Liang ZUO
,
Fu WANG
,
Xiang ZHAO
,
Zhide LIANG
材料科学技术（英）
The texture inhomogeneity in cross shear rolled grain oriented Si steel was investigated by means of the through thickness texture analysis. For the chosen rolling reductions (55%, 66.5%) and mismatch speed ratios (1.0, 1.1, 1.3), the deformation textures in various thickness layers consist of three major components, i.e. strong g-fiber, medium a-fiber and weak h-fiber, and they show an asymmetrical distribution throughout the thickness. The effect of reduction on the texture gradient is found to be more significant at and near the center layer; however, the effect of mismatch speed ratio is less important. In most cases, a strong {111}<112> texture component appears in the subsurface layers, that may favour the formation of a sharp Goss texture during the subsequent annealing.
关键词:
Cross shear rolling
,
null
,
null
Y
,
ong LIU
,
Chungang WANG
,
Qiwu JIANG
,
Tong HE
,
Liang ZUO
材料科学技术（英）
The cold rolling deformation textural evolution of an interstitial-free (IF) steel sheet is investigated by experiment and simulation. The microstructure of the IF steel is observed by transmission electron microscopy (TEM). The relationship between the deformation behavior of individual grain and the grain orientation are connected by Taylor factor M. The results show that the grains with higher Taylor factor are deformed slighter than those with lower ones. By considering the heterogeneous deformation, the texture simulation result can be greatly improved.
关键词:
IF steel
,
null
,
null
,
null
Yaping ZONG
,
Liang ZUO
材料科学技术（英）
A concept of microstructure design for materials or materials microstructure engineering is proposed. The argument was suggested based on literature review and some our new research work on second phase strengthening mechanisms and mechanical property modeling of a particulate reinforced metal matrix composite. Due to development of computer technology, it is possible now for us to establish the relationship between microstructures and properties systematically and quantitatively by analytical and numerical modeling in the research scope of computerization materials. Discussions and examples on intellectual optimization of microstructure are presented on two aspects: grain boundary engineering and optimal geometry of particulate reinforcements in two-phase materials.
关键词:
Microstructure design
,
null
,
null
Xiang ZHAO
,
Zhuochao HU
,
Liang ZUO
材料科学技术（英）
The effects of an electric field on AlN precipitation and recrystallization texture were investigated. Cold-rolled 08Al killed steel sheets were annealed at 550℃ according to the two-step processes, for various maintaining times, with and without applying an electric field. It was found that the electric field promotes the precipitation of the second phase (AlN particles), strengthens the γ-fiber and weakens the γ-fiber texture component in the recrystallized specimens. A possible explanation for the reinforcement of α-fiber texture by the electric field is that the second phase AlN particle promotes the growth of α-fiber at the expense of differently oriented grains.
关键词:
Electric field annealing
,
null
,
null
,
null
M.M.El-Sayed Seleman
,
Xudong SUN
,
Liang ZUO
材料科学技术（英）
Thermal shock behaviour was investigated for two morphologically different composites comprising an alumina matrix and 20 vol. pct Fe particles for a wide range of quenching temperature differences (∆T=100~800°C) and compared to a monolithic alumina. The retained strength and critical quenching temperature difference, ∆Tc, of the two composites were a significant improvement over the values for the respective monolithic alumina. Crack lengths and densities were shown to be greater for the alumina than for the two composites at all quenching temperature differences. The thermal shock resistance parameters for monolithic alumina and the two composites were calculated according to their mechanical and physical properties. The calculated results agree well with the experimental one and indicate possible explanations for the differences in thermal shock behaviour.
关键词:
Alumina-iron composite
,
null
,
null
M.M.El-Sayed Seleman
,
Xudong SUN
,
Liang ZUO
材料科学技术（英）
Two morphologically different composites comprising an alumina matrix and 20 vol. pct Fe particles have been fabricated by hot pressing technique. Two kinds of microstructures, i.e. a dispersive distribution of Fe particles and a network distribution of Fe particles in alumina matrix, have been produced. Both composites are tougher than the virgin alumina matrix. The fracture toughness of the composite with a network microstructure is much higher than the composite with a microstructure of dispersed particles. For the particulate dispersion microstructure, the main limitation to the toughening is the lack of plastic deformation of the ductile Fe due to the pull out of Fe particles, indicating weak bonding at the Al2O3/Fe interface. For the network microstructure composite, the gauge length of the ductile phase is much larger, allowing the ductile Fe to be stretched to failure between the crack faces. The weak bonding at Al2O3/Fe interface can promote partial debonding and contribute further to toughening in the network microstructure composite.
关键词:
