Papers by Author: Wei Ping Xu

Abstract: With the thermal simulated technique, the softening mechanism in heat affected zone (HAZ) of 2519 Al-Cu Alloy is studied. The results show that over aging of the precipitates leads θ' to the softening of HAZ. With the thermal cycling peak temperature increasing, the dimension of precipitates become coarse and the amount is reduced, therefore the strength and the hardness decreased. When the peak temperature is 476, the strength and the hardness are the lowest. With the peak temperature keeps on increasing, small part precipitates continue to grow. Most of fine needle-like θ' phases dissolve and separate out renewably, which is the reason that the strength and hardness are gradually enhanced.

Abstract: The Rotating Extrusion Alloying (REA) is a process which combined friction stir welding process and extrusion technology. In the REA process, dissimilar metals are mixed, cracked, and subjected to high speed, severe pressing deformation, and therefore rapidly alloy at a low temperature. The result shows that REA technology can be alloyed Al-Ti material. Its phases are mainly composed of Al and Al3Ti, which are distributed more evenly in the aluminum. After heat treatment, its phases’ types and pole figures have no significant change, but there is a trend of transition to the non-equilibrium stable phase. Small-angle grain boundaries decrease or even disappear.

Abstract: The Rotating Extrusion Alloying (REA) is a process which combined friction stir welding process and extrusion technology. In the REA process, dissimilar metals are mixed, cracked, and subjected to high speed, severe pressing deformation, and therefore rapidly alloy at a low temperature. The Al-Ti alloy has been prepared by REA. The result shows that during REA process, the original materials and the products after synthesis present high energy ball mill and from sintering the compound are avoided, and the contamination to the compound due to the contact with the surrounding atmosphere and high energy balls disappear. REA technology can be alloyed Al-Ti material. Its phases are mainly composed of Al and Al3Ti, which are distributed more evenly in the aluminum. After heat treatment, its phases’ types and pole figures have no significant change, but there is a trend of transition to the non-equilibrium stable phase. Small-angle grain boundaries decrease or even disappear.

Abstract: The effect of single pulse, electromagnetic stirring plus single pulse on the microstructures and properties of high strength Al-Cu alloy welds is investigated. The results show that the grain structure of weld under conventional MIG welding are coarse, oriented columnar grains, the ultimate tensile strength of weld joint is 286.5 MPa, the elongation rate of joint is 2.4%. The thermal gradient at the solid-liquid interface in the welding pool is decreased and the density of heterogeneous nucleation is enhanced by electromagnetical stirring plus single pulse, which resulted in the coarse and oriented columnar grains transforming to fine equiaxed grains; morphology and distribution of α(Al)-CuAl2 eutectic along the grain boundaries are improved, so it significantly improves the mechanical property of weld joint, the ultimate tensile strength of weld joint is up to 326.0 MPa, the elongation rate of joint reaches 7.8%.

Abstract: A method for analyzing wind-induced vibration and its control of transmission tower-line system in mountainous area is described. The method is applied to a real transmission line containing two self-supporting steel angle towers, 3 spans of conductors and ground lines together with insulators. Analyses are conducted for the out-of-plane wind direction, and the fluctuating wind load on tower-line system is simulated by harmony superposition method and davenport spectrum. The numerical results indicate that the wind-induced response and its control effect are mainly related to the stiffness of the towers, rather than the mounting height or the spans of the power lines. At the same time, viscoelastic dampers fixed on the main members can suppress the wind-induced displacement of the towers effectively.

Abstract: The grain orientations and microtextures in a friction–stir–welded magnesium alloy AZ80A were analyzed by Orientation Imaging Microscopy (OIM).The results showed that times random of grain orientations in the nugget zone were not strong and orientations were variety. They brought on very fine equiaxed grains. It also showed that deformation texture of {1,-1,0,4}<1,0,-1,0> was a few departure 20deg from the sample normal, The grains in the nugget zone from the base metal inherited the deformation texture of {1, -1,0,4}<1,0,-1,0> . It was concluded that re-crystallized grains in the nugget zone formed by a continuous dynamic re-crystallized mechanism.

Abstract: In the present paper, Al2TiO5-Al2O3 composites with 10, 20, 40, 60, 80, and 90 Vol. % of Al2O3 respectively were prepared by the sintering of Al2TiO5 and Al2O3 powers. The thermal expansion ratio was measured and the quenching-strength method was used to study the thermal shock-resistance performance. The thermal expansion ratio was found to increase from zero for the sample with 10-20Vol.%Al2O3 to that of 0.007% as the content of Al2O3 increased . The results of quenching-strength test showed that the residual strength of Al2TiO5-Al2O3 composites decreased with increasing of Al2O3 content and the thermal shock cycles. The Al2TiO5/Al2O3 composite with 20Vol.% Al2O3 remained a strength of 33.4MPa after three cycles and exhibited good thermal shock-resistance performance.