Papers by Author: Hong Jun Huang

Abstract: The effect of natural aging, pre-aging and paint-bake aging technology on properties of Al-Mg-Si-Cu-Zr-Er alloy for auto sheets was investigated by performance testing, microstructure observation, and differential thermal analysis. The results showed that the natural aging alloy before and after paint-bake aging presented the double peaks feature of both the mechanical properties and hardness, the maximum value of strength and hardness appeared on the second aging peak, and the paint-bake aging softening occurred. The result of differential thermal analysis showed that, compared with the artificial aging, the precipitation of β′′ phase was delayed after the natural aging; the precipitates were mainly β′′ nuclei at the paint-bake aging, and it is difficult to achieve paint-bake aging hardening. After pre-aging and nature aging treatment, the precipitates were mainly composed of β′′ phase at the paint-bake aging, and the paint-bake aging hardening was realized. The addition of Er and Zr elements accelerated the precipitation of β′′ phase, the precipitation temperature of β′′ phase reduced and the time of the first natural aging peak and pre-aging was shortened. The parameters of pre-aging treatment of alloy sheets was solution and water quenching, and then age at 170 °C for 5 min.

Abstract: In this paper, a AlMgSi alloy for sheet materials was designed on the base of 6111 aluminum alloy, the alloy sheet was fabricated by the rolling process combination of hot and cold rolling, the effect of rolling process on the microstructure of alloy was studied. The results show that different 1st rolling pass reductions of 13%, 33% and 47%, alloy microstructure changes obviously. With the increasing of 1st rolling pass reductions, the re-crystallization structure grow in quantity, re-crystallization grain more and more dense, flat, uniform, and the second phase particles are also more small, distributes more uniform. When the first cold rolled reduction is 47%, degree of grain refinement, the second phase particles fragmentation and tissue uniformity in rolling 3st state are obviously superior to the 1st state and 2st states. The deformation inhomogeneity can be overcome by improving the first reduction rate, the re-crystallization process of synchronization between surface layer and the center layer is better.

Abstract: The semi-solid compression behaviors and the microstructure of Al-Fe alloy prepared by electromagnetic stirred were investigated in the strain rate range of 5×10-3 s-1 to 5×10-1 s-1 and the temperature range of 610 to 640°C on INSTRON-5500R materials testing machine. The experimental results showed that, during the semi-solid deformation of Al-Fe alloy，the peak value of true stress decreased with elevating deformation temperature. As the deformation increased, the stress peak value of the high solid fraction alloy was tending upwards, and that of the low solid fraction was tending downwards. The peak increased with increasing the strain rate. Al-Fe alloy was sensitive to strain rate during semi-solid compression. The strain softening phenomenon would happen. The smaller strain rate, the longer softening process, the stress falling was more slowly. The strain softening was a reason that the semi-solid alloy structure was instability during deformation. The semi-solid deformational behaviors of Al-Fe alloy was bound up with deformation temperature, strain rate, and deforming extent.