Papers by Author: Guo Jian Cao

Abstract: The effect of temperature on strain softening behavior of composites with small misaligned whiskers is investigated. The results show that the temperature affects the matrix and whisker mechanical behavior and corresponding composite deformation behavior. With increasing temperature, the whisker rotation angle increases, but their breakage decreases. Meanwhile elevating temperature not only reduces the matrix flow stress and work hardening rate, but also decreases load transfer from the matrix to the whiskers and stress induced by the whisker rotation and breakage.It is found that during hot compression, strain softening behavior of composites decreases as temperature increases.

Abstract: In this work, Ni-Al-Ti-B composite powders with Ni: Al: Ti: B atom ratio of 5.7: 1.9:1:1 were prepared by using mechanical activation (MA) method. The MA processes were performed by vibration ball mill in a water-cooled chamber for 30 h. The ball-to-powder weight ratio was 10:1. In order to reduce the oxidation of the powders during milling process, ball milling was performed under an Argon atmosphere. The evolution of morphology and microstructure of Ni-Al-Ti-B composite powders were examined at different milling stages using scanning electron microscope and X-ray diffraction. Distribution of powders size was analyzed and the results showed that there were three stages for the change of powders size: (1) at the first stage, powders size increased due to more welding than fracture of the powders within 2h of MA, (2) at the second stage, particle size continuously decreased until 16h of MA due to more fracturing than welding, and (3) after 16h of MA, the particle size remained constant when welding and fracture reached an equilibrium. Calculation results according to Scherrer equation from X-ray pattern showed that the effective grain size continuously decreased with MA time. X-ray diffraction pattern confirmed that the formation of Ni and Ti solid solution during MA process of the Ni-Al-Ti-B composite powders.

Abstract: In this paper, a BaPb0.6Ce0.4O3 (BPCO)/Al matrix composite with a good anti-radiation property was fabricated by hot pressing in air for the first time. Differential scanning calorimeter (DSC) and Thermal Gravimetric (TG) analysis of the compacted blended powders were performed in air to study the oxidation behavior, by which the hot-pressing parameters were determined. Transmission electron microscope (TEM) images and X-ray diffraction pattern showed that there was an incomplete reaction between aluminum alloy matrix and BPCO particles during fabrication process. Compared with the aluminum alloy matrix, the X-ray and γ-ray absorption abilities of the composite were increased by 68.05% and 46.63%, respectively.