Papers by Author: Zhen Zhu Zheng

Abstract: The multi-laminated Ti-(SiC_p/Al) composite was produced by hot press and subsequent hot roll bonding of Ti and SiC_p/Al foils. The microstructure evolution of the composite in reaction annealing was investigated by scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX) and X-ray diffractometer (XRD). The results show that after the reaction annealing at 1300°C for 3h, the Ti and SiC_p/Al foils were completely consumed and transformed into the TiAl composite with a microlaminated structure. The microlaminated microstructure of the composite is composed of Ti₃Al/(TiAl+Ti₅Si_3p)/Ti₅Si₃/duplex-phase (TiC+Ti₃AlC) layers. The reaction mechanism is elucidated by employing the reaction model.

Abstract: In this paper, BaPbO3(5Vol.%)/2024Al composite was fabricated by powder metallurgy method. Nanosized Pb particles were formed from the in-situ reaction between BaPbO3 and 2024Al, and mainly distributed homogeneously inside grains. The hot compression deformation of the composite at different temperatures was performed. The microstructure evolution of the 2024Al matrix and dynamic mechanical analysis (DMA) of the composite were made to investigate the effect of liquid Pb on the hot deformation. The results show that the presence of the liquid phase reduces deformation resistance by decreasing dislocation pileups, and simultaneous decrease in Young’s modulus of the composite.

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.

Abstract: In this paper, pure aluminium and Al-Cu (1%, 3% and 5% in mass fraction) alloy matrix composites reinforced with 35vol% 3Al2O32SiO2 short fibers were fabricated by a squeeze-casting technique. Interfacial structure and distribution of element of the composites were investigated by means of SEM, EPMA and TEM. The experimental results indicated that when pure aluminium was used as matrix, the interface was slick and chemical reaction occurred at the interface between amorphous SiO2 and matrix Al. When Cu element was added into the Al matrix alloy, the amorphous SiO2 on the fiber surface remained. Further more, with the increase of Cu element, the amount of the retained amorphous SiO2 increased. The interfacial reaction was inhibited due to the Cu element diffusion and enrichment towards the short fiber surface. SEM observation showed that large amount of fiber was drawn out from the matrix and some of them have been ruptured. Tensile test showed that the tensile strength of the 35vol% 3Al2O32SiO2sf/Al-Cu composite increased with the increasing of Cu content as compared with the Al2O3f/pure Al composite, the increment of the fracture strength of 3Al2O32SiO2sf/Al-Cu composite were 102%, 146% and 171%, respectively.

Abstract: Using a CO2 laser, a process of cladding Ni-base composite coating on Ti6Al4V with pre-placed B4C and NiCoCrAlY was studied. A good metallurgical bonding coating without cracks and pores was obtained in reasonable ratios of components and low energy laser process. Morphology and microstructure of the coating were analyzed with OM, XRD, SEM and EDS. It is certain that there was a reaction between B4C and Ti during in-situ producing TiB2 and TiC. The Ni-base composite coating is strengthened with TiB2 and TiC reinforcement phases. Vickers Hardness Tester measured that the average microhardness of the coating is HV1200 and it is 3.5 times of the Ti6Al4V substrate. The high hard coating containing several reinforcement phases greatly enhances wear resistance of titanium alloy.

Abstract: In-situ 5 vol% TiB whisker and TiC particulates reinforced titanium composites were fabricated by blending Ti powder and B4C particulates followed by reactive hot-pressing. The microstructure of the composites was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Hot compression test was conducted on gleeble-1500 Thermal-Mechanical Simulator. XRD results show that two kinds of reinforcements with different shapes were formed during hot-pressing: TiB short-fiber and equiaxed TiC particles. The true stress-true strain curves is shown as work hardening curves when the compression temperature below 600°C, and a stable flow stress is seen when the compression temperature above 600°C. Peak flow stress of the composites are much higher than that of the unreinforced alloy.