Papers by Author: Fang Xin Yu

Abstract: The microstructural evolution in Cu-1.5 wt % Ti alloy aged at 400 °C was investigated by high resolution electron microscopy (HREM). The hardness and electrical conductivity of this alloy have been also characterized. The electron metallographic results showed that the sequence of the decomposition in the studied Cu-1.5 wt % Ti alloy can be summarized as follows: a modulated structure resulting from spinodal clustering → formation of clusters and then ordered fcc phase → formation of LRO β’-Cu₄Ti which distributed periodically along the <100>_Cu directions. The ordered fcc phase showed a cube-on-cube OR with matrix, while the LRO β’-Cu₄Ti showed an orientation relationship of [001]_Cu//[001]_β’ and (310)_Cu//(100)_β’. After aging for 24 h, the hardness and electrical conductivity of this alloy reached 175 HV and 25.3 % IACS, respectively. The spinodal clustering is responsible for the hardening of the alloy during the initial 30 min aging. The ordered fcc phase and β’-Cu₄Ti phase makes a significant contribution to the strengthening of the alloy during the advanced stage of aging.

Abstract: Effect of rare earth yttrium on the properties and microstructure of Cu-0.6Cr-0.15Zr-0.05Mg-0.02Si alloy was investigated. The results showed that Cu-0.6Cr-0.15Zr-0.05Mg-0.02Si alloy obtained good comprehensive performance after 80% deformation and then aging at 480°C for 1h, the hardness and electrical conductivity reached 152HV and 85.5%IACS, respectively. The aging time of Y-containing alloy for attaining peak hardness was postponed and the precipitates were finer (2-4nm) and interparticle spacing was shorter than ones of Y-free alloy. The hardness and electrical conductivity of the Y-containing alloy after 80% deformation and then aging at 480°C for 45 min reached 174HV and 82.1%IACS, respectively. The tensile fractures of the two alloys which exhibits the obvious feature of tough fracture.

Abstract: Effect of two-step deforming and aging process on the properties and structure of Cu-Cr-Zr-Mg-Si alloy was investigated. The results show under the condition of same cold deformation, two-step deforming and aging processes can improve overall performance of the alloy. The hardness obtained by two-step deforming and aging process is higher 6%-9% than that by single-step deforming and aging. The hardness and conductivity are up to 160HV and 88.1% IACS respectively after 80 % rolling and reaging at 480°C for 30min. The particles precipitate along the dislocation and pin on the dislocation during the reaging. These finer particles distribute more uniformly in the copper matrix and result in the higher strength and electrical conductivity.

Abstract: By detecting microstructures and properties of Cu-W composites, effects of powder composition, sintering temperature and compacting pressure on sintered billets were studied, and sintering mechanism of Cu-W powders was discussed. Effective rules of process parameters have been preliminarily obtained: Sintered billets of Cu-40W and Cu-50W had a low density when compacted at 200MPa, sintered below the melting point of copper, and density, hardness enlarged with sintering temperature increasing; Hardness, density, electrical conductivity of Cu-40W enlarged with compacting pressure when compacted above 600MPa, sintered at 1100°C; But when compacted at 800MPa, sintered at 1100°C, Cu-40W sintered billets had a density of 11.37g/cm3, relative density of 99.6%, closed to the theoretical value.