W-Ni-Fe三元系中β相时效沉淀行为及机理

高密度合金优化设计和强韧化是提高穿甲弹穿甲能力的关键。本项目研究W-Ni-Fe三元系中孪嗍毙С恋硇形盎恚处孪嗪椭屑涔沙恋硐嗟姆植肌⑿翁⒂肽赶嗟慕缑娼峁埂⑿魏撕徒峁棺涔碳盎啤⒊ご蠡砑笆Ｐ偷龋侠砜刂痞孪嗟某粱形苊馄溆泻ψ饔茫竦米罴殉恋砬炕Ч票赶妇Э墒敌炕俸辖鸬於ɡ砺刍

This project focused on the mechanical properties and microstructures of W-Ni-Fe ternary system with high Ni/Fe ratios as well as the aging behaviors and mechanisms of β phase in W-Ni-Fe ternary system. In order to avoid the harmful effect brought by β phase during slow-cooling and make good use of the strengthening effect of dispersive β phase, some certain heat treatments were employed and the relationship between the mechanical properties of alloys and the processing parameters was also involved in this study. The results showed that β phase deposit very slowly under solid-solution and traditional aging conditions, however, the kinetic of β phase can be accelerated by strain aging process and β phase mainly deposit in the inside of binder phase. During strain aging process, the hardness of W-Ni-Fe alloys with Ni/Fe smaller than 8/2 decrease monotonically and the hardness variation is dominated by the decrease of dislocations and restore and recrystallition, whereas the hardness of W-Ni-Fe alloy with Ni/Fe greater than 8/2 also decrease at the initial stage but increase to a peak at about 24 hours, the hardness variation mechanism in this alloy include the hardening mechanism which is introduced by the precipitation of β phase besides the softening mechanism. The results also showed that the deposition of β phase is a kind of nuclearation-growing transformation. The nuclearation and growth of β phase is controlled by the diffusion of tungsten atoms due to the low diffusion coefficient and the high diffusion activation energy. The high density of dislocations resulted from deformation can make the diffusion activation energy lower and provide nuclearation positions for β phase. In this way the kinetic of β phase was accelerated. What's more, the high density of dislocation provided diffusion channels for tungsten atoms. Mechanical tests showed that the optimum Ni/Fe ratios of tungsten heavy alloys changed from 7/3 under slow-cooling conditions to 9/1 under quenching conditions. The tensile strength of tungsten heavy alloys with 9/1 Ni/Fe ratios under strain aging conditions can reach 1200 MPa and the elongation can maintain 21.3%. This project made a foundation for the next generation tungsten heavy alloys with excellent mechanical properties.