SPS制备多级孔结构钨骨架压缩性能及致密化行为研究

Research on the densification behavior and Compression performance of SPS prepared Tungsten skeleton with hierarchical pores structure

摘要:

以粒径分布为15-106 μm多孔球形团聚W粉为原料，采用SPS在不同烧结温度(1450℃、1500℃、1550℃)，轴向恒压40Mpa，保温5min下制备出高强度(347.8±10.6 Mpa(1450℃)、407.4±14.2 Mpa(1500℃)、543.9±8.7 Mpa(1550℃))、多级孔结构（3-10 μm\200-500 nm）W骨架。结合XRD、SEM、万能试验机等检测技术，对SPS烧结过程中粉末致密化行为、显微组织变化及力学性能进行了系统研究。结果表明: SPS可制得烧结前后物相无明显变化、孔隙率介于30%-40%、烧结颈发育完全多级孔结构钨骨架。该多级孔W骨架SPS烧结致密化过程可分为4个阶段，第一阶段为升压阶段，烧结试样相对密度随压力升高而迅速升高；第二阶段为典型的颗粒重排阶段；第三阶段烧结温度高于1000℃，烧结试样相对密度随温度的升高而升高，属于典型的烧结中期；第四阶段为烧结末期，烧结体内部高温蠕变引起致密化程度进一步提高。利用高温蠕变模型研究了该多孔球形W粉的致密化机理为纯扩散致密化，通过颈长方程确定该多孔球形钨粉在整个SPS烧结过程中的致密化机理是以体积扩散为主，晶界扩散为辅。

Abstract:

W skeleton with high strength (347.8±10.6 Mpa(1450℃), 407.4±14.2 Mpa(1500℃), 543.9±8.7 Mpa(1550℃) and hierarchical pores structure (3-10 m\200-500 nm) was prepared by SPS at different sintering temperatures (1450℃, 1500℃, 1550℃) and at axial constant pressure (40Mpa) for 5 minutes by using the particle size distribution of 15-106 m porous spherical agglomerate W powder as raw material. The densification behavior, microstructure changes and mechanical properties of SPS sintering process were systematically studied by XRD、SEM and universal testing machine. The results show that SPS can produce W skeleton have developed sintered neck and hierarchical pores structure with no significant change in phase before and after sintering and porosity of 30%-40%. The sintering densification process of W skeleton with hierarchical pores structure by SPS can be divided into four stages: the first stage is the pressure increase stage, the relative density of sintered sample increases rapidly with the increase of pressure; the second stage is a typical particle rearrangement stage; the third stage is a typical sintering metaphase, the relative density of sintered sample increases with the increase of temperature, when temperature higher than 1000℃; the fourth stage is the end of sintering, and the densification degree is further improved due to high temperature creep inside the sintered body. The densification mechanism of the porous spherical W powder was determined as Pure diffusion densification by using the high temperature creep model, and further determined volume diffusion as the main mechanism and grain boundary diffusion as the auxiliary mechanism by the neck length equation.