机械球磨与烧结W基材料的组织与性能

采用机械球磨与热压工艺制备了W-TiC、W-Ni、W-CNTs(碳纳米管)和W-Ni-CNTs 4种W基材料。研究结果表明,机械球磨能显著降低复合粉的晶粒尺寸和增加晶格畸变。经机械球磨后热压的样品中W-TiC的致密度最好,密度达到18.36g/cm3;W-Ni和W-CNTs的密度分别为17.97g/cm3和18.23g/cm3,具有较好的致密性;W-Ni-CNTs样品密度为15.84g/cm3,致密度略低。微观组织分析表明:添加TiC粒子可以显著改善材料的烧结行为,但晶粒较大;添加少量Ni制备的样品,不仅致密度高,而且晶粒较小;添加CNTs可以改善W的烧结行为,同时能够抑制晶粒长大和对W晶界起到强化作用;同时添加Ni和CNTs样品的致密度较低,需要对Ni和CNTs的添加量及烧结工艺条件进一步优化。结合微观组织分析与显微硬度测试结果,发现W烧结体的显微硬度不仅和材料密度有关,而且和W晶粒大小及掺杂相有关。

Microstructure and properties of W-based material fabricated by mechanical milling and hot pressing

W-based materials were fabricated at 1 500℃ for 1h under Ar atmosphere by mechanical milling and hot pressing,with 1.1%TiC,0.2%Ni,0.1%CNTs and 0.2%Ni-0.1%CNTs(in mass fraction) used as the dopants.X-ray diffraction pattern analysis reveals that the mechanical milling can significantly reduce the size of W particles and increase crystalline distortion,which can enhance the sintering behavior and mechanical properties of W-based materials.The influence of different dopants on the sintering density,morphologies and micro-hardness of sintered W-based materials was investigated.It is found that the sintering density of W-TiC is the highest with a value of 18.36g/cm3(relative density: 98.20%).The W-Ni and W-CNTs also show good densification(relative density: 93.30% and 95.89%,respectively).The W-Ni-CNTs exhibits a relative low sintering density(15.84g/cm3,relative density: 83.50%).Combining the microstructure analysis with the micro-hardness measurement,it is know that the micro-hardness of W-based materials is not only associated with their sintering density,but also the grain size and dopants.TiC and CNTs distributed at grain boundaries as dispersion phases can enhance the sintering behavior,inhibit the grain growth and improve the micro-hardness.For obtaining the desired properties of W-Ni-CNTs material,it is necessary to optimize the content of Ni,CNTs and sintering process.