放电等离子烧结时间对高密度W-7Ni-3Fe合金组织性能的影响

利用放电等离子烧结技术制备高密度W-7Ni-3Fe合金,研究了烧结保温时间对合金致密度、物相、显微组织以及力学性能的影响。结果表明,在1200℃烧结5~14 min后,合金均能实现充分致密化,保温时间对相对密度影响较小。合金中的W晶粒随保温时间的延长开始尺寸变化不大,烧结11 min以上才明显长大,但大多数W晶粒尺寸仍小于5μm。烧结时间超过8min,合金中新出现一种灰色的富W组织。随保温时间延长,合金的洛氏硬度下降不大,然而抗弯强度却明显上升。合金弯曲断口形貌在较短保温时间以沿晶断裂为主,粘结相的延性撕裂和W晶粒的解理断裂随烧结时间延长逐渐增多。

Effect of holding time on microstructure and properties of W-TNi-3Fe heavy alloy fabricated by spark plasma sintering

W-TNi-3Fe heavy alloy (WHA) was fabricated by spark plasma sintering (SPS) technology. The effects of holding time on densification, phases, microstructure and mechanical properties of the alloy were investigated. When starting powders were sintered with a pressure of 50 MPa at 1200 ℃ for 5 ～ 14 min,dense W-7Ni-3Fe heavy alloy was obtained. Holding time has a lithe influence on relative density of W-7Ni-3Fe heavy ahoy. The tungsten grains grow up slowly for holding time less than 11 min and remarkable growth of grains is observed over 11 min,but most tungsten grain sizes do not exceed 5 μm. A grey W-rich phase is detected in W-7Ni-3Fe heavy alloy when the sintering time is over 8 min. Hardness of the alloy decreases slightly and bending strength increases obviously when holding time is extended. The intergranular fracture is dominant for the W-7Ni-3Fe heavy ahoy prepared with a short sintering time. The bending fracture surface of W-7Ni-3Fe heavy alloy exhibits more and more ductile tearing of binding phase and cleavage rupture of tungsten grains with increasing holding time.