块体纳米晶镍的制备及力学性能研究

Preparation and Mechanical Properties of Bulk Nanocrystalline Nickel

采用直流电弧等离子体蒸发+预压烧结法制得块体纳米晶镍。对纳米晶镍的晶粒度、孔隙率进行了表征,对其压缩强度、应变速率敏感性及压缩对晶格畸变、晶粒尺寸的影响进行了研究。结果表明,纳米晶镍的晶粒尺寸随烧结温度的升高而增大,725℃烧结时块材相对致密度达97%。压缩强度随晶粒尺寸减小而增大,且与压缩速率成正比;最大抗压断裂强度达到600MPa,表现出较低的加工硬化和良好的塑性压缩形变能力,断口为沿晶断裂;压缩会引起晶格畸变量的减小和晶粒的细化。

The bulk nanocrystalline nickel was prepared by DC arc plasma evaporation method and pre-press sintering. The grain size and porosity was characterized; the compression strength, the strain-rate sensitivity and the influence of the compression process on the grain size and lattice distortion of the specimens were investigated. The results show that the grain size increases with higher sintering temperature. At 725 ℃, the relative density of the bulk nanocrystalline nickel is 97%. The compression strength increases with smaller grain size and it is proportional to the strain rate, and the highest compression fracture strength is 600 MPa. The specimen exhibits lower sensitivity to strain rate and lower working hardening exponent. The damage mechanism of the bulk nanocrystalline nickel is intergranular fracture, and the compression leads to the decrease of the grain size and lattice distortion.