Research On Micro Forming Of Nanocrystaline Ni-Co Foil Material At High Temperature

Nano-materials have superplasticity for its special structure, th e research of which has become a hot spot in the field of scientific research. At the same time, the development of MEMS makes the study of micro forming more and more important. In this paper, the nanocrystalline Ni-Co foil was prepared by pulsed electrodeposition, and then studied the organizational structure and high temperature plasticity of the foil. Based on the finite element simulation of rigid punch deep drawing and 5083 AL soft-male-die deep drawing process, the forming regularity of the foil under different forming technology was studied. Through the high tempreture microarray deep drawing experiments of the foil, the superplastic forming performance of materials was studied and the influence of different forming technology and parameters on the foil microarray law of deep drawing was analyzed.Different thickness of nanocrystalline Ni- Co foil was prepared by controlling the deposition time. With the aid of scanning electron microscopy(SEM) we learned the surface of foil is smooth and density, using transmission electron microscopy(TEM), X-ray diffraction and other equipment we calculated the grain size is about 15-50 nm. The high temperature plastic performance of material was studied by high temperature tensile experiment, and when the initial strain rate was 1.67×10-3s-1and temperature was 500 ℃, the maximum elongation of material was up to 430%. Throughing the mutant strain rate method, constant K of material is 750, strain rate sensitivity coefficient m is 0.532 under this condition.Through finite element analysis, for rigid punch high temperature deep drawing, the maximum tensile stress appears in the punch and die straight fillet tangent place, which is the easy broken segment of the deep drawing parts; FOR soft-male-die(5083 AL) high temperature deep drawing, the maximize tensile stress a ppears in the transition of the straight segment to die fillet, which is the easy broken segment of the deep drawing parts.Using the 5 x5 microarray deep drawing die, the rigid-punch and soft-male-die deep drawing experiments were carried respectively under different forming scheme. FOR rigid-punch forming, the best quality parts of which the h/D is 0.67 got when the forming temperature is 500℃, forming rate is 0.025 mm/min and the thickness of the foil is 60 μm; FOR soft punch(5083 AL) forming, the best quality parts of which the h/D is 0.66 got when the forming temperature is 550 ℃, the die diameter is 0.8 mm, full load drawing number is 2 times, and the thickness of the foil is 60 μm. The thickness distribution of rigid-punch and soft-male-die forming are difference and consistent with the simulation of thickness distribution. With SEM observation, the fracture mechanism of fracture is the intergranular fracture.