(福州大学 材料科学与工程学院， 福州 350002)
摘 要: 用熔炼法制备出具有较好塑性的Ni-石墨固体自润滑材料， 研究了球状石墨与片状石墨的变形组织与性能。 结果表明： Ni-石墨合金在室温三点弯曲实验中可压成近V字型而不发生脆性断裂; 经球化处理的铸态试样的延伸率为15.7％, 抗拉强度σb为259.5 MPa。 在850 ℃进行锻打变形时， 压缩变形量达到75.8％， 可以加工成薄板材料； 变形后垂直于压缩方向的石墨呈高密度纤维状分布， 试样经变形后沿纤维方向的抗拉强度提高， 但韧性降低。 片状石墨在挤压变形过程中， 通过沿应力取向发生转动， 在弱结合面发生解理碎裂， 并通过解理面的相对滑动以及石墨片的彼此桥接形成长纤维状组织； 球状石墨在压扁的过程中， 沿子晶间的晶界发生破裂并逐渐被拉长。
关键字: Ni-石墨合金； 塑性变形； 纤维状组织； 延伸率
（School of Materials Science and Engineering, Fuzhou University,
Fuzhou 350002, China）
Abstract: The Ni-graphite solid self-lubricating material with good plasticity was prepared by melting method. An attempt was made to investigate the deformed microstructure and properties of spheroidal and flaky graphite. The results show that the Ni-graphite alloy presents nearly “V” shape in three-point bending test without brittle fracture at room-temperature, the elongation ratio of spheroidized as-cast specimen is 15.7% while the tensile strength σb is 259.5 MPa. The ingot is hot-forged at 850 ℃ to sheet with thickness reduction of 75.8%. After deformation, the graphite perpendicular to compression direction forms a high density fiber morphology, and the tensile strength along fiber direction increases accompanied with the decreasing of ductility. During the extrusion forming process, the flaky graphite rotates along the stress orientation and cleavage fracture takes place in weak interface, then the relative slip among cleavage planes and bridging of graphite flake lead to the formation of long fiber-like microstructure. Intergranular crack generates and spheroidal graphite is stretched gradually during the bruising process.
Key words: Ni-graphite alloy; plastic deformation; fiber-like microstructure; elongation ratio
