(福州大學(xué) 材料科學(xué)與工程學(xué)院， 福州 350002)
摘 要: 用熔煉法制備出具有較好塑性的Ni-石墨固體自潤滑材料， 研究了球狀石墨與片狀石墨的變形組織與性能。 結(jié)果表明： Ni-石墨合金在室溫三點彎曲實驗中可壓成近V字型而不發(fā)生脆性斷裂; 經(jīng)球化處理的鑄態(tài)試樣的延伸率為15.7％, 抗拉強(qiáng)度σb為259.5 MPa。 在850 ℃進(jìn)行鍛打變形時， 壓縮變形量達(dá)到75.8％， 可以加工成薄板材料； 變形后垂直于壓縮方向的石墨呈高密度纖維狀分布， 試樣經(jīng)變形后沿纖維方向的抗拉強(qiáng)度提高， 但韌性降低。 片狀石墨在擠壓變形過程中， 通過沿應(yīng)力取向發(fā)生轉(zhuǎn)動， 在弱結(jié)合面發(fā)生解理碎裂， 并通過解理面的相對滑動以及石墨片的彼此橋接形成長纖維狀組織； 球狀石墨在壓扁的過程中， 沿子晶間的晶界發(fā)生破裂并逐漸被拉長。
關(guān)鍵字: Ni-石墨合金； 塑性變形； 纖維狀組織； 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
