(中南大學 輕質高強結構材料國家級重點實驗室，長沙 410083)
摘 要: 通過分離式霍普金森桿(SHPB)和應變限位環(huán)方法實現(xiàn)90W-Ni-Fe合金在應變率6000 s-1不同應變條件下(0.15、0.25、0.45、0.6)的動態(tài)變形，并利用掃描電子顯微鏡(SEM)、透射電子顯微鏡(TEM)，電子背散射衍射(EBSD)技術及納米壓痕技術對變形后鎢顆粒的微觀組織及力學性能進行表征。結果表明：應變低于0.25，鎢顆粒主要發(fā)生均勻塑性變形，位錯滑移是其變形的主要機制；當應變達到0.45時，沖擊過程中的溫升加速鎢顆粒內位錯的重排和湮滅，導致鎢顆粒內部發(fā)生動態(tài)回復，形成大量板條狀的亞晶粒；當應變達到0.6時，試樣內部形成絕熱剪切帶，其內部組織主要由大量細小的等軸晶組成。晶粒細化導致剪切帶內的硬度(13.21 GPa)高于剪切帶外的硬度(9.16 GPa)。隨著應變的繼續(xù)增加，微裂紋在剪切帶內形核和擴展，導致90W-Ni-Fe合金斷裂失效。
關鍵字: 鎢合金；動態(tài)載荷；應變；絕熱剪切
（National Key Laboratory of Science and Technology for National Defense on High-strength Structural Materials, Central South University, Changsha 410083）
Abstract:The dynamic deformation of 90W-Ni-Fe alloy at the strain rate of 6000 s-1 and different strains (0.15, 0.25, 0.45, 0.6) was obtained by using the Split Hopkinson pressure bar (SHPB) system and strain stopping rings. Scanning electron microscope (SEM), transmission electron microscope (TEM), electron backscattering diffraction (EBSD) and nano-indentation technique were used to analyze the microstructure characteristics and mechanical properties of the deformed tungsten particles. The results show that homogeneous plastic deformation mainly occurs in the tungsten particles when the strain is lower than 0.25 and the dislocation slip is proposed as the primary deformation mechanism of tungsten alloy. As the strain level increases to 0.45, the temperature rise during the impact process accelerates the dislocation rearrangement and annihilation of tungsten particles, leading to the dynamic recovery occurs in the tungsten particles and the formation of a large number of lath subgrains. As the strain level increases to 0.6, an adiabatic shear band is formed in the specimen, the microstructure in adiabatic shear band is mainly comprised of numerous fine small grains. Grain refinement causes the nano-hardness inside the shear band (13.21 GPa) to be higher than that outside the shear band (9.16 GPa).With the strain increasing, the microcracks nucleate and expand along the shear band, resulting in the failure of 90W-Ni-Fealloy.
Key words: tungsten alloy; dynamic loading; strain; adiabatic shear
