动态冲击条件下Ti-15Mo时效钛合金的变形机制

Deformation Mechanism of Ti-15Mo Aged Titanium Alloy Under Dynamic Impact Conditions

通过固溶时效处理Ti-15Mo合金获得片层组织,采用分离式霍普金森压杆(SHPB)研究应变速率对变形机制产生的影响,结合绝热温升、显微组织和硬度分析表明:由于位错与第二相的相互作用,导致流变应力曲线发生波动。提高应变速率,一方面造成应变速率强化;另一方面促进绝热升温软化。合金温度达到379 K时,热软化效应超过应变硬化效应,变形方式由均匀塑性变形变为绝热剪切变形。绝热剪切带的宽度随切应变的增加而增大,通过亚晶旋转再结晶机制产生等轴晶粒。再结晶的界面强化导致组织硬度由高到低为:混合组织>条状组织>基体组织。时效处理抑制应力诱发孪生(TWIP)效应,造成合金较低的应变硬化能力,劣化材料的动态力学性能。

The lamellar structure of Ti-15 Mo alloy was obtained by solution aging treatment.The effect of strain rate on deformation mechanism was studied by split Hopkinson pressure bar(SHPB).Combined with adiabatic temperature rise,microstructure and hardness analysis,it is shown that the flow stress curve fluctuates due to the interaction between dislocation and the second phase.Increasing the strain rate,on the one hand,causes the strain rate to strengthen;on the other hand,it promotes adiabatic heating and softening.When the alloy temperature reaches 379 K,the thermal softening effect exceeds the strain hardening effect,and the deformation mode changes from uniform plastic deformation to adiabatic shear deformation.The width of adiabatic shear band increases with the increase of shear strain,and equiaxed grains are produced by subcrystalline rotation recrystallization mechanism.The interface strengthening of recrystallization leads to the hardness from high to low:mixed tissue>strip tissue>matrix tissue.Aging treatment inhibits the twinning induced plasticity(TWIP)effect,resulting in lower strain hardening ability of the alloy and deteriorating the dynamic mechanical properties of the material.