打击气压对激光快速成形TC4合金剪切带形成及发展的影响

On effects of strike pressure on forming and developing of shear band in Laser Rapid Forming TC4 alloy

采用分离式霍普金森杆系统,对激光快速成形TC4合金帽型试样进行不同打击气压下的动态压缩试验.采用光学显微镜、扫描电镜、透射电镜等分析手段,研究了打击气压对其剪切带形成及发展的影响.结果表明,打击气压对激光快速成形TC4合金中所产生剪切带的形成及发展有较大的影响,随着打击气压的增大,剪切带宽度增大,且剪切带内的沿剪切方向的流线逐渐减弱;各种打击气压下,剪切带内均由细小晶粒组成,当打击气压为0.065 MPa时,剪切带内无动态再结晶晶粒,而其它气压下,剪切带内均出现了动态再结晶晶粒,且随打击气压的增大,再结晶晶粒比例增多,至气压为0.100 MPa时,剪切带内几乎由细小再结晶晶粒构成,计算显示,随打击气压的增大,剪切带内的绝热温升也随之增加.

Using the split Hopkinson bar system,the dynamic compression experiment on hat-shape sample of Laser Rapid Forming Ti-6Al-4V(LRF TC4)titanium alloy have been conducted under the different strike pressure.And effects of the strike pressure on the process of forming and developing of shear band in LRF TC4 alloy has been investigated by methods of optical microscope(OM),scanning electronic microscope(SEM)and transmission electron microscope(TEM).Analysis results show that the strike pressure has a great influence on the the process of forming and developing of shear band in LRF TC4 alloy.The width of shear band increases with the increasing of the strike pressure,and the flow line along the shear direction in the shear band gradually weakens.The shear band is composed of fine grains under different strike pressure.When the strike pressure is 0.065 MPa,there is no dynamic recrystallization grains found in shear band,while under another strike pressure in this study,dynamic recrystallization grains appears in the shear band and the proportion of recrystallized grains increases with the increase of strike pressure.When the pressure is 0.100 MPa,the shear band is almost composed of fine recrystallized grains.Calculation results shows that the adiabatic temperature rise in the shear band also increases with the increase of strike pressure.