Dynamic responses and adiabatic shear behaviors of TC17 and TC4 alloy forgings
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摘要: 利用SHPB装置研究高应变速率下TC17和TC4合金锻件的动态力学性能,并利用OM、SEM和EBSD分析两种合金的绝热剪切行为。结果表明:随着应变速率的增加,两种合金的强度均呈现出升高趋势,表现出应变速率强化效应;与TC17合金相比,TC4合金在相同应变速率下具有更大的塑性应变和动态吸收能;TC17合金经β锻造后获得网篮组织,板条状α相和残余β相形成了大量的相界面,增加了绝热剪切带(ASB)的形成位置,且ASB在扩展过程中容易出现分叉现象;TC4合金经α+β锻造后具有双态组织,等轴状初生α相具有较好的延展性,提高了合金的动态塑性变形能力,合金中排列较规则的片层状次生α相导致相界面减少,ASB的数目较少且难以分叉;在动态压缩中断条件下,TC17合金中ASB的萌生时刻早,萌生孕育能低;TC17合金的绝热剪切敏感性高于TC4合金,且两种合金的绝热剪切敏感性均随着应变速率增加而升高。Abstract: Titanium alloys are widely used in the manufacture of aero-engine blisks due to their low density, high strength, and excellent performance at medium and high temperatures. However, there are few studies on dynamic mechanical properties and adiabatic shear sensitivities of titanium alloy forgings for blisks. In this work, the dynamic mechanical properties of forged TC17 and TC4 alloys at high strain rates were examined by SHPB apparatus, and OM, SEM, EBSD were used to study the adiabatic shear behaviors of the two kinds of alloy. As the strain rate increases, the strength of both alloys increases, thus exhibiting the strain rate strengthening effect. At the same strain rate, TC4 alloy exhibits higher plastic strain and dynamic absorbed energy than those of TC17 alloy. TC17 alloy obtains a basket-weave microstructure after β forging, in which lath α-phases and residual β phases form more phase interfaces. ASBs tend to form at phase interfaces, which lead to a tendency for ASBs to bifurcate during propagating processes. TC4 alloy obtains a bimodal microstructure after α+β forging, and equiaxed primary α-phases show good ductility, which improve the dynamic plastic deformation ability. The regular arrangement of secondary α-phases results in fewer phase interfaces, leading to the difficulty in bifurcation of ASBs during propagating processes. Under dynamic interrupted compression conditions, ASBs in TC17 alloy are occurred earlier, and the localization energy of ASBs is low. Therefore, TC17 alloy has higher adiabatic shear sensitivity, and adiabatic shear sensitivities of both alloys increase with the increase of strain rates.
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Key words:
- blisk /
- α+β titanium alloy /
- high strain rate /
- dynamic absorbed energy /
- adiabatic shear band
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图 8 TC17合金在不同真应变下变形组织的OM和SEM图 (a)0.09;(b)0.14;(c)0.16;(1)试样全貌;(2)低倍变形组织及绝热剪切带;(3)高倍变形组织及绝热剪切带
Figure 8. OM and SEM images of deformation microstructures in TC17 alloy at different true strains (a)0.09;(b)0.14;(c)0.16;(1)full view of specimen;(2)low deformation microstructures and ASB;(3)high deformation microstructures and ASB
图 9 TC4合金在不同真应变下试样纵截面变形组织 (a)0.18;(b)0.22;(c)0.24;(1)试样全貌;(2)低倍变形组织及绝热剪切带;(3)高倍变形组织及绝热剪切带
Figure 9. Deformation microstructures of longitudinal-section in TC4 alloy at different true strains (a)0.18;(b)0.22;(c)0.24;(1)full view of specimen;(2)low deformation microstructures and ASB;(3)high deformation microstructures and ASB
表 1 TC17和TC4合金在2000 s−1下绝热剪切带萌生的临界应变、萌生时刻和萌生孕育能
Table 1. Critical strain(εi), initiation time(ti)and localization energy(Ei)of ASBs in TC17 and TC4 alloys at 2000 s−1
Alloy Strain rate/s−1 εi ti/μs Ei /(J·cm-3) TC17 2000 0.13 82.3 171 TC4 2000 0.19 122 272 -
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