Effect of post heat treatment on the microstructure and properties of as-annealed TC4 ELI alloy
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摘要: 采用光学金相显微镜(OM)、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、室温拉伸、夏比冲击试验研究了后处理工艺对退火态TC4 ELI合金显微组织和力学性能的影响。结果表明，退火态TC4 ELI合金经520～720 ℃时效处理后发生“双态→等轴”的逆转变现象，强度呈现先升高后降低的趋势；冲击功在560 ℃降至最低后随温度升高稍有提高；时效α相的出现是冲击韧性劣化的主要原因，α2相析出的影响则较小。620 ℃时效态TC4 ELI合金经高温处理后，强度略微升高；温度升至β相区时，组织粗化造成屈服强度突降，晶界α相的出现引起塑性突降；高温处理后，时效α相消失，冲击功得到较大程度的恢复。
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关键词:
- 退火态TC4 ELI合金 /
- 后处理 /
- 显微组织 /
- 强度 /
- 冲击韧性
Abstract: The effects of post heat treatment on the microstructure and mechanical properties of annealed TC4 ELI alloy investigated by optical microscopy (OM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile and Charpy impact test at room temperature. The results show that the "bimodal → equiaxed" reverse transformation occurs in the annealed TC4 ELI alloy after aging at 520-720 ℃, and the strength increases first and then decreases. The impact toughness of the annealed TC4 ELI alloy decreases to the lowest value at 560 ℃, then increases slightly with the increase of temperature. The appearance of aging α phase is the main reason for the deterioration of impact toughness, while the precipitation of α2 phase has little effect. The strength of TC4 ELI alloy aged at 620 ℃ increases slightly after high temperature treatment. When the temperature rises to the β phase region, the coarsening of the microstructure causes a sudden drop in yield strength, and the appearance of the α phase at the grain boundary causes a sudden drop in plasticity. After high temperature treatment, the aging α phase disappears, and the impact toughness is recovered to a greater extent.-
Key words:
- annealed TC4 ELI titanium alloy /
- post heat treatment /
- microstructure /
- strength /
- impact toughness
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图 2 退火态TC4 ELI合金经不同温度处理后的金相照片
Figure 2. Microstructure of as annealed TC4 ELI alloy after different post heat treatments
图 3 退火态TC4 ELI合金经不同温度处理后的TEM照片
Figure 3. TEM images of as annealed TC4 ELI alloy after different post heat treatments
图 4 620 ℃时效态TC4 ELI合金经不同温度处理后的金相照片
Figure 4. Microstructure of as aging TC4 ELI alloy after different post heat treatments
(a)900 ℃;(b)920 ℃;(c)940 ℃;(d)980 ℃
图 5 620 ℃时效态TC4 ELI合金经不同温度处理后的TEM照片
Figure 5. TEM images of as aging TC4 ELI alloy after different post heat treatments
图 6 退火态TC4 ELI合金经不同工艺处理后的拉伸性能
Figure 6. Tensile properties of as annealed TC4 ELI alloy after different post heat treatments
图 7 退火态TC4 ELI合金经不同工艺处理后的拉伸断口形貌
Figure 7. Morphologies of tensile fracture surface of as annealed TC4 ELI alloy after different post heat treatments:
(a)520 ℃; (b) 560 ℃; (c) 620 ℃; (d) 720 ℃
图 8 时效态TC4 ELI合金经不同工艺处理后的拉伸性能
Figure 8. Tensile properties of as aging TC4 ELI alloy after different post heat treatments
图 9 620 ℃时效态TC4 ELI经不同工艺处理后的拉伸断口形貌
Figure 9. Morphologies of tensilefracture surface of as aging TC4 ELI alloy at 620 ℃ after different post heat treatments
(a)900 ℃; (b) 980 ℃
图 10 退火态TC4 ELI合金经不同工艺处理后的冲击性能
Figure 10. Impact toughness of as annealed TC4 ELI alloy after different post heat treatments
图 11 退火态TC4 ELI合金经不同工艺处理后的冲击断口形貌
Figure 11. Morphologies of impact fracture surface of as annealed TC4 ELI alloy after different post heat treatments
(a)520 ℃; (b) 560 ℃; (c) 620 ℃; (d) 720 ℃
图 12 620 ℃时效态TC4 ELI合金经不同工艺处理后的冲击性能
Figure 12. Impact toughness of as aging TC4 ELI alloy at 620 ℃ after different post heat treatments
图 13 620 ℃时效态TC4 ELI合金经不同工艺处理后的冲击断口形貌
Figure 13. Morphologies of impact fracture surface of as aging TC4 ELI alloy at 620 ℃ after different post heat treatments
(a)900 ℃; (b)980 ℃
表 1 TC4 ELI合金化学成分
Table 1. Chemical composition of TC4 ELI alloy plate %
Ti Al V N H C O Bal. 6.29 4.17 <0.0076 <0.001 <0.008 0.094 
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表 2 退火态TC4 ELI合金板材的力学性能
Table 2. 2 Mechanical properties of as annealed TC4 ELI alloy plate
Rp0.2/MPa Rm/MPa A/% Z/% aKV2/J 805 879 15.0 50 61
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