工业纯钛的室温低周疲劳行为
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摘要
采用应变控制研究了工业纯钛的室温低周疲劳行为,对循环应力-应变行为和低周疲劳寿命数据进行了分析,得到了低周疲劳的相关参数;并对疲劳组织和疲劳断口进行观察与分析。结果表明:当总应变幅为0. 5%和0. 6%时,工业纯钛在疲劳变形前期表现为循环硬化,后期发生轻微的循环软化;当总应变幅大于0. 6%时,工业纯钛在疲劳变形过程中均呈现循环硬化现象。由显微组织观察可知,在低应变幅下,位错滑移是工业纯钛主要的疲劳变形机理,孪生变形在局部高应力集中区被激活;在高应变幅下,微观变形机制以孪生为主导,伴随着滑移。疲劳断口表明工业纯钛发生多源疲劳失效,在裂纹扩展区还会呈现二次裂纹,疲劳断裂为混合型断裂。
Low-cycle fatigue behavior of commercially pure titanium( CP Ti) was investigated under strain controlled mode at room temperature. The behavior of cyclic stress-strain and low-cycle fatigue life date were analyzed and the relevant parameters for low-cycle fatigue were obtained. The microstructures after fatigue and fatigue fracture observed were analyzed. The results show that when the total strain amplitude is 0. 5% and 0. 6%,the CP Ti exhibits cyclic hardening at the early stage of fatigue deformation,and slight cyclic softening occurs at the later stage of fatigue deformation. When the total strain amplitude is larger than 0. 6%,the CP Ti exhibits cyclic hardening during fatigue deformation. It is known from microstructures observation that dislocation slip is the main mechanism of fatigue deformation and twin deformation is activated in the local high stress concentration area at low strain amplitudes; while microdeformation mechanism is dominated by twins,accompanied by slip at high strain amplitudes. Fatigue fracture indicates that the CP Ti occurs multi-source fatigue failure,and it also exhibits secondary cracks in the crack propagation zone,the fatigue fracture shows quasi-cleavage.
Low-cycle fatigue behavior of commercially pure titanium( CP Ti) was investigated under strain controlled mode at room temperature. The behavior of cyclic stress-strain and low-cycle fatigue life date were analyzed and the relevant parameters for low-cycle fatigue were obtained. The microstructures after fatigue and fatigue fracture observed were analyzed. The results show that when the total strain amplitude is 0. 5% and 0. 6%,the CP Ti exhibits cyclic hardening at the early stage of fatigue deformation,and slight cyclic softening occurs at the later stage of fatigue deformation. When the total strain amplitude is larger than 0. 6%,the CP Ti exhibits cyclic hardening during fatigue deformation. It is known from microstructures observation that dislocation slip is the main mechanism of fatigue deformation and twin deformation is activated in the local high stress concentration area at low strain amplitudes; while microdeformation mechanism is dominated by twins,accompanied by slip at high strain amplitudes. Fatigue fracture indicates that the CP Ti occurs multi-source fatigue failure,and it also exhibits secondary cracks in the crack propagation zone,the fatigue fracture shows quasi-cleavage.
引文
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[3]张士举.高纯钛的应用现状及趋势[J].科技资讯,2015,13(1):89-89.
[4]周铁柱,苏娟华,任凤章,等.工业纯钛高温拉伸断裂极限[J].金属热处理,2014,39(11):38-40.ZHOU Tiezhu, SU Juanhua, REN Fengzhang, et al. Tensile fracture limit of commercial pure titanium at high temperature[J]. Heat Treatment of Metals,2014,39(11):38-40.
[5] HTOO A T,MIYASHITA Y,OTSUKA Y,et al. Notch fatigue behavior of Tl-6Al-4V alloy in transition region between low and high cycle fatigue[J]. International Journal of Fatigue,2017,95:194-203.
[6] JOSEPH S,BANTANOUS I,LINDLEY T C,et al. Slip transfer and deformation structures resulting from the low cycle fatigue of near-alpha titanium alloy Ti-6242Si[J]. International Journal of Plasticity,2017,100:90-103.
[7] DING J,ZHANG M,YE T,et al. Microstructure stability and micro-mechanical behavior of as-cast gamma-TiAl alloy during hightemperature low cycle fatigue[J]. Acta Materialia,2018,145:504-515.
[8] GB/T 15248—2008,金属材料轴向等幅低循环疲劳试验方法[S].GB/T 15248—2008,Axial equal amplitude low cycle fatigue test method for metal materials[S].
[9]张仕朝,赵嘉祺,张建国. ZTC4(Ti-6Al-4V)铸造钛合金的室温低周疲劳行为[J].理化检验(物理分册),2013,49(3):144-147.ZHANG Shichao,ZHAO Jiaqi,ZHANG Jianguo. Low cycle fatigue behavior of ZTC4(Ti-6Al-4V)titanium alloy at room temperature[J]. PTCA(Part A:Phys. Test.),2013,49(3):144-147.
[10]王拴柱.金属疲劳[M].福州:福建科学技术出版社,1985.WANG Shuanzhu. Fatigue of metal[M]. Fuzhou:Fujian Science and Technology Press,1985.
[11] SONG X P,CHEN G L,GU H C. Low cycle fatigue behavior of co mmercial purity titanium in liquid nitrogen[J]. International Journal of Fatigue,2002,24(1):49-56.
[12] BASQUIN O H. The experimental law of endurance tests[J].Proceedings of the American Society for Testing and Materials,1910,10:625-630.
[13] COFFIN L F J. A study of the effects of cyclic thermal stresses on a ductile metal[J]. Ryūmachi,1953,22(6):419-606.
[14] E606,Annual book of ASTM standard[S].
[15]束德林.工程材料力学性能[M].北京:机械工业出版社,2015.SHU Delin. Mechanical properties of engineering materials[M].Beijing:China Machine Press,2015.
[16]谢济洲.低循环疲劳手册[M].北京:北京航空材料研究院,1991.XIE Jizhou. Low cycle fatigue manual[M]. Beijing:Beijing Institute of Aeronautical Materials,1991.
[17]周胜田,刘均,黄宝宗.钛合金TC4低周疲劳连续损伤力学研究[J].机械强度,2008,30(5):798-803.ZHOU Shengtian,LIU Jun,HUANG Baozong. Continuum damage mechanics study on low-cycle fatigue damage of Ti alloy TC4[J]. Journal of Mechanical Strength,2008,30(5):798-803.
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