环境温度对16MnR钢应力疲劳的影响
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摘要
进行16MnR钢不同温度应力控制下的脉动循环试验和SEM分析。发现300℃左右是16MnR钢动态应变时效较为显著的温度,材料具有循环硬化、疲劳强度较高,循环蠕变速率较小的特点,断口具有延性脆性综合特征,循环蠕变孔洞较少,循环蠕变对材料疲劳不起主要的作用;当温度低于或高于蓝脆温度时,材料具有循环软化、疲劳强度较低、循环蠕变速率较大的特点,循环蠕变对疲劳损伤起着加速的作用,断口具有延性断裂特征,循环蠕变孔洞较多;但当温度接近材料再结晶温度时,由于发生了再结晶,使断口韧窝和蠕变孔洞变浅、变小。
Fatigue tests of 16MnR under stress control and SEM analyses at elevated temperature were conducted to investigate effect of temperature on fatigue performance.It is found that fatigue strength of material is enhanced greatly when temperature is around 300 ℃,that is to say"blue brittle"phenomenon happens which can be rationalized by dynamic strain aging effect,and material exhibits cyclic hardening character,lower velocities of cyclic creep and brittle and ductile fracture appearance with few cyclic creep cavities,so that the effect of cyclic creep on fatigue of material can be omitted.When temperature is beyond blue brittle temperature,material exhibits cyclic softening,higher velocities of cyclic creep and ductile fracture appearance with many dimples and cavities of cyclic creep.Especially when it is near to 408 ℃,the dimples and cavities of cyclic creep become flat and small due to re-crystallization.
Fatigue tests of 16MnR under stress control and SEM analyses at elevated temperature were conducted to investigate effect of temperature on fatigue performance.It is found that fatigue strength of material is enhanced greatly when temperature is around 300 ℃,that is to say"blue brittle"phenomenon happens which can be rationalized by dynamic strain aging effect,and material exhibits cyclic hardening character,lower velocities of cyclic creep and brittle and ductile fracture appearance with few cyclic creep cavities,so that the effect of cyclic creep on fatigue of material can be omitted.When temperature is beyond blue brittle temperature,material exhibits cyclic softening,higher velocities of cyclic creep and ductile fracture appearance with many dimples and cavities of cyclic creep.Especially when it is near to 408 ℃,the dimples and cavities of cyclic creep become flat and small due to re-crystallization.
引文
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[2]钱匡武,李效琦,萧林钢,等.金属和合金中的动态应变时效现象[J].福州大学学报(自然科学版),2001,29(6):8-23.
[3]A.H.Cottrell.,Dislocations and Plastic Flow in Crystals[M].Oxford University Press,Oxford,1953.
[4]陈文哲,彭开萍,钱匡武.动态应变时效对不锈钢高温强度的影响[J].机械工程学报,1992,28(2):34-38.
[5]K.Tsuzaki,T.Hori,T.Maki.Dynamic Strain Aging DuringFatigue Deformation in Type 304 Austenitic Stainless Steel[J].Materials Science and Engineering,1983,61:247-260.
[6]R.Alain,P.Violan,J.Mendez.Low Cycle Fatigue Behaviorin Vacuum of a 316L Type Austenitic Stainless Steel Between20 and 600℃,PartⅠ:Fatigue Fesistance and Cyclic Be-havior[J].Materials Science and Engineering A,1997,A229,87-94.
[7]L.A.Erasmus,L.N.Pussegoda.The strain Aging Characteris-tics of Reinforcing Steel with a Range of Vanadium Contents[J].Metallurgical Transaction,1980,11A(2):231-237.
[8]龚士弘,盛光敏,李毅,等.压力容器钢16MnR在地震载荷下的低周疲劳性能[J].钢铁,1995,30(10):48-52.
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