工程科学学报.第43卷.第5期：656-662.2021年5月 Chinese Journal of Engineering,Vol.43,No.5:656-662,May 2021 https://doi.org/10.13374/j.issn2095-9389.2020.04.01.003;http://cje.ustb.edu.cn 应变幅对H13热作模具钢等温疲劳行为的影响 朱振强，宁辉，左鹏鹏，吴晓春四 上海大学材料科学与工程学院，上海200444 ☒通信作者，E-mail:wuxiaochun(@shu.edu.cn 摘要对H13热作模具钢试样进行6O0℃等温疲劳实验，通过显微维氏硬度计、金相显微镜(OM)、超景深显微镜和扫描 电子显微镜(SM)等设备研究了0.7%，0.9%和1.1%三种不同应变幅对疲劳行为的影响.结果表明：应力应变滞后回线呈现 对称性，应变幅越大，滞回环面积越大.H13钢在实验中呈现循环软化的特征，应变幅越大，疲劳寿命越短，1.1%应变幅试样 寿命约为0.7%应变幅试样的612%.应变幅的增加对裂纹萌生和扩展起促进作用，1.1%应变幅试样裂纹扩展最明显.高温 非真空实验条件下，材料表面产生的氧化物也会促进裂纹扩展.疲劳后试样微观组织发生明显的长大和粗化，较大应变幅对 碳化物析出有更大的助力，还会加速材料软化.有应变幅试样显微硬度远低于无应变幅试样 关键词H13热作模具钢；等温疲劳：疲劳行为；应变：碳化物 分类号TG142.1 Effect of strain amplitude on the isothermal fatigue behavior of H13 hot work die steel ZHU Zhen-qiang,NING Hui.ZUO Peng-peng,WU Xiao-chun School of Material Science and Engineering,University of Shanghai,Shanghai 200444,China Corresponding author,E-mail:wuxiaochun@shu.edu.cn ABSTRACT Thermal fatigue cracking is the main failure mode of hot work die steel during die casting and hot forging.Thermal fatigue cracking accounts for a large proportion of mold failures and seriously affects the service life of the mold.Because of the high maintenance and replacement costs,thermal fatigue failure will cause substantial financial losses to the enterprise.Therefore,analyzing the fatigue behavior of hot work die steel at high temperatures is of significance in scientific research and engineering applications.H13 hot work die steel is widely used in die casting and hot forging because of its excellent high-temperature performance and toughness.In this study,a 600 Cisothermal fatigue test was conducted on H13 hot work die steel samples.The effect of three different strain amplitudes of 0.7%,0.9%,and 1.1%on the isothermal fatigue behavior was analyzed using a micro Vickers hardness tester, metallographic microscope,microscope with a superwide depth of field,and scanning electron microscope.Results show that the stress-strain hysteresis loop is symmetric.The larger the strain amplitude is,the larger the area of the hysteresis loop.H13 hot work die steel exhibits the cyclic softening behavior during the experiment.The larger the strain amplitude,shorter is the fatigue life.The fatigue life of the sample with the strain amplitude of 1.1%is approximately 61.2%of that of the sample with the strain amplitude of 0.7%.The increase in the strain amplitude promotes the initiation and propagation of cracks,and the propagation of cracks on the sample with the strain amplitude of 1.1%is the most obvious.Under high-temperature and non-vacuum experimental conditions,oxide on the surface of the material promotes crack growth.The microstructure of the sample under isothermal fatigue grows and coarsens.The large strain amplitude not only supports carbide precipitation but also accelerates cyclic softening of the material.The microhardness of samples with strain amplitude is lower than that of samples without strain amplitude. 收稿日期：2020-04-01 基金项目：国家重点研发计划资助项目(2016YFB0300400,2016YFB0300404)应变幅对 H13 热作模具钢等温疲劳行为的影响 朱振强，宁    辉，左鹏鹏，吴晓春苣 上海大学材料科学与工程学院，上海 200444 苣通信作者，E-mail: wuxiaochun@shu.edu.cn 摘    要    对 H13 热作模具钢试样进行 600 ℃ 等温疲劳实验，通过显微维氏硬度计、金相显微镜（OM）、超景深显微镜和扫描 电子显微镜（SEM）等设备研究了 0.7%，0.9% 和 1.1% 三种不同应变幅对疲劳行为的影响. 结果表明：应力应变滞后回线呈现 对称性，应变幅越大，滞回环面积越大. H13 钢在实验中呈现循环软化的特征，应变幅越大，疲劳寿命越短，1.1% 应变幅试样 寿命约为 0.7% 应变幅试样的 61.2%. 应变幅的增加对裂纹萌生和扩展起促进作用，1.1% 应变幅试样裂纹扩展最明显. 高温 非真空实验条件下，材料表面产生的氧化物也会促进裂纹扩展. 疲劳后试样微观组织发生明显的长大和粗化，较大应变幅对 碳化物析出有更大的助力，还会加速材料软化. 有应变幅试样显微硬度远低于无应变幅试样. 关键词    H13 热作模具钢；等温疲劳；疲劳行为；应变；碳化物 分类号    TG142.1 Effect of strain amplitude on the isothermal fatigue behavior of H13 hot work die steel ZHU Zhen-qiang，NING Hui，ZUO Peng-peng，WU Xiao-chun苣 School of Material Science and Engineering, University of Shanghai, Shanghai 200444, China 苣 Corresponding author, E-mail: wuxiaochun@shu.edu.cn ABSTRACT    Thermal  fatigue  cracking  is  the  main  failure  mode  of  hot  work  die  steel  during  die  casting  and  hot  forging.  Thermal fatigue cracking accounts for a large proportion of mold failures and seriously affects the service life of the mold. Because of the high maintenance and replacement costs, thermal fatigue failure will cause substantial financial losses to the enterprise. Therefore, analyzing the fatigue behavior of hot work die steel at high temperatures is of significance in scientific research and engineering applications. H13 hot work die steel is widely used in die casting and hot forging because of its excellent high-temperature performance and toughness. In this study,  a  600   ℃ isothermal  fatigue  test  was  conducted  on  H13  hot  work  die  steel  samples.  The  effect  of  three  different  strain amplitudes  of  0.7%,  0.9%,  and  1.1% on  the  isothermal  fatigue  behavior  was  analyzed  using  a  micro  Vickers  hardness  tester, metallographic  microscope,  microscope  with  a  superwide  depth  of  field,  and  scanning  electron  microscope.  Results  show  that  the stress–strain hysteresis loop is symmetric. The larger the strain amplitude is, the larger the area of the hysteresis loop. H13 hot work die steel exhibits the cyclic softening behavior during the experiment. The larger the strain amplitude, shorter is the fatigue life. The fatigue life of the sample with the strain amplitude of 1.1% is approximately 61.2% of that of the sample with the strain amplitude of 0.7%. The increase in the strain amplitude promotes the initiation and propagation of cracks, and the propagation of cracks on the sample with the strain amplitude of 1.1% is the most obvious. Under high-temperature and non-vacuum experimental conditions, oxide on the surface of the material promotes crack growth. The microstructure of the sample under isothermal fatigue grows and coarsens. The large strain amplitude not only supports carbide precipitation but also accelerates cyclic softening of the material. The microhardness of samples with strain amplitude is lower than that of samples without strain amplitude. 收稿日期: 2020−04−01 基金项目: 国家重点研发计划资助项目（2016YFB0300400, 2016YFB0300404） 工程科学学报，第 43 卷，第 5 期：656−662，2021 年 5 月 Chinese Journal of Engineering, Vol. 43, No. 5: 656−662, May 2021 https://doi.org/10.13374/j.issn2095-9389.2020.04.01.003; http://cje.ustb.edu.cn