镍基粉末冶金FGH95高温合金的拉伸及低周疲劳性能研究

在420～650℃的温度范围内,研究了PM FGH95高温合金在应变率0.0001～0.01 s-1范围内的拉伸性能及在不同应力比R=-1及R=0下的低周疲劳性能.拉伸试验结果表明:在此温度范围内,应变率对弹性模量、拉伸屈服强度及塑性模量的影响可以忽略不计;并且应变率自0.0001 s-1增大至0.01 s-1时,弹性模量、拉伸屈服强度及塑性模量受温度的影响也不明显.PM FGH95合金受材料微结构的影响很大,材料含有的微缺陷对其力学性能有非常不利的影响.LCF试验结果表明:PM FGH95合金是循环硬化材料.当应力比R=-1时,温度对LCF寿命的影响很小;但在应力比R=0时,LCF寿命受温度的影响很大,且随着温度的增加材料的低周疲劳寿命减小.SEM断口扫描发现,断裂表面有很多的解理面,但没有疲劳条带,且此断裂模式下没有明显的塑性变形,所以FGH95合金的低周疲劳寿命几乎是由裂纹萌生阶段决定的.

Tensile and Low Cycle Fatigue Properties of Nickel base Powder Metallurgy Superalloy FGH95

The tensile behavior of a nickel-base powder metallurgy(PM)FGH95 superalloy was studied in the temperature range from 420℃ to 650℃ with strain rate from 0.0001 s-1 to 0.01 s-1.The low cycle fatigue(LCF)behavior of this superalloy was investigated in the temperature range from 420℃ to 650℃ under push-pull mode(R=-1)and pull mode (R=0)at strain rate of 0.001 S-1.The results of tensile testing show that the effect of strain rate on the Young's modulus,tensile yield strength,and plastic modulus can be neglected in the experimental temperature range.And the influence of temperature on the Young's modulus,tensile yield strength,and plastic modulus is not obvious in the strain rate range from 0.000 1 s-1 to O.01 s-1.The PM FGH95 is sensitive to the micro-defect.which has a significant deleterious effect on FGH95 material mechanical behavior.The results of LCF reveal that the PM FGH95 is the cyclic hardening material.For mode R=-1.the effect of temperature on LCF life can be neglected;but for mode R=0,the temperature has profound influence on the LCF life.At this case,the LCF life decreases drastically with the temperature increasing.The SEM investigation of LCF specimens shows that there are a lot of cleavages on fracture surface,fatigue striations are absent,and this fracture mode may not involve significant plastic deformation.So the LCF life of PM FGH95 is almost determined by the crack initiation stage.