β相锻造加工工艺中固溶温度对Ti6242合金保载疲劳性能的影响

Effect of Solution Temperature inβPhase Forging Process on Dwell Fatigue Properties of Ti6242 Alloy

对Ti6242钛合金进行不同固溶温度(960,980℃)下的β相锻造加工,研究了不同固溶温度下合金的显微组织和拉伸性能,以及高峰值应力下的低周疲劳与保载疲劳性能。结果表明:不同固溶温度下β相锻造后Ti6242合金组织相似,均由网篮组织、晶内α相片层组织和羽毛状α相集束组织组成,960℃固溶温度下羽毛状α相集束多于980℃固溶温度下。与960℃固溶温度下β相锻造后相比,980℃固溶温度下β相区锻造后合金的强度较高,断后伸长率略低,低周疲劳寿命明显较低,保载疲劳敏感系数较低;980℃固溶温度下合金的保载疲劳寿命约为960℃固溶温度下的1.3倍。不同固溶温度下β相锻造后低周疲劳断口的疲劳特征明显,均由疲劳裂纹源、疲劳裂纹扩展区和瞬时断裂区组成,而保载疲劳断口均由韧窝和疲劳条带组成,呈现出一种以蠕变断裂为主、疲劳断裂为辅的断裂模式。

The Ti6242 titanium alloy was processed byβphase forging at different solution temperatures(960,980℃),and the microstructure and tensile properties of the alloys under different solution temperatures,as well as low cycle fatigue and dwell fatigue properties under high peak stresses were studied.The results show that the microstructures of Ti6242 alloy afterβphase forging at different solution temperatures were similar,and consisted of net basket structure,in-grainαlayer structure and featherαphase cluster structure.The featherαphase phase cluster at solution temperature of 960℃was more than that at solution temperature of 980℃.Compared with those byβphase forging at solution temperature of 960℃,the strength of the alloy processed byβphase forging at solution temperature of 980℃was higher,the percentage elongation after fracture was slightly lower,the low-cycle fatigue life was obviously lower,and the dwell fatigue sensitivity coefficient was lower;the dwell fatigue life at solution temperature of 980℃was about 1.3 times of that at solution temperature of 960℃.The low-cycle fatigue fracture afterβphase forging at different solution temperatures had the obvious fatigue characteristics,and consisted of fatigue crack source,fatigue crack propagation zone and transient fracture zone.The dwell fatigue fracture was composed of dimples and fatigue bands,and the fracture mode was dominated by creep fracture and supplemented by fatigue fracture.