微量氢对电子束焊接TA15钛合金疲劳寿命的影响

对TA15钛合金电子束焊接试样进行充氢,研究了充氢对显微组织形态的影响,并对微量氢对TA15疲劳寿命影响进行考察。显微组织研究表明:充氢量低于0.105%(质量分数)时,氢以固溶态存在于合金中,并未形成氢化物。疲劳试验结果表明:随充氢量的增加,疲劳寿命大幅下降;这是由于微量氢的存在降低了TA15合金的韧性,固溶氢增加了疲劳裂纹的扩展速率,且氢通过影响裂纹尖端的性能加速疲劳裂纹扩展。焊缝区马氏体束呈团状结晶,且以团为单位统一变形,导致断口上呈团簇形态;且氢对马氏体团疲劳扩展中的行为有一定影响。

Effect of Trace Hydrogen on the Fatigue Lives of Electron Beam Welded TA15 Titanium Alloys

The influences of hydrogen charging on microstructure and fatigue lives of electron beam welded TA15 alloys were studied. The microstructure observation shows that hydrogen exists in the alloy in the form of solid solution, and no hydride is formed when the hydrogen content is less than 0.105% (mass fraction). Fatigue life tests show that with the hydrogen content increasing, the fatigue life in the welded joints drops. It is because trace hydrogen decreases the toughness of TA15 alloy and solid-solution hydrogen increases the fatigue crack growth rate. In addition, the hydrogen atoms accelerate the fatigue crack propagation by influencing the behavior of crack tips. The existence of the "colony structures" in the fracture morphology reveals that the martensite packets perform as a unit, and hydrogen has some effects on the martensite packet during the crack propagation.