GH536高温合金焊接接头疲劳裂纹萌生与扩展原位试验研究

采用原位疲劳试验方法，实时观察了GH536焊接接头疲劳裂纹的萌生和扩展行为，从而揭示了GH536焊接接头疲劳裂纹的萌生和扩展机制:疲劳加载过程中，位错沿滑移带在晶界前沿塞积，晶界阻碍位错运动，裂纹沿滑移带开裂，萌生疲劳裂纹；疲劳裂纹扩展初期，受单滑移的交替作用，裂纹呈“Z”字型向前扩展，随后裂纹的扩展逐渐以主应力控制为主，垂直于加载方向、平直向前扩展；GH536合金焊接接头组织中的晶界和碳化物会阻碍疲劳裂纹的扩展。

In-situ Study of Fatigue Crack Initiation and Propagation in Welded Joint of GH536 Superalloy

Behavior of fatigue crack initiation and propagation in GH536 superalloy welded joint was real-timely observed by in-situ fatigue experiment. And the mechanism of fatigue crack initiation and propagation was analyzed. During fatigue cycle loading, dislocations move along slip bands and pile up in front of grain boundaries. Grain boundaries hinder the movement of dislocations, eventually causing slip-bands separation and transgranular fatigue crack initiation. At the beginning of crack propagation, crack tip extends in the pattern of “Z” under the alternate effect of single slip systems;and then crack tip extends perpendicularly to the loading direction under the effect of main stress. Grain boundaries and carbides hinder the extending of fatigue cracks.