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1·The weld nugget had a dynamic recrystallized, fine isometric crystal structure.

其中，焊核为明显的再结晶等轴晶粒，晶粒明显细化；

2·Dynamic recrystallization takes place in the weld nugget zone and fine grains are achieved.

焊核区发生动态再结晶，生成细小的等轴晶粒。

3·The microstructure of the welded joints was studied by optical microscopy. It is found that the weld nugget has a dynamic recrystallization, fine isometric crystal structure.

通过对焊接接头组织的分析，发现焊核区晶粒为明显的细化再结晶等轴晶；

4·This paper investigates energy distribution of air-borne acoustic signals in time-frequency domain during aluminum alloys spot welding in order to identify weld nugget states.

研究了铝合金点焊过程中声音信号的时频域能量分布，并应用它来识别点焊的熔核状态。

5·Experiment results indicate that air-borne acoustic signals contain information about weld nugget states and can be viewed as a kind of parameters that indicate the welding quality.

点焊过程中的声音信号包含着熔核形成信息，是点焊质量监控的重要参数。

6·Aiming at the zinc residue in the weld joint nugget of DP590GA, a double-impulse welding parameter with preheating impulse is designed to further improve its mechanical properties of the weld joint.

并针对DP590GA焊点熔核中锌元素的残留现象，设计出加预热的双脉冲焊接规范，进一步改善其点焊接头的力学性能。