转速对7055铝合金搅拌摩擦焊接头断裂特征的影响

采用搅拌摩擦焊对5 mm厚7055铝合金进行对接试验,通过拉伸试验研究不同转速接头断裂位置及其横截面的显微组织,断口形貌特征.结果表明,随着转速的提高,薄弱区发生了转移:当转速为700~800 r/min时,接头在热影响区发生45°剪切断裂;当转速提高至900~1 100 r/min时,接头在焊核区发生"S"形断裂;进一步提高转速至1 200~1 400 r/min时,接头沿着前进侧热力影响区或前进侧热力影响区与焊核区边界发生断裂.断口形貌分析表明,热影响区断口呈现大而深的韧窝,焊核区断口呈现小而浅的韧窝,均属韧性断裂;热力影响区边界断口呈韧-脆混合断裂特征.

Influence of rotational speed on fracture characteristics of 7055 aluminum alloy friction stir welded joints

The butt welding process of friction stir welding was used on 5 mm thick 7055 aluminum alloy. The characteristics of fracture locations, microstructures of fracture cross-section and fracture surfaces of different rotational speed were investigated by tensile test. The results shows that with the increase of rotational speed, the weak zone has shifted. When rotational speed was 700~800 r/min, The fracture occurs in the heat affected zone (HAZ) was 45°shear fracture; With the rotational speed increased from 900~1 100 r/min, the fracture morphologies on the joint cross-section which fraction occurs in the nugget zone (NZ) was "S-type" fracture. Furthermore, when the rotational speed increased from 1 200~1 400 r/min, fracture occurred in the thermo-mechanically affected zone (TMAZ) of advancing side or at the border between the TMAZ of advancing side and the nugget zone. Fracture morphology analysis shows that big and deep dimples were found in the HAZ, small and shallow dimples were found in the NZ,both of them belong to the ductile fracture of eaem. The mixed ductile brittle fracture characteristic was performed in the TMAZ boundary.