随焊冲击碾压对LY12CZ铝合金接头组织和性能的影响

随焊冲击碾压是一种控制薄壁结构焊接应力变形、防止热裂纹的新方法.这种方法同时也改善了LY12CZ铝合金接头组织,提高了其力学性能.金相和拉伸断口SEM观察表明,随焊冲击碾压焊缝区晶粒明显细化,组织更加致密,气孔、缩松等缺陷大大减少.与常规焊接接头拉伸断口脆性和塑性断裂特征并存相比,随焊冲击碾压焊缝断口形貌呈现典型的塑性断裂的特征.随焊冲击碾压之后,接头区的硬度有了明显提高,表明接头软化区重新得到强化.而拉伸、疲劳和三点弯曲实验结果表明,随焊冲击碾压之后接头的抗拉强度、塑性及疲劳寿命等力学性能也都得到不同程度的提高.由于薄弱的焊趾部位得到强化,裂纹萌生位置也由焊趾转移到焊缝.

Influence on Metallographic Structure and Mechanical Properties of LY12CZ Welded Jointed with Weld with Trailing Impactive Rolling

Weld with trailing impactive rolling (WTIR) is a new technique to reduce the residual stress and distortion and prevent hot cracking of thin-walled structure.WTIR can ameliorate the metallographic structure and improve the mechanical property of the LY12CZ aluminum alloy.Metallograph and SEM observation of the tensile fracture show that the crystal grain of the WTIR weld is finer and the metallurgical structure is more compact than that of the ordinary weld.There are less gas cavity and shrinkage porosity in the WTIR weld.The fracture of ordinary weld has the brittle and plastic character; however, that of the WTIR weld is a typical plastic fracture.The hardness of the welded joint of WTIR is higher than the routine welded joint, which means the softened zone of the weld is strengthened by the WTIR.The experimental results of tensile, fatigue and three point bending test show that the tensile strength, plasticity and fatigue life are improved simultaneously.The crack started from the center of the weld of the WTIR rather than the weld toe of the ordinary weld,so the general weak weld toe is intensified by WTIR.