Abstract

Precipitation hardening and corrosion behavior of a friction stir welding (FSW) based on the aluminum alloy A6005 reinforced with TiB₂ nanoparticles have been studied. Mechanical alloying (MA) and hot extrusion techniques have been employed as processing route followed by FSW. Samples characterization has been performed by DSC and TEM, and precipitation strengthening of the bulk samples and the FSW joint has been evaluated by micro-hardness tests after T6 thermal treatment. TEM characterization revealed the presence of Mg–Si hardening phases, mainly of β′ phase, and dispersoids of α-Al(FeMnCr)Si into the aluminum matrix. The results revealed that samples subjected to MA had less susceptibility to T6 thermal treatment and that the presence of nano-TiB₂ reinforcement accelerates aging time. In addition, electrochemical tests based on polarization tests have been performed in 3.5% NaCl solution to assess the effect of FSW process on corrosion behavior. The FSW joint had worse corrosion behavior since the passive Al₂O₃ film was not generated on the weld zone. SEM–EDS analysis revealed that pits nucleated mainly in sites with a higher presence of Fe contaminant which acts cathodically with respect to the aluminum matrix, producing galvanic corrosion.

Graphic Abstract

摘要

研究了用TiB ₂纳米颗粒增强的铝合金A6005搅拌摩擦焊（FSW）的沉淀硬化和腐蚀行为。机械合金化（MA）和热挤压技术已被用作FSW的加工路线。通过DSC和TEM进行了样品表征，对大块样品和FSW接头的沉淀强化已通过T6热处理后的显微硬度测试进行了评估。TEM表征表明存在Mg-Si硬化相（主要为β'相）和α-Al（FeMnCr）Si分散体进入铝基体。结果表明，经过MA处理的样品对T6热处理的敏感性较低，并且存在纳米TiB ₂增强可加速老化时间。另外，基于极化试验的电化学试验已经在3.5％NaCl溶液中进行，以评估FSW工艺对腐蚀行为的影响。FSW接头的腐蚀行为较差，因为在焊接区未生成钝化Al ₂ O ₃膜。SEM-EDS分析表明，凹坑主要在存在较高Fe杂质的位置成核，而Fe杂质对铝基体起阴极作用，产生电腐蚀。

图形摘要