Analysis of local mechanical properties for welded joints of Al-Mg-Si alloys at friction stir welding

ABSTRACT

The microstructure and mechanical properties of joints made of alloy 6082-T6 obtained by friction stir welding (FST) are investigated. Welded joints have a pronounced heterogeneity in microstructure and mechanical properties. The asymmetry of the maximum temperature fields and microhardness in the zone of thermal influence (ZTI) is indicated. The joint strength of the FST average 72% of the strength of the base metal. The plasticity of welded joints is lower than the base metal by 5.3 times, because of the high deformation concentration in the minimum hardness zone. The prolonged residence of the ZTI metal in the high-temperature region leads to the dissolution process of the β” hardening particles, and, as a consequence, to a significant decrease in the hardness of the ZTI. The dependence of the alloy 6082 yield strength on hardness, which makes it possible to estimate the level of local mechanical properties in a welded joint is received.

KEYWORDS:

• Friction stir welding
• Al-Mg-Si alloy
• temperature field
• welded joint
• microstructure
• mechanical properties
• heterogeneity