Fatigue properties of titanium-clad bimetallic steel butt-welded joints

Titanium-clad (TC) bimetallic steel is a high-performance constructional material that yields promising application potential in future ocean and coastal civil engineering. However, the understanding on the mechanical behaviors of the corresponding weld joints is still limited. In this paper, a tensile-tensile fatigue experimental study was conducted on two types of butt-weld joints fabricated of hot-rolled TA2 +Q355B TC bimetallic steel. Based on the test results, the fatigue stress-life curves (S-N curve) of the two types of weld joints were obtained and subsequently compared with that of TC parent materials, other representative structural metals, that of buttweld on other metals and the codified S-N curves provided by six structural/fatigue design standards. Most specimens of the two types of TC weld joints are initially cracked at the clad-to-cap weld. The bonding strength between clad and substrate layers exhibit a promising reliability under fatigue loadings. The fatigue resistance of the two types of TC weld joints is considerably less than the different TC parent materials studied. The fatigue lives of clad material (TA2) and substrate material (Q345/Q355B) are greater than that of TC weld joints. The SN curves of two TC weld joints are considerably lower than that of high-strength steel series but higher than that of aluminum alloy 6061-T6. The design S-N curves of EC3 (Class 36) and IIW (Class 36) are too conservative for the two TC weld joints.