Abstract
Abstract Microstructural evolution and interfacial reactions during active metal vacuum brazing of Ti (grade-2) and stainless steel (SS 304L) using a Ag-based alloy containing Cu, Ti, and Al was investigated. A Ni-depleted solid solution layer and a discontinuous layer of (Ni,Fe)2TiAl intermetallic compound formed on the SS surface and adjacent to the SS-braze alloy interface, respectively. Three parallel contiguous layers of intermetallic compounds, CuTi, AgTi, and (Ag,Cu)Ti2, formed at the Ti-braze alloy interface. The diffusion path for the reaction at this interface was established. Transmission electron microscopy revealed formation of nanocrystals of Ag-Cu alloy of size ranging between 20 and 30 nm in the unreacted braze alloy layer. The interdiffusion zone of β-Ti(Ag,Cu) solid solution, formed on the Ti side of the joint, showed eutectoid decomposition to lamellar colonies of α-Ti and internally twinned (Cu,Ag)Ti2 intermetallic phase, with an orientation relationship between the two. Bend tests indicated that the failure in the joints occurred by formation and propagation of the crack mostly along the Ti-braze alloy interface, through the (Ag,Cu)Ti2 phase layer.
Highlights
TITANIUM is the material of natural choice in various industrial applications due to its unique combination of specific strength and excellent corrosion resistance
These test results showed that small sized defects such as porosity or lack of fusion were not present at the stainless steel (SS)-Ti interface
Pure grade-2 Ti was successfully brazed to SS 304L using Silver-ABA alloy at 1203 K (930 °C), and the following conclusions were drawn from the study
Summary
TITANIUM is the material of natural choice in various industrial applications due to its unique combination of specific strength and excellent corrosion resistance. The extensive use of Ti and its alloys in various sectors, for example, aerospace, transportation, chemical, nuclear, and power generation, requires them to be joinied to other materials for integration and fabrication of various components.[1,2] Of particular interest to the nuclear industry, is the application of Ti in fabricating the dissolvers of spent nuclear fuel used in reprocessing plants. In spite of such vital applications, success in producing reliable and strong Ti-SS joints has been limited, primarily due to the lack of metallurgical compatibility that leads to the formation of brittle intermetallic compounds between these materials.[4,5,6,7]
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