Comparison of Cu, Ti and Ta interlayer explosively fabricated aluminum to stainless steel transition joints for cryogenic pressurized hydrogen storage

Fabrication of a bimetallic joint to facilitate a material transition from a 6061-T651 aluminum pressure vessel liner to stainless steel tubing in cryogenic pressure vessels is explored using three different dissimilar metal interlayers with an explosive welding (EXW) process. Due to difficulties in directly EXW joining aluminum (Al) 6061 to 304 stainless steel, interlayers are used to prevent interaction of the aluminum and stainless steel, thus minimizing brittle intermetallic phase formation. Titanium (Ti), copper (Cu), and tantalum (Ta) were selected as the dissimilar metal interlayer materials; each having advantages and disadvantages. Titanium is a commonly used interlayer for this joint, but can microcrack during EXW if the bonding parameters are not correct. Copper has the advantage that it is compatible with hydrogen, but is also known to form brittle intermetallics with aluminum. Tantalum is ductile and bonds well to both Al and stainless steel, and is a high temperature metal that does well to prevent interdiffusion and intermetallic phase formation. However Ta is the most expensive metal of the three. Results of the characterization of the three interlayer bonds showed that Ti produced the highest strength joints, Ta produced the most ductile joints, and Cu produced a joint that failed with low ductility at the Al/Cu interface. Based on these results, the Cu-interlayer joint is not recommended for this application, while the Ti and Ta interlayer bonds both appear to have sufficient strength and ductility for the intended use. Copyright (C) 014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.