Microstructure evolution mechanism and mechanical properties of TC11-TC17 dual alloy after annealing treatment

In this paper, TC11-TC17 dual alloy specimens were fabricated by wire and arc additive manufacturing (WAAM) technique with wrought TC17 as substrate, TC11 wire as feedstock. Annealing treatments were performed at 560 degrees C,700 degrees C and 800 degrees C in vacuum for 2 h followed by air cooling in order to optimize the microstructure and mechanical properties of TC11-TC17 specimen in as-built condition. The effect of heat treatment on the specimens was investigated. Results showed that the undesirable martensite alpha' in the top region, which will degrade the mechanical response of the specimen, was eliminated after 560 degrees C annealing treatment. When the specimen was heated to 700 degrees C and 800 degrees C, the specially alternately arrayed morphology of coarse a phase and fine alpha phase in the bottom region was gradually transformed into uniform microstructure morphology. More homogeneous microstructure can also be observed in the TC17 substrate after 800 degrees C, both in HAZ and base metal. The micro-hardness value presented to be more uniform in TC17 substrate around 349.6 HV0.2 after 800 degrees C. It is believed that these changes will enhance the ductility of TC11-TC17 specimen. Tensile tests showed the elongation was improved from 9.7% to 10.5% (700 degrees C) and 12.3% (800 degrees C) with acceptable strength loss. (C) 2020 Elsevier B.V. All rights reserved.