Elevated temperature tensile and fracture behavior of Ti-6Al-4 V alloy fabricated by wire-based laser additive manufacturing: Microstructural evolution and deformation mechanism

초록

This study investigated the room and elevated-temperature tensile properties of Ti-6Al-4 V manufactured by wire laser additive manufacturing (WLAM) under various temperature conditions (room temperature, 300 degrees C, 500 degrees C, and 700 degrees C). Rapid cooling during processing produced alpha' martensite and alpha/(3 lamellar structures with strong crystallographic texture and high misorientation. This rapid (3 -* alpha' transformation generated distinct variants and large inter-lath misorientation, producing lattice distortions. WLAM Ti-6Al-4 V exhibited a lower (3-phase area percentage (1.7%) compared with the Wrought alloy (5.4%). These microstructural differences led to higher tensile strength than Wrought material at both room temperature and elevated temperatures. Fractography revealed micro-void formation, associated with elevated local misorientation within alpha' laths and along their interfaces. At room temperature, the alpha' martensite and fine alpha/(3 lamellar structures exhibited pronounced local misorientation near grain boundaries. At 300 degrees C, 500 degrees C, and 700 degrees C, the WLAM alloy showed delayed activation of slip systems, primarily due to its alpha-lath structure. It maintained strength up to 500 degrees C owing to its pyramidalleaning SF (basal: 0.333-0.360, prismatic: 0.226-0.247, pyramidal: 0.389-0.457), and limited CRSS reduction.

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