Processing, Microstructure, and Tensile Properties of the Ti-6Al-4V- 1.55B Eutectic Alloy (Preprint)

摘要

Boron addition to conventional titanium (Ti) alloys instigates precipitation of intermetallic TiB whiskers that provide significant increases in strength and stiffness. The eutectic composition is the maximum boron concentration that provides these benefits via melt processing while maintaining reasonable ductility and damage tolerance. The eutectic point for the most widely used Ti alloy, Ti-6Al-4V (weight percent), modified by B addition, was determined to occur at 1.55+0.05B and 1545+5 degrees C. The microstructure, texture, and tensile properties of the eutectic alloy are sensitive to ingot solidification conditions and melt pool morphology. Several microstructural forms in the as-cast condition as well as their transformation during thermomechanical processing (TMP) were identified. Two types of eutectic structures, aligned and random, were obtained. Cast microstructures with random eutectic colony orientation had no marked crystallographic texture, while cast aligned microstructure had a strong 020 texture for the TiB phase and a.