Ultra-strong and ductile hypereutectic Ti-based bulk alloys

摘要

The present work is devoted to the study of a number of binary Ti-TM (TM-other transition metals) and ternary Ti-Fe-(TM, Al, B or Si) as well as Ti-Fe-RE (RE-rare-earth) alloys and reports on the formation of high-strength and ductile hypereutectic Ti-Fe, Ti-Fe-Cu and Ti-Fe-Nd alloys in the form of arc-melted ingots about 25 mm diameter and 10 mm height. Structures of the high-strength and ductile hypereutectic alloys studied by X-ray diffractometry and scanning electron microscopy were found to consist of the primary cubic Pm 3 m intermetallic compound (TiFe-phase or a solid solution on its base) and a dispersed eutectic consisting of this Pm3m intermetallic compound + BCC Im 3 m β-Ti supersaturated solid solution phase. The hypereutectic Ti-Fe alloy showed excellent compressive mechanical properties. The addition of Cu and Nd improves its ductility. B addition increased mechanical strength. Ni, Cr and Mn additions caused embrittlement owing to the formation of alternative intermetallic compounds. The deformation behaviour and the fractography of the Ti-based alloys were studied in details. The reasons for the high strength and good ductility of the hypereutectic alloys are discussed.