Investigation of the structure and properties of hypereutectic Ti-based bulk alloys
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S4.3.1
Investigation of the structure and properties of hypereutectic Ti-based bulk alloys Dmitri V. Louzguine-Luzgin1,∗, Larissa V. Louzguina-Luzgina2,& and Akihisa Inoue1 1
Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 9808577, Japan 2 Research and Development Project, CREST, Japan Science and Technology Agency, Sendai 985-8577, Japan Keywords: Ti-based alloys, mechanical properties, intermetallic compound, high strength, ductility. ABSTRACT Structure and mechanical properties of binary Ti-TM (TM-other transition metals) and ternary Ti-Fe-(TM, B or Si) alloys produced in the shape of the arc-melted ingots of about 25 mm diameter and 10 mm height are studied. The formation of high-strength and ductile hypereutectic alloys was achieved in the Ti-Fe, Ti-Fe-Cu and Ti-Fe-B systems. The 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 Pm 3 m 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 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. INTRODUCTION The ultimate tensile strength of typical structural Ti-based alloys somewhat exceeds 1000_MPa [1]. At the same time, a special squeeze casting technique [2] allows to produce bulk glassy alloys [3,4] with high ultimate tensile strength which attains 2200 MPa for the Ti50Ni20Cu23Sn7 bulk glassy alloy [5] (alloy’s compositions are given in nominal atomic percents) and 2480 MPa for the Ti45Cu25Ni15Sn3Be7Zr5 one [6]. Ti alloys have relatively high corrosion resistance at room temperature [7]. The relatively low density of the main alloying element Ti (4.5 Mg/m3) implies a higher strength/density ratio compared to Fe- or Zr-based bulk glassy alloys. However, small critical diameter of 5-8 mm for the Ti-based bulk glassy alloys [4,6,8,9] attained so far and low ductility restrict their applications. Only addition of a toxic element Be helps to improve slightly their compressive ductility [6]. Recently, it also has been shown that a 3 mm diameter cylindrical rod of cast Ti60Cu14Ni12Sn4Nb10 alloy consisting of a micron–size β-Ti dendrites exhibit high ultimate compressive strength of 2.4 GPa and 14.5 % plastic strain [10]. The deformation behavior of the ∗ &
Louzguine is official French spelling. English spelling is Luzgin. Louzguina is official French spelling. English spelling is Luzgina.
S4.3.2
nanostructured Ti-Cu-Ni-Sn-(Ta,Nb) alloys has been studied recent
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