Melting and solidification of TiNi alloys by cold crucible levitation method and evaluation of their characteristics

Abstract

The addition of Re, Fe and Cr into Ti-50 mol.-%Ni has been carried out to improve the oxidation and mechanical properties. The mono phase consisting of TiNi with the B2 type structure was identified in micro-alloyed materials proposed on the basis of the d-electrons concept. Experimentally, TiNi alloys were melted and solidified by the cold crucible levitation melting (CCLM) method. The TiNi-(Cr, Fe, Re) alloys with high purity and without contamination from a crucible were prepared, and the homogeneous microstructure was achieved by the diffusion mixing effect of CCLM even in the as-cast alloys which contained Re and Cr with higher melting temperatures and different specific gravities. The transformation from austenite to martensite phases occurred in all alloys below or above room temperature. Some alloys had the ability of shape memory even at room temperature. Ternary alloys showed a higher flow stress level compared with the binary TiNi alloy. On the other hand, the oxidation at 1273 K was promoted by the formation of titanium oxides (TiO 2 ) on the alloy surfaces. The oxidation resistance was improved by the formation of the continuous Cr 2 O 3 film in TiNi-Cr alloys. The alloying effects by ternary elements (Re, Fe, Cr) in the intermetallic TiNi as well as metallic materials were explained well using two parameters used in the d-electrons concept.

Alloy Design of Ti Alloys Using Ubiquitous Alloying Elements and Characteristics of Their Levitation-Melted Alloys

“…Therefore, the d-electrons concept proposed by Morinaga 7) is applied to design of titanium alloys using ubiquitous metallic elements, in order to establish the strategic method for suppressing utilization of rare metals. The high performance metallic materials such as Ni, Ti, Al, Mg and Fe-based alloys, etc [8][9][10][11][12][13] had been developed by the d-electrons concept. The properties of titanium alloys depend greatly on the exact chemical composition, processing history and smallness of undesirably dissolved elements including contaminants such as oxygen and carbon.…”

Effect of Si Addition on Microstructure and Mechanical Properties of Al–1.5%Mn Alloys

“…The d-electrons concept based on the theoretical calculation of electronic structure theory proposed by Morinaga et al 17,18) has been applied to the design of the highperformance alloys such as Al, 15,1921) Bi, 22,23) Ni 2427) and Ti, 28,29) and some physical or chemical properties of the designed alloys were successfully predicted by this concept. 15) The bond order (Bo) and the d-orbital level of the transitional alloying element (Md) have been used in this concept.…”

Uniformity analysis of magnetic field in an electromagnetic cold crucible used for directional solidification

“…EMCC presents an attractive potential for applications in preparing refractory and chemically reactive materials with little or no contamination during the melting process (Gombert and Richardson, 2003;Durand, 2005). EMCC is presently mainly used in the preparation of titanium, TiAl and TiNi alloys (Baake et al, 2003;Pericleous et al, 2006;Nakajima et al, 2000;Matsugi et al, 2008), ceramics (Hong et al, 2003), polycrystalline silicon (Ciszek, 1985;Dour et al, 1998;Gallien et al, 2011) and waste vitrification ( Jouan et al, 2002). Recently, a new EMCC technique was developed by the Harbin Institute of Technology consisting of a combination of continuous melting and directional solidification (DS) in one mould having the advantages of dual functions and high efficiency, as shown in Figure 1.…”