In Situ Synthesis of Ti5Si3 Intermetallic Particulate Locally Reinforced Medium Carbon Steel-matrix Composite via the SHS Reaction of Fe–Ti–Si System during Casting

Abstract

The in situ Ti 5 Si 3 intermetallic particulate locally reinforced steel matrix composites are successfully fabricated by the self-propagating high-temperature synthesis (SHS) reaction of Fe-Ti-Si system during casting, and the microstructures of the composites reveal a relatively uniform distribution of mango-like Ti 5 Si 3 particulates in the local reinforcing regions. XRD results reveal that in addition to a-Fe and Ti 5 Si 3 phases, the transient Fe 2 Ti is also present in the local reinforcing region of the composites. Furthermore, some Ti 3 SiC 2 particulates are formed and distribute in the limited region nearby the interface between the local reinforcing region and steel matrix. With Fe content increasing from 10 to 30 wt% in the preforms, the Ti 5 Si 3 particulate size is decreased obviously in the local reinforcing region; furthermore, the presence of significant porosity can be detected in the composite synthesized by the 10 wt% Fe-Ti-Si system; on the contrary, only a minimal porosity can be found in that synthesized by 30 wt% Fe in Fe-Ti-Si system. The macro-and micro-hardness as well as the wear resistance of the local reinforcing region are obviously higher than those of the unreinforced medium steel. Improvements in hardness and wear resistance of the composite are mainly attributed to the presence of high volume fraction of hard intermetallic Ti 5 Si 3 particulates.KEY WORDS: in situ; intermetallic; locally reinforced; steel matrix composite; SHS. Experimental ProcedureIn this study, the starting materials were made of commercial powders of 10, 20, 30, 40 and 50 wt% Fe (99.0% purity, ϳ10 mm), Ti (99.5 % purity, ϳ38 mm), and Si (99.5 % purity, ϳ15 mm), respectively. Titanium and silicon powders were used in a ratio corresponding to that of stoichiometric Ti 5 Si 3 . Powder blends with different starting compositions were dry-mixed sufficiently by a ball milling for 6 h in a cylindrical stainless steel jar containing GCr15 bearing steel balls with a ball to powder weight ratio of about 5 : 1 by mechanical rotation at 40 rpm, and then were cold-isostatically pressed into cylindrical preforms (about 20 mm diameter and 10 mm length) by using a stainless steel die with two plungers. The green preforms were pressed uniaxially at pressure ranging from 88-92 MPa to obtain relative densities of 63Ϯ2% theoretical density. Then the preforms were placed and fixed on the side of the sand mold, respectively, as schematically illustrated in Fig. 2 in Ref. 11). Subsequently, the medium carbon steel melt, which composition is measured by an ARL4460 Metals Analyzer and shown in Table 1, prepared by non-oxidation process in a 5 kg medium-frequency induction furnace with a temperature of about 1 600°C was poured into the mold to ignite the SHS reaction of the preforms. After solidification and cooling, composite castings were removed and sectioned in the side position.Vickers microhardness values of the matrix and local reinforcing region in the samples were tested under a load of 50 g with an indentarion time of 10...

Influence of reactant particle size on products of self-propagating high-temperature synthesis in 30wt.% Cr–Ti–B4C system

“…The adiabatic combustion temperature of the Cr-Ti-B 4 C system can be calculated according to the measure given by Ref. [19], and the result is that when the Cr content is 30 wt.%, the T ad can get to 2853 K. Consequently, the TiB 2 and TiC particulates are formed mainly by a solution, reaction and precipitation mechanism [15].…”

Estudio de la reactividad del titanio con partículas de adición por vía pulvimetalúrgica

“…Por otro lado, cabe destacar que en general los valores obtenidos para los parámetros tanto de dureza como de módulo elástico, han resultado superiores a los descritos en ocasiones por otros autores, tanto para la matriz de titanio (H:2-4 GPa, E:110-130 GPa) (Mante et al 1999, Hryniewicz et al 2012, Farhat et al 1997 GPa, E: 210-280GPa) (Guemmaz et al 1996, Raman et al 2012, Fang et al 2004), y el Ti 5 Si 3 (H:11,5-24 GPa, E:2,25 GPa) (Li et al 2007, Zhang, Wu 1998. Esta diferencia se atribuirá al diferente equipo de ensayo empleado, que si ha permitido en el caso de la presente investigación, distinguir entre las diferentes fases presentes para idénticas condiciones de ensayos.…”