Titanium-titanium boride (Ti-TiB) functionally graded materials through reaction sintering: Synthesis, microstructure, and properties

Abstract

The study demonstrates an effective method to synthesize titanium-titanium boride (Ti-TiB) functionally graded material (FGM) tiles by exploiting the simultaneous TiB whisker formation in situ and the densification occurring during the reaction sintering process. The macrostructure of the graded material was designed to have a beta-titanium (␤-Ti) layer on one side with the composite layers of Ti-TiB mixture having increasing volume fraction of the TiB through the thickness. The approach used an optimized tri-modal powder mixture consisting of ␣-Ti powder, a master alloy of the ␤-stabilizing-element powders (Fe-Mo), and TiB 2 . The structure and properties of both of these FGMs were systematically characterized by X-ray diffraction, electron microscopy, and microhardness measurements. Interestingly, it has been found that two different kinds of TiB whisker morphologies were observed in the FGMs. The Ti-rich layers were found to have large and pristine TiB whiskers uniformly distributed in the Ti matrix. On the other hand, the TiB-rich layer was found to have a network of interconnected and relatively smaller TiB whiskers appearing as clusters. The layers of intermediate TiB volume fractions were found to consist of both the morphologies of TiB. The effectiveness of the X-ray direct comparison method for the determination of volume fractions of phases in the FGM layers was also demonstrated. The Vickers microhardness level was found to increase dramatically from 420 kgf/mm 2 in the ␤-Ti layer to 1600 kgf/mm 2 in the TiB-rich layer. The elastic residual stresses retained in the graded layers after fabrication were determined based on an elastic multilayer model. The nature of microstructure, the hardness variation, and the distribution of residual stresses in these novel FGMs are discussed.

Multiscale Hierarchical Structure and Laminated Strengthening and Toughening Mechanisms

“…Han et al [17] fabricated the laminated Ti-(TiB + La 2 O 3 )/Ti composites by powder metallurgy and hot rolling process as shown in Figure 5(c), which results in an improvement of 30% in elongation compared with monolithic composites with same volume fraction of reinforcements. In 2003, Panda et al [18][19][20][21] fabricated TiB/Ti and TiB 2 /Ti functional gradient composites by powder metallurgy as shown in Figure 5(d), which effectively weakens the thermal residual stress and inhibited the formation of cracks. [12], (b) network [2], (c) laminated [17] and (d) gradient structure [18].…”

“…In 2003, Panda et al [18][19][20][21] fabricated TiB/Ti and TiB 2 /Ti functional gradient composites by powder metallurgy as shown in Figure 5(d), which effectively weakens the thermal residual stress and inhibited the formation of cracks. [12], (b) network [2], (c) laminated [17] and (d) gradient structure [18]. shown in Figure 6(b, c).…”

“…thermal stresses and delay the plastic yielding and the fracture failure of the metallic layer by the load shearing of the ceramic [18][19][20][21]. Meanwhile, it is a better overall use of the available materials by distributing them in a suitable spatial direction.…”

Fabrication, Structure, Properties and Application of Gradient Sintered Carbide-Steels with HS6-5-2 Matrix

“…The consolidation method of input materials is largely impacting the content of the structure and the character of the chemical composition change, especially in the region of layers' boundary. A liquid phase emerges very frequently when sintering multi-phase mixtures or a chemical reaction takes place [40]. Sintering with the presence of the liquid phase usually occurs at a temperature higher than the lowest melting point of one of mixture components.…”

In-Situ Fabrication of Bi/BiMn–BiMn–Mn Graded Materials by High Magnetic Field Gradients

“…These methods include powder metallurgy, centrifugal casting, laser cladding, chemical deposition, and others. [1][2][3][4] However, all these traditional techniques are relatively expensive or too complicated to be used in industrial production. Therefore, it is necessary to explore a novel method for the fabrication of FGMs.…”