Role of Ti3AlC2 MAX phase on characteristics of in-situ synthesized TiAl intermetallics. Part II: Phase evolution

Abstract

In this research, the 2nd part of a series of papers on the processing and characterization of TiAl–Ti3AlC2 composites, the phase evolution during the manufacturing process was investigated by X-ray diffraction (XRD) analysis and Rietveld refinement method. Metallic Ti and Al powders with different amounts of previously-synthesized Ti3AlC2 additives (10, 15, 20, 25 and 30 wt%) were ball-milled and densified by spark plasma sintering (SPS) under 40 MPa for 7 min at 900 °C. Before the sintering process, XRD test verified that the powder mixtures contained metallic Ti and Al as well as Ti3AlC2 and TiC (lateral phase synthesized with Ti3AlC2) phases. In the sintered composites, the in-situ synthesis of TiAl and Ti3Al intermetallics as well as the presence of Ti3AlC2 and the formation and Ti2AlC MAX phases were disclosed. The weight percentage of each phase in the final composition of the samples and the crystallite size of different phases were calculated by the Rietveld refinement method based on the XRD patterns. The size of Ti3AlC2 crystallites in sintered samples was compared with the crystallite size of synthesized Ti3AlC2 powder.

Role of Ti3AlC2 MAX phase on characteristics of in-situ synthesized TiAl intermetallics. Part IV: mechanical properties

“…This paper is 4 th section of series of papers that will study the mechanical characteristics of as-prepared composite samples. The densification behavior, phase evolution, and microstructure development were investigated in pervious 3 papers of these series [25][26][27].…”

“…This part is 4 th section of a series that three sections of them have recently been published. The sintering and densification behavior were discussed in the 1 st section of these series [25], the phase characterization was studied in the 2 nd section of these series [26], and the microstructure investigation was reported in the 3 th section of these series [27]. Table 1 presents the results of the measured Fig.…”

Role of SPS temperature and holding time on the properties of Ti3AlC2-doped TiAl composites

“…However, the development and application of such materials have been restricted by their shortcomings like weak formability and lowtemperature ductility [5][6][7]. Therefore, utilizing a suitable consolidation technique and reinforcement introduction or changing the composition is an appropriate approach to overcome such weaknesses [8][9][10][11]. Spark plasma sintering (SPS) as a newly developed route that uses a direct or pulsed current and external load, simultaneously, can be employed to manufacture TiAl-based composites with developed microstructure [12][13][14][15].…”

Microstructure and mechanical properties of Ti3SiC2 MAX phases sintered by hot pressing

“…The bonds within the nitride or carbide layers are very strong, while the bonds between the layers are weaker and allow for basal slip and dislocation [3]. MAX phases combine some advantages of ceramic and metal, and the ternary compounds have an abrasion-resistant layer that can be machined and do not become brittle [8][9][10]. Recently, Ti3SiC2 has been of practical interest because of its unique and excellent combination of physical and mechanical properties such as relatively low hardness (HV 4 GPa), high electrical (4.5×10 6 Ω -1 m -1 ) and thermal conductivities (40 W/m.k) which is twice that of titanium metal [11][12][13][14], excellent oxidation resistance, thermal shock resistance, high melting point (3000 °C), high damage tolerance, machinability, high stability at high temperatures, relatively low density (4.53 g/cm 3 ), high elastic modulus and strength, and a high ratio of fracture toughness to strength, also self-lubricating properties [4,[15][16][17][18][19].…”