Synthesized Titanium Matrix Composites Research Articles

Microstructure effect on mechanical properties of in situ synthesized titanium matrix composites reinforced with TiB and La 2O 3

High temperature titanium matrix composites (TMCs) with different volume fraction of reinforcements were in situ synthesized by casting and hot forging. An effort was made to investigate the mechanical properties as a function of the microstructure of composites. Tensile tests were performed at room temperature, 600 °C, 650 °C and 700 °C respectively. Creep behavior at 650 °C was characterized in the stress range of 200–300 MPa. Results indicated that the composite with 2.11 vol.% reinforcements had the highest tensile strength and lowest steady state creep rate. Morphology of TiB whiskers was critical to mechanical properties of TMCs. TiB whiskers fracture and debonding acted as the dominant failure modes.

Effect of reinforcements on high temperature mechanical properties of in situ synthesized titanium matrix composites

Four types of high temperature titanium matrix composite reinforced with multi-dimensional reinforcements are synthesized by common casting and hot-forging technology utilizing the reaction between Ti and LaB 6, B 4C. The microstructure and tensile properties at elevated temperature of the composites are characterized and tested. The strengthening mechanism of composites can be summarized as two main reasons: the load bearing effect of TiB short fibers and dispersion strengthening effect of TiC/La 2O 3 particles. The effect of TiB short fibers on high temperature strength is quite different from room temperature. The composite with the lowest volume fraction of reinforcements shows the best high temperature mechanical properties due to the efficient strengthening of TiB whiskers in the whole high temperature range.

Evaluation of Interfacial Reaction between Titanium Matrix Composites and Aluminium Alloy

The main purpose of this study is to evaluate the interfacial reaction between titanium matrix composites (TMCs) and A380 alloy in aluminum die-casting. In-situ synthesized titanium matrix composites and H13 tool steel were immersed in molten A380 alloy in a mold at 993 K for times varying from 0 to 1200 s. In-situ synthesis TMCs and interfacial reaction between TMCs and A380 alloy were examined by X-ray diffraction, optical microscope, scanning electron microscope and electron probe micro-analyzer. The reaction behavior shows that TMCs can a substitution for H13 tool steel.

Microstructural characterization of Y 2O 3 in in situ synthesized titanium matrix composites

Titanium matrix composites reinforced with TiB, TiC and Y 2O 3 are fabricated by a non-consumable arc-melting technology utilizing chemical reaction between titanium, B 2O 3, B 4C and Y. Microstructure of in situ synthesized Y 2O 3 was observed by scanning electron microscope (SEM), transmission electron microscope (TEM) and high-resolution transmission electron microscope (HREM). The Y 2O 3 forms in a way of nucleation and growth. Primary Y 2O 3 tends to grow in dendritic shape and becomes coarse. Secondary Y 2O 3 mostly grows in sphericity and the size is very small. Moreover, there is no fault in the Y 2O 3 reinforcements. The interface between Y 2O 3 and titanium was observed by means of TEM and HREM. Three groups of crystallographic relationships between Y 2O 3 and Ti were found. The interface between the Y 2O 3 and the titanium matrix is very clean and well bonded, and there is no interfacial reaction.

In situ technique for synthesizing multiple ceramic particulates reinforced titanium matrix composites (TiB + TiC + Y 2O 3)/Ti

In situ synthesized titanium matrix composites reinforced with multiple ceramic particulates including TiB, TiC and Y 2O 3 were fabricated by non-consumable arc-melting technique utilizing the chemical reaction among Ti, B 2O 3, B 4C and Y. The thermodynamic feasibility of the in situ reactions has been considered. X-ray diffraction (XRD) was used to identify the phases in the composites. Microstructures of the composites were observed by means of optical microscope (OM), scanning electron microscope (SEM) and electron probe. It is concluded that multiple reinforcements are synthesized and they show different shapes: TiB grows in needle shape; TiC grows in near-equiaxed and rod-like shapes; Y 2O 3 grows in near-equiaxed shapes when the content of Y is 0.6 wt.% and grows in dendritic shapes when the content of Y increases to 1.8 wt.%. Reinforcements TiB, TiC and Y 2O 3 are distributed uniformly in the titanium matrix.

Net-Shaping of <I>In-situ</I> Synthesized (TiC+TiB) Hybrid Titanium Matrix Composites

The aim of this study is to establish an effective technique for the economic net-shape forming of in-situ synthesized titanium matrix composites (TMCs) using a casting route. In-situ synthesis and investment casting of TMCs were carried out in a horizontal centrifugal vacuum induction melting furnace. The synthesized (TiC+TiB) TMCs were examined using scanning electron microscopy, electron probe microanalyzer and X-ray diffraction, and through thermodynamic calculations. No melts-mold reaction was observed between the synthesized composites and a SKK mold, since the SKK mold comprised both interstitial and substitutional melts-mold reaction products. The results of the in-situ synthesis and the investment casting of TMCs show that our casting route can be an effective approach for the economic net-shape forming of TMCs.

The orientation relationship between TiB and RE 2O 3 in in situ synthesized titanium matrix composites

In the present work, the orientation relationship between TiB and RE 2O 3 in (TiB + RE 2O 3)/Ti composites were observed. The orientation relationships of TiB and Nd 2O 3 can be described as: [ 0 1 1 ] TiB / / [ 0 2 1 ] N d 2 O 3 ; [ 0 1 1 ¯ ] TiB / / [ 1 ¯ 0 0 ] N d 2 O 3 . The orientation relationships of TiB and Y 2O 3 can be described as: [ 1 ¯ 0 1 ] TiB / / [ 0 2 1 ] Y 2 O 3 ; ( 1 1 1 ) TiB / / ( 1 2 ¯ 1 ) Y 2 O 3 , furthermore. The formation of orientation relationship between TiB and RE 2O 3 is related to the solidification process of the composites.

Tensile properties of in situ synthesized titanium matrix composites reinforced by TiB and Nd2O3 at elevated temperature

Titanium matrix composites reinforced with TiB and Nd2O3 were prepared by a non-consumable arc-melting technology. X-ray diffraction (XRD) was used to identify the phases in the composites. Microstructures of the composites were observed by means of optical microscope (OM). There are three phases: TiB, Nd2O3 and titanium matrix. TiB grows in needle shape, whereas Nd2O3 grows in lath shape. Tensile properties of the composites were tested at 773, 823 and 873 K. Both the fracture surfaces and longitudinal sections of the fractured tensile specimens were comprehensively examined by scanning electron microscope (SEM). The fracture mode and fracture process at different temperatures were analyzed and explained. It shows that the tensile strength of the composites has a significant improvement at elevated temperatures compared to titanium matrix. The ductility of the composites improves with the content of neodymium and the test temperatures. The titanium composite exhibits different fracture modes at different test temperatures.

Mechanical Properties of <I>in situ</I> Synthesized Titanium Matrix Composites at Elevated Temperature

TiB and TiC reinforced titanium matrix composites were produced by common casting technique utilizing the self-propagation hightemperature synthesis between titanium and B4C. The mechanical properties and fracture mechanism of in situ synthesized titanium matrix composites have been investigated by means of uniaxial tension at elevated temperatures. As temperature increases, the ultimate tensile strength decreases and ductility increases. Compared with the matrix alloy, ultimate tensile strength of the composite was improved obviously because the in situ synthesized reinforcements are very stable at elevated temperatures and can strengthen the matrix alloy effectively. The fracture behavior was dependent on temperature. The composites fail at low strain at room temperature due to the fracture of the reinforcements. As temperature increases, voids are likely to initiate and grow at the interface between the reinforcement and the matrix alloy, and their coalescence eventually leads to the fracture of the composites. The debonding between the reinforcements and the matrix alloy becomes the main reason for the composites failure.

Solidification paths and reinforcement morphologies in melt-processed (TiB + TiC)/Ti In Situ Composites

A novel in situ process was developed to produce titanium matrix composites reinforced with TiB and TiC of different mole ratios in which traditional ingot metallurgy plus self-propagation hightemperature synthesis (SHS) reactions between Ti and B4C, graphite powder were used. Microstructures of (TiB+TiC)/Ti in situ composites were comprehensively characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Solidification paths were investigated using a differential scanning calorimeter (DSC). Results show that there is an apparent difference in morphologies of reinforcements. The reinforcements nucleate and grow from the melt in a way of dissolution precipitation. The different morphologies are related to their solidification paths and the particular crystal structure of the reinforcement. TiB grows along the [010] direction and forms short-fiber shape due to its B27 structure, whereas TiC with NaCl type structure grows in a dendritic, equiaxed, or near-equiaxed shape. The DSC results and analysis of the phase diagram yield three stages for the solidification paths of in situ synthesized titanium matrix composites: (1) primary phase, (2) monovariant binary eutectic, and (3) invariant ternary eutectic. The addition of graphite adjusts the solidification paths and forms more dendritic primary TiC. The addition of aluminum does not change the solidification paths. However, the reinforcements grow finer and lead to equiaxed or near-equiaxed TiC morphologies. The following consistent crystallographic relationships between TiB and titanium were observed by HRTEM, i.e., [010]TiB//[ $$01\bar 10$$ ]Ti, (100)TiB//( $$\bar 2110$$ )Ti, (001)TiB//(0002)Ti, ( $$10\bar 1$$ )TiB//( $$4\overline {22} 1$$ )Ti and [001]TiB//[ $$01\bar 10$$ ]Ti, ( $$0\bar 10$$ )TiB//( $$\bar 2110$$ )Ti, (200)TiB//(0002)Ti. The formation of the preceding crystallographic relationships is related to the growth mechanism of TiB. It also helps to minimize the lattice strain at the interfaces between TiB and the titanium matrix.

Microstructural characterization of TiB in in situ synthesized titanium matrix composites prepared by common casting technique

Titanium matrix composites reinforced with TiB and TiC were fabricated by a non-consumable arc-melting technology utilizing self-propagation high-temperature synthesis reaction between titanium and B 4C. Microstructural characterization of in situ synthesized TiB was observed by scanning electron microscope (SEM), transmission electron microscope (TEM) and high-resolution transmission electron microscope (HREM). The TiB shows a typical whisker shape and the crystallographic planes of the TiB at transverse cross-section are always of the planes (100), (101) and (10 1 ̄ ). Stacking faults are observed in the TiB. The TiB forms in a way of nucleation and growth. The growth morphologies and formation of the stacking faults are related to crystal structure of the TiB. Due to its B27 structure, the TiB is likely to grow along [010] direction and form the whisker shape. The stacking faults are also likely to form in the (100) plane. The formation of above morphologies and the stacking faults serves to minimize the lattice strain at the interface between the TiB and the titanium matrix alloy.

Microstructural characterization of TiC in in situ synthesized titanium matrix composites prepared by common casting technique

TiC reinforced titanium matrix composites were produced by non-consumable arc-melting technology utilizing the self-propagation high-temperature synthesis (SHS) reaction between titanium and graphite. X-Ray diffraction (XRD) was used to identify the phases in the composites. Microstructures of the composites were observed by optical microscope (OM) and transmission electron microscope (TEM). The results show that there are two phases in the composites: TiC and titanium matrix alloy. TiC has two different shapes: dendritic shape, equiaxed or near-equiaxed shape. The in situ synthesized TiC grows by dissolution–precipitation. Analysis of the binary phase diagram determined that the solidification path undertook the following three stages: primary TiC, binary eutectic β-Ti+TiC and solid transformation. Primary TiC grows in dendritic shape due to the formation of composition undercooling. Binary eutectic TiC grows in equiaxed or near-equiaxed shape. A small quantity of TiC may form twin structure during nucleation and growth. The twin plane is the (111) plane.