Fabrication Of TiB Research Articles

Fabrication of TiB2/Al composite by melt-SHS process with different content of titanium powder

Abstract

Fabrication of TiB2 nanoparticulates-reinforced aluminum matrix composites by powder metallurgy route

Al/TiB2 nanocomposites were fabricated via powder metallurgy route through a primarily cold isostatic pressing of aluminum powder containing 1.5, 2.5, 3.5, 5, and 10 Vol.% of TiB2 nanoparticles and subsequent sintering at two temperatures of 650℃ and 680℃. Density, phase analysis, microstructure, and compressive strength of the samples were then characterized. Results indicated that with increasing the content of the second phase (TiB2), the amount of structural deteriorations like porosity and crack increases as a result of poorer distribution of ceramic nanoparticles, agglomeration, and retarded sintering. However, the compressive strength of nanocomposites tends to enhance with addition and increasing the amount of reinforcement phase (TiB2). Improvement in the compressive strength of composites is a result of activation of strengthening mechanisms such as formation and pile-up of dislocations. The trend of the compressive strength decreases after reaching a maximum amount for Al-2.5TiB2, in 680℃. Generally, samples with moderate amounts of TiB2 (2.5–5 Vol.%) have shown better microstructural and mechanical characteristics due to efficient impact of strengthening mechanisms with lower negative effects of destructive factors like porosity and agglomeration.

Fabrication of TiB<sub>2</sub>-TiC Composites Optimized by Different Amount of Carbon in the Initial Ti-B-C Powder Mixture

Composites of TiC and TiB2 (TiC-TiB2) were prepared by self-propagating high-temperature synthesis (SHS), using compacted reactant different combinations of Ti, C, and B powders. It is very difficult to densify these materials using conventional sintering techniques. It was found that the chemical reaction between the starting Titanium, boron and carbon particles could be completed at 1200°C producing a pure TiB2+TiC ceramic composite. Various carbon content causes the microstructure of the final products was different.

Fabrication of TiB<SUB>2</SUB>/TiC Composites by Spark Plasma Sintering

采用金属钛粉和碳化硼为初始粉料, 利用SPS放电等离子烧结技术制备了致密的纳米结构TiB 2 /TiC复合材料. 并借助XRD、SEM考察了复合材料的相组成和显微结构, 利用压痕法和小样品力学性能测试方法(MSP)测定了室温显微硬度、断裂韧性和MSP强度. 研究结果表明: 利用一步法直接升温至1550℃并保温6 min制备的复合材料, 其晶粒尺寸大于1 μm, MSP强度为833 MPa. 而采用两步法升温至1550℃, 然后迅速降低保温温度至1450℃, 并保温6 min条件下使金属钛粉和碳化硼同步完成反应、烧结、致密化, 生成晶粒细小的TiB 2 /TiC复合材料, 晶粒尺寸大约为200 nm, 并且所制备的复合材料力学性能更好, MSP强度达到1095 MPa.

Fabrication of TiB<SUB>2</SUB>–FeAl Cermet by Mechanical Milling and Subsequent Pulsed Current Sintering

A TiB2-FeAl cermet was successfully fabricated by the mechanical milling of TiB2, Fe and Al powders, and subsequent pulsed current sintering. A FeAl phase was formed during the sintering process by the diffusive reaction of Fe and Al. The transverse rupture strength of the sintered sample depends on the milling condition. A suitable condition in this process was the revolution speed of 180 rpm and the milling time for 18 ks. The TiB2-40 mass% FeAl prepared from the powder milled by this condition shows a transverse rupture strength of 1370 MPa and a hardness of 86 HRA.

Fabrication of TiB<SUB>2</SUB>–Fe–Al Cermet Alloys Synthesized by Pulsed Current Process

Mechanical alloying and pulsed-current sintering were used to synthesize TiB 2 -Fe-Al cermet alloys consisting of titanium boride and iron aluminide intermetallic compound. A mixture was obtained to which Fe was minutely distributed by mechanically alloying TiB 2 powder and Fe powder for 180ks. Mixture powders of TiB 2 -20mass%Fe3Al and of TiB 2 -24 mass%FeAl were prepared by mixing an Al powder with this mechanically alloyed powder using a mortar. The added Al reacted with Fe after it had melted when these mixtures were heated. These powders were sintered for a short time and at low temperature using pulsed-current sintering process, but these sintered compacts had pores. Several iron aluminide intermetallic compounds were generated in the TiB 2 -20mass%Fe 3 Al. Therefore, the TiB 2 -20mass%Fe 3 Al compact was hard and brittle. However, the TiB 2 -24 mass%FeAl sintered body was composed only of TiB 2 and FeAl, and had better ductility. A slight weight increase resulted from oxidation even though it was heated to 800 K or more in the air, but both sintered compacts retained their pores.

Fabrication of TiB 2 particulate reinforced magnesium matrix composites by powder metallurgy

Magnesium metal matrix composites (MMCs) reinforced with 10, 20 and 30 vol.% TiB 2 particulates, respectively, were fabricated by powder metallurgy. The microstructure, porosity, hardness and abrasive wear behavior of the composites were evaluated. Microstructural characterization of Mg MMCs showed generally uniform reinforcement distribution. As compared with pure Mg, the hardness (HB) values of Mg MMCs reinforced with 10, 20 and 30 vol.% TiB 2 particulates were increased by 41%, 106% and 181%, respectively. The abrasive wear tests showed that the wear resistance of Mg MMCs is increased with the increasing of the reinforcement volume fraction. This was due to the strong particulate-matrix bonding and high hardness of the TiB 2 particulate.

Fabrication of TiB 2 reinforced Al 3Ti composite layer on Ti substrate by reactive-pulsed electric current sintering

A TiB 2 reinforced intermetallic compound Al 3Ti composite coating layer was formed by reactive-pulsed electric current sintering of mechanically alloyed Al–Ti–B or Al–Ti–TiB 2 powders, and was simultaneously bonded to a Ti substrate to improve its wear and oxidation properties. The sintering behavior was investigated to obtain a fully dense and homogeneous Al 3Ti/TiB 2 coating. Bonding to substrate was achieved by the formation of reaction layers at the bonding interface and the reaction kinetics were investigated. Although the wear properties of monolithic Al 3Ti coating could be improved by the reinforcement of TiB 2, the oxidation properties at high temperature (1273 K) were degraded due to the decomposition of TiB 2 to elemental Ti and B.

Fabrication of TiB<SUB>2</SUB>/Al Composites by Combustion Synthesis of Al-Ti-B System

Aluminum matrix composites reinforced with TiB 2 particles which were synthesized in situ by a combustion reaction between titanium and boron were fabricated from powder mixtures of Al, Ti and B. The combustion reaction was generated in the compacted powder mixtures with and without preheating by an ignitor. The influences of a powder mixing ratio, porosity and preheating of the compacted reactant on the combustion reaction for the Al-Ti-B system were experimentally investigated. The aluminum matrix composites including 30 to 60 vol%TiB 2 could be fabricated by the combustion reaction without preheating, but some macroscopic cracks were occurred in the composites except for the Al-50 vol%TiB 2 . The relatively large porosity and preheating before the combustion reaction were effective to the self-propagation of the combustion reaction and microstructure of the synthesized composites, especially in the low volume fraction of TiB 2 . The reaction between titanium and boron in the Al-Ti-B system was initiated after the melting of aluminum.

Fabrication of TiB2 and TiB2/FeB composites by mechanically activated borothermic reduction of ilmenite

TiB2 and TiB2/FeB composites have been formed at temperatures below 1000 °C, directly from ilmenite sand by reaction with amorphous boron. The structural transformations occurring during high-energy mechanical milling pretreatment and subsequent annealing of different mixtures of the constituents have been studied. On heating at temperature below 800 °C, complete borothermic reduction of the ilmenite structure is accomplished. The mixture so obtained with an ilmenite-boron ratio equal to 1/6 undergoes a sequence of reactions on further heating to form TiB2, FeB, and the amorphous phase B2O2.