Dispersion Of TiB2 Particles Research Articles

Nano-structured intermetallic compound TiAl obtained by crystallization of mechanically alloyed amorphous TiAl, and its subsequent grain growth

The amorphization process during mechanical alloying (MA) was investigated for the Al-50at%Ti and Al-50at%Ti-10vol%TiB2 powder mixtures. Pure metallic powders of Al and Ti were finely mixed and transformed to the amorphous phase after being milled for about 2880 ks. In the case of Al-50at%Ti-10vol%TiB2 powder, the amorphous alloys with a fine dispersion of TiB2 particles could be obtained for a shorter milling times than that required for the powders without TiB2 ceramics. As a result of heat treatment for the mechanically alloyed amorphous powders, a nanocrystalline intermetallic compound of TiAl (γ) could be produced. Subsequent grain growth of the γ phase during heat treatment was investigated by estimating the grain-growth exponent and the activation energy for grain growth. It was found from this estimation that the grain growth was further suppressed as the powders were mechanically alloyed for longer times. Furthermore, the addition of the TiB2 particles that could be dispersed during MA finely and homogeneously in the amorphous matrix was found to be effective for suppression of the γ grain growth especially at elevated temperatures as well as for a long annealing.

反応合成ＴｉＢ２粒子分散合金によるアルミニウムの凝固結晶粒微細化

Grain refining effects of TiB2 dispersed alloys on aluminum were investigated. The TiB2 dispersed alloys were synthesized by the reaction between titanium and AlB2, and were added to molten aluminum at 1273 K as the grain refining agents. Excess amount of titanium or aluminum was added to starting materials of the reaction for the purpose of controlling the adiabatic temperatures. In this paper, (1) distribution of TiB2 particles in molten aluminum, (2) effects of TiB2 distribution on the grain size and (3) mechanical properties of grain-refined aluminum are mainly dealt with. Since aluminum oxide forms at the inter-particle regions of TiB2, the dispersion of TiB2 particles in molten aluminum is not homogeneous when aluminum was added in the starting materials. The excess titanium addition as a diluent, however, improves the distribution of TiB2 particles. The average grain size of aluminum alloy is effectively reduced by adding the TiB2 dispersed alloy. The grain refining effects are saturated by about 0.4 vol% addition of TiB2 particles. The 0.2% proof stress of Al–2 mass%Mg alloy is improved by the grain refining.

Strengthening of Cu–Ti alloys by addition of boron

AbstractVarious Cu–Ti–B alloys were produced via argon atomisation at 1400°C. Rapidly solidified powders, containing dispersed TiB2 particles, were subsequently subjected to thermal treatment in hydrogen at temperatures between 300 and 600°C. This process resulted in the formation of fine, metastable Cu4Ti precipitates from the supersaturated solid solutions, which appreciably strengthened the copper matrix. Compared with the Cu–Ti powder particles obtained using the same procedure, the strengthening effect in Cu–Ti–B powder particles is much greater. The binary and ternary powders both reveal properties superior to those of Cu–Ti alloys produced via ingot metallurgy. This property is of interest for high conductivity electroengineering applications, since Cu–Ti–B alloys would provide a superior combination of strength and conductivity.MST/1549

Strengthening of Cu–Ti alloys by addition of boron

Various Cu–Ti–B alloys were produced via argon atomisation at 1400°C. Rapidly solidified powders, containing dispersed TiB2 particles, were subsequently subjected to thermal treatment in hydrogen at temperatures between 300 and 600°C. This process resulted in the formation of fine, metastable Cu4Ti precipitates from the supersaturated solid solutions, which appreciably strengthened the copper matrix. Compared with the Cu–Ti powder particles obtained using the same procedure, the strengthening effect in Cu–Ti–B powder particles is much greater. The binary and ternary powders both reveal properties superior to those of Cu–Ti alloys produced via ingot metallurgy. This property is of interest for high conductivity electroengineering applications, since Cu–Ti–B alloys would provide a superior combination of strength and conductivity.MST/1549