|Budget Amount *help
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1992: ¥100,000 (Direct Cost: ¥100,000)
Fiscal Year 1991: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1990: ¥1,500,000 (Direct Cost: ¥1,500,000)
1. Titanium hydride powders with particle sizes-100 and -325 mesh and atomized aluminum powders with particle diameters of 32 and 3 micrometers are mixed stoichiometricly and compacted uniaxially under 800MPa into cubes 10mm in size. The synthesizing reaction in the compact during sintering starts prior to the exothermic peak in a DTA curve. Beyond the peak temperature, the melting of aluminum particles decreases the sintered density in a short time. The exothermic peak is lower and the density higher with the slower rate 5K/min for example in the range 873-1173K which includes reaction temperatures. Total process time is shortened by increasing the rate to 20 K/min in ranges lower or higher than the 873-1173K range. After holding at 1703 K for 60min, TiAl is the major phase in the compact, with pores more round-shaped and less in number. The combination of the finer powders results in the fastest homogenization, the least dimensional change and the highest density, and is most suitable for machine parts.
2.In a uniaxially-pressed compact, aluminum particles deform and move into gaps between the hard titanium hydride particles which have rather non-deformed shapes. Since the hydrides approach more in the compacting direction, the number of the compacts between two of them per unit length in the compact is larger in the same direction than in the perpendicular ones. After the decomposition of the hydrides in the titanium particles, The aluminum melts and flows into the titanium particle boundaries, and then diffuses into the cores of the particles causing the expansion of the compact. The subsequent sintering brings the particles closer together. These mechanisms make both the expansion and the shrinkage larger in the compacting direction.