Combustion Synthesis and Sintering of TiAl Intermetallic Compounds and Net Shape Manufacturing of Machine Parts.

TiAl金属间化合物的燃烧合成和烧结以及机器零件的净形制造。

• 批准号: 02650098
• 负责人: KUROKI Hidenori
• 金额: $ 1.22万
• 依托单位: HIROSHIMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1990
• 资助国家: 日本
• 起止时间: 1990 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02650098/
• 关键词: Titanium Aluminide; Liquid Phase Sintering; Combustion Synthesis; Selfpropagating High Temperature Synthesis; 金属間化合物; チタン; アルミニウム; 粉末; 寸法変化率; 反応焼結; 膨張率

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.

1.将粒度为-100目和-325目的氢化钛粉末与粒度为32 μ m和3 μ m的雾化铝粉按化学计量混合，并在800MPa下单轴压制成10mm大小的立方体。烧结过程中压坯中的合成反应在DTA曲线中的放热峰之前开始。在峰值温度以上，铝颗粒的熔化在短时间内降低了烧结密度。在包括反应温度在内的873 - 1173K范围内，在较慢的速率5K/min下，放热峰较低，密度较高。通过在低于或高于873 - 1173K范围内将速率增加到20K/min来缩短总处理时间。在1703 K保温60 min后，压坯中的相主要为TiAl，气孔形状较圆，数量较少。较细粉末的组合导致最快的均匀化，最小的尺寸变化和最高的密度，并且最适合于机械部件。2.在单轴压制坯中，铝颗粒变形并移动到具有相当非变形形状的硬质氢化钛颗粒之间的间隙中。由于在压实方向上，两个压坯之间的压坯数量在同一方向上比在垂直方向上多，因此在压坯中每单位长度上两个压坯之间的压坯数量更多。在钛颗粒中的铝分解后，铝熔化并流入钛颗粒边界，然后扩散到颗粒的芯部，引起压坯的膨胀。随后的烧结使颗粒更紧密地结合在一起。这些机制使膨胀和收缩都在压实方向上更大。