γ-ΤiAl增压涡轮近净形铸造过程实验研究

Experimental Research on the Near Net Shape Casting Process of Gamma Tita nium Aluminide Turbochargers

γ-TiAl金属间化合物的成形工艺是材料成形领域的前沿领域和研究热点。本研究采用水冷铜坩埚真空感应凝壳技术和熔模型壳离心浇注的铸造方法制备γ-TiAl增压涡轮,通过改善冒口工艺获得了健全的γ-TiAl涡轮铸件,分析了γ-TiAl增压涡轮的凝固过程和收缩缺陷产生原因。结果表明,增大冒口与铸件的模数之差以及冒口与铸件的体积之比有利于减少及消除涡轮铸件的收缩缺陷。为给数值模拟研究提供热物性参数,针对涡轮铸件用钛铝合金,实验测试了合金的热膨胀系数、比热和热导率等物性参数,其与温度的关系分别为:α1=8.10651+0.0073T-2.97619E-6T2;CP=668.28158-0.013T+1.11905E-4T2;=19.82252-0.02781T+6.51497E-5T2-3.21096E-8T3。

The research on forming process of gamma titanium aluminide is at the frontier in the field of materials processing. Using water cooling copper crucible, the titanium aluminum alloy was melted by ISM technique, and gamma titanium aluminide turbochargers were produced by centrifugal investment precision casting process. Adopting optimizing design,of risers, sound turbochargers were prepared, and solidification process and shrinkage defects of turbocharger castings were analyzed.. The results showed that shrinkage defects of turbochargers could be decreased or eliminated when the modulus difference between riser and casting or the volume ratio of riser to casting were increased. In order to provide numerical simulation study with thermal property parameters, coefficient of thermal expansion, specific heat and,coefficient of thermal conductivity of the titanium aluminium alloy were measured. The relations between them and temperature could be expressed respectively as: alpha(1) = 8.106 51 + 0.007 3 T - 2.976 19 E - 6T(2); C-P = 668.281 58 - 0. 013T + 1.119 05 E - 4T(2); lambda = 19.822 52 - 0.027 81T + 6.514 97 E - 5T(2) - 3.210 96 E - 8T(3).