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本文研究了用流变铸造法生产的含44、49及54(原子)%Al的 TiAl 二元金属间合金的显微组织细化和机械性能改善。流变铸造,是在氩气气氛下,把搅动器插入合金熔体中,使凝固中的金属在15及70转/秒高旋转速度下被激烈揽动。在流变铸造的 Ti-44(原子)%Al 合金显微组织中,那种在不经搅动而凝固的合金中所见到的层状组织已被完全破坏,而形成了由弥散聚合体组成的特别细的显微组织。在70转/秒旋转速度下流变铸造的 Ti-44%Al 合金的聚合体和单个晶粒的平均大小,在长轴方向分别为6.4±3.7μm和2.2±1.3μm,在短轴方向分别为2.0±1.1μm和为1.0±0.6μm。可是,流变铸造的 Ti-49(原子)%Al 合金的显微组织中发现有椭圆形层状晶;而在流变铸造的 Ti-54(原子)%Al 合金显微组织的椭圆形初晶中还发现有层状亚结构。在70转/秒旋转速度下流变铸造的 Ti-44%Al 合金的显微分析中发现,虽然在不经搅动凝固的舍金中有层状偏析,但流变铸造合金中由于搅动碎化了层状组织,因而使铝和钛元素得到了均匀分布。在15转/秒和70转/秒转速下搅动流变铸造的 Ti-44%Al 合金室温下的延伸率分别为2.7%和3.3%。均高于未经搅动而凝固的合金的延伸率(即2%)。在15和70转/秒旋转速度下流变铸造的 Ti-44%Al 合金的室温下的抗拉强度分别为359和468MPa,它们同样高于未经搅动凝固的合金的抗拉强度245MPa。虽然,流变铸造的 Ti-44%Al 合金的高温延伸率和抗拉强度存在一些波动,但它比未经搅动凝固的合金都有所改善。在70转/秒旋转速度下流变铸造的与未经搅动凝固的合金的抗拉强度,在1173K 温度下分别为538和363MPa,在1273K 温度下分别为439和389MPa。
In this paper, the microstructure refinement and mechanical properties of TiAl binary intermetallic alloys containing 44, 49 and 54 (atomic)% Al produced by rheo-casting were investigated. Rheo-cast is the insertion of an agitator into the alloy melt under an argon atmosphere so that the solidified metal is fiercely stirred at a high rotational speed of 15 and 70 rev / sec. In the rheo-cast Ti-44 (atomic)% Al alloy microstructure, the lamellar structure seen in the alloy solidified without agitation has been completely destroyed to form a microstructure composed of dispersed polymer The special fine microstructure. The average size of the aggregates and individual grains of the rheo-cast Ti-44% Al alloy at a rotation speed of 70 rev / sec were 6.4 ± 3.7 μm and 2.2 ± 1.3 μm in the long axis direction, respectively 2.0 ± 1.1 μm and 1.0 ± 0.6 μm. However, an elliptical layered crystal was found in the microstructure of the rheo-cast Ti-49 (atomic%) Al alloy. In the case of the elliptically shaped Ti-54 (atomic%) Al alloy microstructure of rheo-cast Also found in the crystal layered substructure. Microscopic analysis of the rheo-cast Ti-44% Al alloy at a rotational speed of 70 revolutions per second found that although layered segregation was present in the sacrificial gold that had not been agitated by agitation, the rheological cast alloy was degraded by agitation Layered structure, so that aluminum and titanium elements are evenly distributed. Tensile cast Ti-44% Al alloys were agitated at room temperature for 15% and at a revolution of 70 rpm at room temperature with 2.7 and 3.3% elongation, respectively. All of them were higher than the elongation (ie, 2%) of the alloys that were set without agitation. Tensile strengths of the rheo-cast Ti-44% Al alloys at room temperature of 15 and 70 rev / sec were 359 and 468 MPa, respectively, which were also higher than the tensile strengths of the alloys unanodized and coagulated at 245 MPa. Although the rheological cast Ti-44% Al alloy has some fluctuations in the high temperature elongation and the tensile strength, it is better than the alloy without solidification. Tensile strengths of the rheocasting and un-churned alloys at a rotational speed of 70 rev / sec were 538 and 363 MPa at 1173K and 439 and 389 MPa at 1273K, respectively.