连续等通道转角挤压对Al-Ti-C合金组织与性能的影响

Effect of continuous equal channel angular pressing on microstructure and properties of Al-Ti-C alloy

采用连续等通道转角挤压工艺,以连续的方式对Al-Ti-C合金进行多道次挤压,通过观察微观组织演化,探讨晶粒细化机理和力学性能变化。结果表明:连续等通道转角挤压工艺可有效细化Al-Ti-C合金微观组织,晶粒尺寸减小至1μm左右,形变诱导是变形过程中最主要的晶粒细化机制;高密度位错堆积引起Al基体和TiAl_(3)界面的裂纹以及TiAl_(3)内部的空洞产生,裂纹进一步扩展贯穿整个TiAl_(3)颗粒,最终导致第二相TiAl_(3)组织的细化,同时细小的第二相TiAl_(3)组织的钉扎机制和剪切机制促进了Al基体细化;连续等通道转角挤压1道次后,合金硬度提升最明显,与原始态相比提高59.2%;之后随挤压道次的增加,硬度提升的趋势变缓,合金塑性下降,韧性提高。

The Al-Ti-C alloy was extruded in multiple passes in a continuous manner by continuous equal channel angular pressing process.Through observation of the microstructure evolution,the mechanism of grain refinement and changes in mechanical properties were discussed.The results show that continuous equal channel angular pressing process can effectively refine the microstructure of Al-Ti-C alloy,and the grain size is reduced to about 1μm.The deformation induction is the most important grain refinement mechanism in the deformation process.The accumulation of high density dislocations causes cracks at the interface between the Al matrix and TiAl_(3)and voids inside the TiAl_(3).The cracks further propagate through the entire TiAl_(3)particles,ultimately leading to the refinement of the second phase TiAl_(3)structure.At the same time,the pinning mechanism and shearing mechanism of the fine second phase TiAl_(3)structure promote the refinement of the Al matrix.After one pass of continuous equal channel angular pressing,the hardness of the alloy increases most obviously,which is 59.2%higher than that of the original state.With the increase of the number of extrusion passes,the increasing trend of hardness slows down,the plasticity of the alloy decreases,and toughness increases.