The Research On Conform-ECAP Of Al/TiAl₃ Composite

The particulate reinforcing Al metal matrix composites have some advantages such as simple produce technics, low cost and high performance et al, which has been a hot topic on researching in the MMCs. But there have some disadvantages such as lower density and unequable destributing, which has impaired the mechanics property and limited the apply in the industry.This paper developed a new continuous equal channel angular pressing (Conform-ECAP) technique, which successfully produced severe plastic deformation (SPD) of Al/TiAl3 composite with ultra-fine grains (UFG), Al/TiAl3 composite was pressed by eight passes. The evolutions of Al/TiAl3 composite before and after deformation were researched by using optical microscope and transmission electron microscopy. The grain refinement mechanism was further researched. The ultimate hardness and wear-resisting property were tested after pressing. The change of TiAl3 particulates and deformation inter-action in the Conform-ECAP were studied.The results indicate that the grains of Al/TiAl3 composite were reduced effectively by the Conform-ECAP technique. The grain sizes were reduced from original annealing～35μm to 0.4～0.8μm after pressing by eight passes. The deformation induction is the most important grains refinement mechanism of Conform-ECAP.After Conform-ECAP deformation, the hardness and the strength were increased consumedly and improved the mechanics property. The proportion of the big TiAl3 reinforcing particulates reinforcement was suddenly decreased, and the reinforcing particulate sizes were broken from the original annealing 8～10μm to 3～4μm, and the distribution of the reinforcing particulates in the Al/TiAl3 composite were improved awfully. However, twinning TiAl3 was found after pressing by eight passes, which suggested that some larger reinforcing particulates could not be eliminated entirely, and some compatibility of deformation mechanism was presented. The microstructure after eight passes was composed of large quantity of small reinforcing particulates and small quantity of big reinforcing particulates.The tissue of the Al/TiAl3 composite was instable by the Conform-ECAP, the parameter of heating stability was ensured by testing the hardness after pressing:the annealing for four hours at 250℃and two hours at 250℃respectively after pressing by one pass and four passes.