Influence Of Thermal History And Ti/C Ratios On The Morphological Characteristics Of TiC Synthesized Via The Al Melt Reaction Method

The influence of morphological characteristics of TiC synthesized through the Al melt reaction method were systematically studied using optical micrograph (OM), eletron-probe micro-analyzer (EPMA), X-ray diffraction (XRD), and field emission scanning electron microscope (FESEM), etc. By analyzing the differences of morphologies and grain sizes of TiC particles prepared through the different thermal histories and Ti/C ratios, the main influencing factors on morphology of TiC particles were discussed. At the same time, the nucleating ability of TiC particles with different grain sizes was investigated.The results showed that the grain sizes of TiC particles fabrieated at different thermal histories were different.When the highest temperature of melt is 1300℃, two different thermal histories were considered:(1) Increasing continuously temperature to 1300℃, then holding 15min at this temperature. On these conditions, the average size of TiC particles was about 1.5μm.(2) Increasing continuously temperature to 1100℃and holding 15min at the temperature, and then increasing continuously temperature to 1300℃, then holding 15min. On theses conditions, the average size of TiC particles was about 1.5μm.When the highest temperature of melt is 1500℃, three different thermal histories were discussed:(1) Increasing continuously temperature to 1500℃, then holding 15min at this temperature. In this case, the grain sizes of TiC particles were not uniform. The size of larger TiC particles was about 10.0μm and the morphologies were plates-like. The smaller size of TiC particles was about 1.5μm.(2) Increasing continuously temperature to 1300℃and holding 15min at the temperature, and then increasing continuously temperature to 1500℃, then holding 15min. In this case, TiC particles were uniform and the morphologies were block-like. The average grain size was about 1.5μm. (3) Increasing continuously temperature to 1400℃and holding 15min at the temperature, and then increasing continuously temperature to 1500℃, then holding 15min. In this condition, TiC particles were not uniform. The size of larger TiC particles was about 5.0μm and the morphologies were plates-like. The size of smaller TiC particles was about 1.5μm.The morphologies and grain sizes of TiC particles synthesized through Al melt reaction method were diverse because of different Ti/C ratios. The morphologies of TiC particles were like Polyhedron when Ti/C ratio is 12.5:1. The grain sizes of TiC are about 1.5μm at this condition. The morphologies of TiC particles were like irregular Polyhedron when Ti/C ratio is 4:1. The grain sizes of TiC particles were about 1.0μm at this condition.The morphologies of TiC particles were like Polyhedron when Ti/C ratio is 2.5:1. The grain sizes were from 1.0μm to 1.5μm.The nucleating abilitiy of TiC particles was affected by the grain sizes of the particles. When the average grain size of TiC particles was about 1.5μm, the nucleating ability was best. The a-Al was about 415μm when adding 0.2% Al-5Ti-0.25C master alloys with these TiC particles. When average grain size of TiC particles was about 5.0μm, theα-Al was about 470μm when adding 0.2% Al-5Ti-0.25C master alloys with these TiC particles. The nucleating ability was worst when average grain size of TiC particles was about 10.0μm. Theα-Al was about 485μm when adding 0.2% Al-5Ti-0.25C master alloys with these TiC particles. When the grain sizes of TiC particles were about 0.1～0.2μm, the a-Al was about 425μm when adding 0.2% Al-5Ti-0.25C master alloys with these TiC particles.