Investigation of Microstructure of Al-5Ti-0.62C System and Synthesis Mechanism of TiC.

Wanwu Ding,Yan Cheng,Xiaoxiong Liu,Xiaoyan Zhao,Lumin Gou,Taili Chen

doi:10.3390/ma13020310

Abstract

Al-Ti-C master alloys have been widely investigated by various researchers. However, their refining effectiveness is still severely compromised by the preparation process. In this work, the aluminum melt in-situ reaction was carried out to synthesize the Al-5Ti-0.62C, and its refining performance was estimated. The thermodynamics calculation and differential scanning calorimeter experiment were used to investigate the synthesis mechanism of TiC. Quenching experiment was conducted to explore phase and microstructure transformation of the Al-5Ti-0.62C system. The results show that the main phases of Al-5Ti-0.62C master alloys are α-Al, Al3Ti, and TiC and it has a positive effect on commercial pure aluminum refining. Commercial pure aluminum is completely refined into the fine equiaxed structure by adding 0.3% Al-5Ti-0.62C master alloy. TiC particles mainly distribute in the grain interior and grain boundaries. The excess Ti came from the dissolution of Al3Ti spreading around TiC and finally forming the Ti-rich zone to promote the nucleation of α-Al. The experiments certified that TiC was formed by the reaction between solid C and excess Ti atoms. The main reactions in the Al-5Ti-0.62C system were that solid Al is transferred into liquid Al, and then liquid Al reacted with solid Ti to form the Al3Ti. At last, the release of a lot of heat promotes the formation of TiC which formed by the Ti atoms and solid C.

Highlights

Aluminum and its alloys have been widely used in military, aerospace, building, packaging, and electronics industries due to their excellent wear and corrosion resistance, low density, good high strength, high specific strength, and low efficiency of thermal expansion [1,2,3].Nowadays, with the development of the industry, it is urgent to improve multi-properties for aluminum alloys [4,5]
Al-5Ti-0.62C master alloy was added into the Al melt, and the dissolved Ti atoms will spread around the TiC particles to form the Ti concentration gradient, and form Al dendrite on the surface of the TiC particles by the Ti-rich zone, which demonstrate that TiC particles promote the α-Al nucleation
In the process of solidification, TiC particles are free in the melt at first, the excess Ti atoms segregate around TiC to form a concentration gradient

Summary

Introduction

Aluminum and its alloys have been widely used in military, aerospace, building, packaging, and electronics industries due to their excellent wear and corrosion resistance, low density, good high strength, high specific strength, and low efficiency of thermal expansion [1,2,3]. Some works have been undertaken to investigate the influence of prepared processing parameters on phase synthesis and refinement performance of Al-Ti-C master alloys. The in situ synthesis process of Al-Ti-C master alloys in aluminum melt by thermodynamic calculations and differential scanning calorimeter (DSC) experiment were analyzed [22,23,24,25]. The refining performance and phase distribution, morphologies, size of Al-T-C master alloys are seriously affected by the preparation process. This study provides a theoretical basis for the composition and process control of the Al-Ti-C master alloy. It facilitates the preparation of high efficient and stable master alloy

Experimental Materials and Methods

Results and Discussion

Phase Transformation and Microstructure Transformation of Al-Ti-C System

Conclusions