Al-Ti-C Master Alloys

(Project of the National Science Fund for Distinguished Young Scholars of China, National invention patents)

 

1. High Efficient Al-Ti-C alloys with Dispersed TiC Particles

  Grain refinement is widely used in aluminum alloys to improve the mechanical and chemical properties as well as processability. In the vast majority of grain refining applications, the Al–Ti–B master alloys are widely used and have remarkably promoted the development of aluminum alloys industry. But the Al-Ti-B master alloys also have exposed some problems in applications, which are as follows:

  • TiB2 particles are rather coarse (0.5-3μm) and have a tendency to agglomerate, leading to many quality problems. streak and porosity in thin foils, scratch-like linear surface defects in litho and bright-anodized sheet, internal cracking in extrusion billets as well as crack initiation in high strength aluminum alloy plate and forgings are all often blamed on coarse TiB2 clusters along with the filter blockage.
  • The nucleation efficiency of TiB2 is very poor (<1%) and most of TiB2 will become inclusion.
   It has been reported that the Al-Ti-C master alloys have key advantages comparing with Al-Ti-B master alloys. The TiC particles (with average size < 1μm) are much smaller than TiB2 and have much weaker tendency to agglomerate and higher nucleation efficiency.

  A new technology has been developed in our company to prepare Al-Ti-C master alloys with wide range of Ti:C ratios.

  1.1.Characteristics of our products

  • Sub-micron TiC particles are dispersed in the Al matrix evenly and their average size is smaller than 500nm.
  • TiC particles have excellent nucleation efficiency which is 5 times higher than that of TiB2 particles.
  • The grain refinement efficiency can be achieved within 1min and held on for 1 h without obvious fading

  The microstructures and the refinement performance of Al-Ti-C master alloys in our company are shown in Fig.1,2 and 3

The microstructure of Al-Ti-C ingot
The microstructure of Al-Ti-C rod

The microstructures of TiC at higher magnification
Fig.1 The microstructures of Al-Ti-C master alloys

Microstructures of commercial pure Al
Refined by 0.2%Al-5Ti-0.25C (within 2min)

Fig.2 The grain refining efficiency of Al-5Ti-0.25C master alloy

Fig.3 The microstructures of Al-1Ti-0.6C master alloy ingots

  1.2.Specifications of the products and Application Occasion

  The master alloys with a number of different titanium-to-carbon ratios are available in two forms: ingot and rod (Ф9.5). They can be used as refiners for aluminum wrought alloys, casting Al alloys, Zinc alloys and Magnesium alloys.

  • Usually 0.2wt% addition of Al-Ti-C master alloys is enough for commercial pure Al and aluminum wrought alloys to obtain enough refinement efficiency. It can promote the formation of fine equiaxed grains which help to improve the mechanical and chemical properties of alloys. Al-Ti-C master alloys can overcome the disadvantages of Al-Ti-B master alloys such as the agglomeration of coarse TiB2, so they are especially suitable for application in the production of aluminum foil or plate.
  • It is found that the Al-Ti-C master alloys with Ti:C ratio below 4:1 are potential refiners for Magnesium alloys.
   Notice.1 Al-Ti-C master alloy can not refine Al-Si alloys with Si content higher than 7% (wt.%).
   Notice.2 The special refinement technology is needed for refining the Al alloys with Zr.

  We have a series of Al-Ti-C mater alloys such as Al-5Ti-0.25C, Al-5Ti-0.35C, Al-5Ti-0.5C, Al-2Ti-0.8C and so on. They are all commercially available to be used in different alloys. The detailed application occasions of them are shown in Table.1

Table. 1 The specifications, compositions and usages of series of Al-Ti-C master alloys

Specification

Ti

C

Others total

Usage

AlTi5C0.5

4.6-5.4

0.4-0.6

0.6

Grain Refinement for Wrought Aluminum Alloys 

AlTi5C0.25

4.6-5.4

0.2-0.3

0.6

AlTi3C0.15

4.2-4.8

0.1-0.2

0.6

 

2.Technical support
   We have been authorized three national invention patents about Al-Ti-C master alloys. In addition, we have also researched the fabrication, application, refinement performances and nucleation mechanisms about the master alloys, and following publications may be helpful for you and your company. For additional information or technical assistance, please contract us by e-mail or other manner.

  1. Ding Haimin, Liu Xiangfa, Yu Lina. The influence of forming processes on the distribution and morphologies of TiC in Al–Ti–C master alloys, Scripta Materialia, 2007; 57: 575-578
  2. Haimin Ding, Xiangfa Liu, Lina Yu. Influence of zirconium on grain refining efficiency of Al–Ti–C master alloys, Journal of Material Science, 2007; 42:9817–9821
  3. Yu Lina, Liu Xiangfa, Wang Zhenqing, Liu Jianwen. Instability of TiC and TiAl3 compounds in Al-10Mg and Al-5Cu alloys by addition of Al-Ti-C master alloy, Journal of University of Science and Technology Beijing: Mineral Metallurgy Materials (Eng Ed), 2006; 13(2) : 145-148
  4. Wang Zhenqing,Liu Xiangfa, Bian Xiufang. Reaction in the Al-TiO2-CB4 System and in Situ Synthesis of an Al/(TiC+TiB2+a-Al2O3) Composite. Advanced Engineering Materials,2004; 6(12): 276-281
  5. Wang Zhenqing,Liu Xiangfa, Zhang Junyan and Bian Xiufang. The Reaction Mechanism in Al-C Binary System Through DSC and XRD,Journal of Materials Science,2004;39(6): 2179-2181
  6. Wang Zhenqing, Liu Xiangfa and Bian Xiufang. Reaction mechanism in an Al-TiO2-C system for producing in-situ Al/(TiC+Al2O3) composite, Journal of Materials Science 2004;39(2):663-666
  7. Liu Yanhui, Liu Xiangfa,Bian Xiufang.Grain refinement of Mg-Al alloys with Al4C3-SiC/Al master alloy, Materials Letters,2004;58( 7-8):1282-1287
  8. Wang Zhenqing, Liu Xiangfa and Bian Xiufang. Microstructure and its influence on refining performance of AlTiC master alloys, Materials Science and Technology, 2003;19 (12):1709-1714
  9. Wang Zhenqing, Liu Xiangfa and Bian Xiufang. Reaction mechanism in the ball-milled Al-C powders, Journal of Materials Science Letters,2003; 22:1427-1429
  10. Liu Xiangfa, Wang Zhenqing, Zhang Zuogui, Bian Xiufang. The Relationship between Microstructures and Refining Performances of Al-Ti-C Master Alloys. Materials Science and Engineering A, 2002; A332: 70-74

 

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