Effect Of Born On The Grain Refinement Of Titanium Added By Electrolysis And Application In Preparation Of Al-Si Alloy

With the existing pure aluminum production facility, Low-titanium alloy are produced by direct electrolysis, which is a new method of adding titanium. In this paper, this method of adding titanium by electrolysis is described simply, and the studies about the electrolytic low- titanium alloy are generalized. Based on the existing studies, the following work done by author is described in this paper.Firstly, the effect of born on the grain refinement effectiveness and fading behaviors of titanium added by electrolysis were investigated by adding Al-B master alloy to the electrolytic low- titanium alloy. The amount of the Al-B master alloy added to the low-titanium aluminum alloy was determined according to the Ti/B mass ratio of 5:1. The experiment results show that the addition of B improves the grain refinement effectiveness and the resisting fading ability of titanium added by electrolysis.Secondly, according to different B/Ti mass ratio, Al-B master alloy was added to the electrolytic low-titanium aluminum alloys to investigate the effect of B/Ti mass ratio on the grain refinement effectiveness of titanium. The results show that the grain sizes are very small when the B/Ti mass ratios are lower than 1:2.22 (the stoichiometric value for TiB₂); The best grain refining effectiveness is obtained at the B/Ti mass ratio of 1:10; The grain refinement capacity vanishes completely when B/Ti mass ratio reaches 1:2.22, and the grains exhibit coarse columnar structure. It implies titanium in the melt reacted to born to form TiB₂ particles completely, and the TiB₂ particles alone have not grain refinement; The grain size decreases slowly again when the B/Ti mass ratio is higher than 1:2.22, but the grain size is far bigger than that of electrolytic low-titanium alloy without B. Comparing the variations of grain sizes of electrolytic low-titanium alloy with increasing excess B (over thestoichiometric ratio for TiB2 phase) with that of pure aluminum versus the B contents, the results show that the patterns of two variations appear very similar. It can be inferred that the excess B in the melt can not transfer the TiB2 particles into the effective nuclei for aluminum. The excess Ti existed in the melt, which exceeds the stoichiometric ratio for TiB2 phase, plays a key role in the grain refinement of T1B2 particles.Thirdly, in the laboratory condition, A356 alloys were prepared using the electrolytic low- titanium. At the mean time, the same brand alloys were made with pure aluminum by fusion alloying, which were refined with Al-5Ti master alloy and Al-5Ti-lB master alloy respectively. The microstructure and mechanical properties of the A356 alloys refined by titanium added by electrolysis, Al^. 5Ti master alloy and Al-5Ti-lB master alloys were compared and studied. The result show that the mechanical properties of the A356 alloys made with the low-titanium aluminum alloy are as good as that refined by Al—. 5Ti master alloy and Al-5Ti-lB master alloys at least.At last, the industrial test of A356 alloy with electrolytic low content titanium melt produced in industrial aluminum electrolyzer was conducted, and the structure and properties of the A356 alloy produced in industrial test were tested and analyzed. The results show that the A356 alloys have uniform structure and good properties. Their mechanical properties are equal to that of A356 alloys made in laboratory. It can be implied that it is feasible that Al-Si alloys are directly produced by making use of electrolytic low content titanium aluminum alloy melt. And this method has the characteristics of consuming less energy, simple refining technological process and good product quality.