Effect Of The Ti,B Alloying Methods On The Grain Refinement And Mechanical Properties Of A356 Alloys

In this paper, aiming at the grain refinement of A356 alloys, seven kinds of A356 alloys with different ratio of Ti/B are produced by different Ti, B alloying such as directly electrolytic low-titanium aluminium alloys(EA356),melting Al-Ti master alloys(MA356), melting K₂TiF₆(MKTA356X electrolytic low-titanium aluminium alloys+Al-B master alloys(ETBA356), melting Al-Ti-B master alloys(MTBA356), electrolytic low-titanium aluminium alloys+ KBF₄ (ETKBA356)and melting K₂TiF₆+KBF₄(MKTBA356). The effect of Ti and B alloying methods and the ratio of Ti and B on the grain refinement effect, fading resistance and mechanical properties are systemically investigated. The grain refinement mechanism, fading mechanism and strengthening mechanism are discussed.The experimental results show that the grain of A356 alloys can be effectively reduced when adding titanium into melt using any methods. If the same titanium content, the EA356 alloys have the optimum grain refinement effect and fading resistance. The MKTA356, however, has the worst grain refinement effect and fading resistance. Ti alloying methods also have an effect on the modification and fading behavior of eutectic silicon particles. Similar to the effect of grian refinement, modification effect of eutectic silicon particles in the EA356 alloys is the most excellent, while that of MKTA356 is the worst. It can be attributed to the effect of the titanium methods, volume fraction and distribution of Al₃Ti particles in melt and their dissolving and settling when holding for a longer time.The complex refinement with Ti and B can obviously improve the effect of grain refinement. The ETBA356 alloys have the optimum grain refinement effect and fading resistance. While that of the MKTBA356 is the worst. For all the Ti and B alloying methods, when the ratio of Ti and B added into the melt is approached to the stoichiometric proportion of TiB₂, the alloys have the worst grain refinement effect. When the ratio of Ti and B added into the melt is 1:3, the optimum grain refinement effect is obtained. Both over or low this...