The impact toughness of A356 alloys with the same ratio of w(Ti)/w(B) and the same titanium content
produced by different Ti and B alloying methods were investigated. The results show that the Ti、B alloying methods has an obvious effect on the microstructure and impact toughness of A356 alloys.
The A356 alloys produced by electrolytic low-titanium aluminium alloys have the optimum grain refinement effect and impact toughness. The reason is that the refinement of microstructure increases the growth free path of microcrac. The microcrack growth need absorb higher propagation energy. Though the impact toughness of A356 alloys refined with electrolytic low-titanium aluminium alloys+Al-B master alloys almost has the same values as that alloys alloyed with melting Al-Ti-B master alloys and melting K2TiF6+KBF4
the former alloys have the higher fracture resistance than that of the latter alloys because of the former alloys have higher crack propagation energy.