Sc And Mn, Ti Composite Micro-alloying Of Al-mg Alloy,

Six kinds of Al-Mg alloy containing different percents of Sc Mm Ti were prepared using ingot metallurgy processing .The room-temperature tensile mechanical properties of these alloys at different annealing temperature(130℃/3h, 340℃/lh) were measured. The microstructures of these alloys at various treatments were evaluated using optical microscopy .transmission electron microscopy(TEM) and scanning electron microscopy(SEM). The effect of combinations of minor Sc and Mn Ti additions on microstructure and tensile properity of Al-Mg alloy has been investigated .The existing forms and acting mechanisms of minor Sc Mn and Ti in Al-Mg alloy were discussed. 'We also discussed the behavior of annealing-hardening of the both as-cast alloy(Al-Mg-Sc-Mn and Al-Mg-Sc-Ti) in the article .The results are as follows.The combinations of minor Sc and Mn can considerably improve the tensile mechanical properties of Al-Mg alloy. When Sc additions are 0.25wt% and Mn additions are 0.4wt% in Al-5.5Mg alloy, o b can improve 54-67MPa and o()2 can improve 64-67MPa and 5 maintains on high level (>11%). When Sc additions are 0.25wt% and Ti additions are 0.04wt% in Al-5.5Mg alloy, ob can improve 44-46MPa and oft2 can improve 39-70MPa and 6 maintains on high level(>13%).The combinations of minor Sc and Mn or Sc and Ti can improve the as-cast microstructure and inhibit recrystallization of Al-Mg alloy.Their existing forms in Al-Mg alloy is AlsSc (FeMn) A16 orA!3(Sc,Ti).The strengthening mechanisms of combinations of Sc and Mn or Sc and Ti in A!-Mg Alloy are that the former is considered as substructure strengthening and dispersion strengthening and the later is considered as fine grain strengthering ,substructure strengthening and dispersion strengthening.Both alloy of Al-Mg-Sc-Mn and Al-Mg-Sc-Ti have considerable annealing-hardening behavior. With the annealing temperature improving, the hardness of the alloys increases; as temperature reaches to 300℃, the hardness of the alloys reaches the maximum;laterly with the annealing temperature increasing the hardness decreases.When the annealing temperature is under 350℃, the hardness of Al-Mg-Sc-Mn alloy is higher than Al-Mg-Sc-Ti alloy;and when the annealing temperature is 350 ℃, the hardness of the both alloy is on thesame level; but when the annealing temperature is above 350 , the hardness of Al-ivIg-Sc-Ti alloy is better than Al-Mg-Sc-Mn.