Abstract
Workability and aging behavior of Mg-Li-Al alloys hate been investigated with variation of Li and Al contents. It was found that ${\alpha}$(HCP) + ${\beta}$(BCC) two phase structure reveals better workability than ${\alpha}$(HCP) single phase structure. Increase of workability is attributed to the additional slip on pyramidal and prism planes besides the slip on basal plane of HCP Mg. Workability of ${\alpha}$+${\beta}$ two phase structure is improved with increased amount of Al. Among alloys studied in the present study, reduction limit up to 62 % was obtained for Mg-8.08Li-4.26Al. MgL$i_2$Al(${\theta}$) aging precipitation was observed in ${\alpha}$+ ${\beta}$ two phase structure, while it was not in a single phase structure. Result of microhardness reveals peak hardness for ${\alpha}$ +${\beta}$ two phase structure due to $\theta$ precipitate in ${\theta}$ phase. In ${\alpha}$+${\beta}$ two phase Mg-Li-Al alloys, hardness increased with increasing amount of Al. It is believed that addition of Al raised the amount Al partition in u phase and ${\theta}$ precipitation in ${\beta}$ phase.
Li의 양과 Al의 양을 달리한 $\alpha$(HCP) 단상 및 $\alpha$(HCP)+${\beta}$ (BCC) 2상 조직인 Mg-Li-Al합금을 시료로 하여 이 합금의 가공성과 시효경화륵성을 조사한 결과 $\alpha$단상보다는 $\alpha$+${\beta}$ 2상 조이,$\alpha$+${\beta}$ 2상조직에서는 Al양이 많을수록 가궁성이 증가하였으며 Mg-8.08Li-4.26Al의 경우 가공한계값은 62%였다. 이와같이 가공성이 증가한 이유는 basal plane뿐만 아니라 pyramidal plane과 prism plane에서도 슬립이 일어났기 때문이다. $\alpha$단상의 경우 MgL$i_2$ Al(${\theta}$)의 석출이 일어나지 않았으나 $\alpha$+${\beta}$ 2상 조직의 곁우 ${\beta}$상 내에서 ${\theta}$의 석출에 의한 피크경도같이 나타났으며, 2상 조직의 경우 경도값은 Al양이 많을수록 증가하였는데 이것은 Al양의 증가에 따른 Al Partition에 의한$\alpha$ 상의 강화와 ${\beta}$상에서의 석출물 증가에 의한 것으로 생각된다.
