CAJ | 학술논문

利用喷射成形技术制备AZ91、AZ92和AZ93镁合金沉积柱坯,并对其微观组织演变进行观察.结果表明:铸态普通凝固AZ91合金的晶粒粗大,脆性β-Mg17Al12相连续分布成网状结构;而喷射成形AZ91、AZ92和AZ93合金的组织均匀,晶粒被充分细化,β-Mg17Al12相的网状结构被打破;喷射沉积快速凝固条件下高的冷却速率促进了过饱和α-Mg固溶体组织的形成,使得偏析相减少,形态改善;Zn含量的增加降低了Al在Mg中的溶解极限,促进了β-Mg17Al12相在晶界的析出及α-Mg+β-Mg17Al12离异共晶组织的形成;Zn元素的偏析倾向为激活成分过冷区内的形核质点提供了驱动力,从而阻碍了晶粒长大.
이용분사성형기술제비AZ91、AZ92화AZ93미합금침적주배,병대기미관조직연변진행관찰.결과표명:주태보통응고AZ91합금적정립조대,취성β-Mg17Al12상련속분포성망상결구;이분사성형AZ91、AZ92화AZ93합금적조직균균,정립피충분세화,β-Mg17Al12상적망상결구피타파;분사침적쾌속응고조건하고적냉각속솔촉진료과포화α-Mg고용체조직적형성,사득편석상감소,형태개선;Zn함량적증가강저료Al재Mg중적용해겁한,촉진료β-Mg17Al12상재정계적석출급α-Mg+β-Mg17Al12리이공정조직적형성;Zn원소적편석경향위격활성분과랭구내적형핵질점제공료구동력,종이조애료정립장대.
The billets of AZ91, AZ92 and AZ93 magnesium alloys were synthesized by the spray-forming (SF) processing. The microstructure evolution of the alloys was observed. The microstructure analysis shows that the microstructure of the conventional as-cast AZ91 alloy consists of coarse grains, and the brittle β-Mg17Al12 phases distribute along the grain boundaries continuously to form network. The grains of the as-sprayed AZ91, AZ92 and AZ93 alloy are homogeneous and refined, and the networks of brittle β-Mg17Al12 phases are broken. The rapid solidification process under a higher supercooling condition can remarkably increase the forming of supersaturated microstructure of α-Mg, which results in the absence of macrosegregation and the improvement of precipitated phase shape. The solution limitation of Al in Mg decreases with increasing addition of Zn. The high content of Zn accelerates the precipitation of β-Mg17Al12 phases along the grain boundary and formation of α-Mg+β-Mg17Al12 divorce eutectic structure. The grain growth is limited because the segregation tendentiousness of Zn offers drive force for activation of nucleation sites in the component undercooling area.