(1. 北京科技大學 新金屬材料國家重點實驗室，北京 100083；
2. 北京科技大學 材料科學與工程學院，北京 100083；
3. 北京有色金屬研究總院，北京 100088)
摘 要: 利用噴射成形技術制備AZ91、AZ92和AZ93鎂合金沉積柱坯，并對其微觀組織演變進行觀察。結果表明：鑄態(tài)普通凝固AZ91合金的晶粒粗大，脆性β-Mg17Al12相連續(xù)分布成網狀結構；而噴射成形AZ91、AZ92和AZ93合金的組織均勻，晶粒被充分細化，β-Mg17Al12相的網狀結構被打破；噴射沉積快速凝固條件下高的冷卻速率促進了過飽和α-Mg固溶體組織的形成，使得偏析相減少，形態(tài)改善；Zn含量的增加降低了Al在Mg中的溶解極限，促進了β-Mg17Al12相在晶界的析出及α-Mg+β-Mg17Al12離異共晶組織的形成；Zn元素的偏析傾向為激活成分過冷區(qū)內的形核質點提供了驅動力，從而阻礙了晶粒長大。
關鍵字: 鎂合金；噴射成形；微觀組織
（1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing,
Beijing 100083, China;
2. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China;
3. Beijing General Research Institute for Nonferrous Metals, Beijing 100088, China）
Abstract: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.
Key words: magnesium alloy; spray-forming; microstructure
