(哈爾濱工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，哈爾濱 150001)
摘 要: 利用掃描電鏡、X射線(xiàn)衍射儀和透射電鏡對(duì)6 GPa高壓下凝固的Al-9.6%Mg合金的顯微組織以及組織的穩(wěn)定性進(jìn)行研究，對(duì)高壓亞穩(wěn)相形成機(jī)理進(jìn)行探討。結(jié)果表明：常壓下枝晶間大量存在的Al3Mg2相在高壓凝固時(shí)消失，形成另一密排六方結(jié)構(gòu)相；經(jīng)300 ℃, 11 h時(shí)效處理后，組織變得不穩(wěn)定，六方結(jié)構(gòu)相消失，轉(zhuǎn)變成穩(wěn)定的Al3Mg2相，但其形態(tài)由常壓下三岔分界形式轉(zhuǎn)變成團(tuán)狀，由此推斷該六方結(jié)構(gòu)相為亞穩(wěn)相；在高壓凝固條件下Mg在Al基體中的固溶度由7.74%增大到11.3%，Al相的晶格常數(shù)增加, 在XRD圖中表現(xiàn)為Al相衍射峰左移，但經(jīng)時(shí)效處理后，Al相衍射峰基體又回復(fù)到常壓時(shí)的位置。
關(guān)鍵字: 高壓凝固組織；Al-Mg合金；時(shí)效處理
and stability of Al-9.6%Mg alloy
（School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China）
Abstract:The microstructure and its stability were investigated when Al-9.6%Mg alloy was solidified under 6GPa high pressure using SEM, XRD and TEM. The formation mechanism of high pressure metastable phase was discussed. The results show that a hexagonal phase forms under high pressure solidification conditions instead of a great amount of interdendritic Al3Mg2 phases under normal pressure. This phase disappears after aging treatment (300 ℃, 11 h), and they are transformed into the stable Al3Mg2 phase, but its morphology changes from the branching to agglomerate. So it is deduced that the hexagonal phase formed at 6 GPa pressure is a metastable phase. In addition, the solid solubility of Mg in Al matrix increases from 7.74% to 11.3%, and the lattice constant of α(Al) phase also increases, the diffraction peaks of Al move to the left in XRD patterns. However, the position of the diffraction peaks of Al is almost the same as that of normal pressure after aging treatment.
Key words: high pressure solidification microstructure; Al-Mg alloy; aging treatment
