定向凝固組織的影響
(江蘇大學(xué) 材料科學(xué)與工程學(xué)院，鎮(zhèn)江 212013)
摘 要: 分別在750、850、950和1 050 ℃下，研究熔體過熱處理對(duì)Al-4.7%Cu(質(zhì)量分?jǐn)?shù))合金定向凝固組織的影響，利用綜合熱分析儀測定Al-4.7%Cu合金熔體結(jié)構(gòu)特征及變化過程。結(jié)果表明：經(jīng)過950 ℃和1 050 ℃過熱處理的一次枝晶間距比在750 ℃常規(guī)過熱直接定向凝固的分別減小了31.2%和36.2%；隨著熔體過熱時(shí)間的延長，一次枝晶間距減小，組織越來越細(xì)密；但隨著低溫保持時(shí)間的延長，一次枝晶間距增大，組織越來越粗大，表明熔體高溫處理對(duì)定向凝固組織形態(tài)的影響逐漸衰退；熔體過熱處理對(duì)Al-4.7%Cu合金定向凝固組織有顯著影響的原因在于熔體過熱處理改變了熔體結(jié)構(gòu)狀態(tài)。
關(guān)鍵字: 定向凝固；過熱處理；一次枝晶間距；熔體結(jié)構(gòu)；凝固組織
on directional solidification microstructure
of Al-4.7%Cu alloy
（School of Materials Science and Engineering, Jiangsu University,
Zhenjiang 212013, China）
Abstract:The influence of melt superheat treatment on the directional solidification microstructure of Al-4.7%Cu(mass fraction) alloy was studied at 750, 850, 950 and 1 050 ℃, respectively. The characteristics of the melt were measured by integrated thermal gravimetric analyzer. The results show that the primary dendrite arm spacing of the superheated samples at 950 and 1 050 ℃ decreases 31.2% and 36.2%, respectively, compared with the sample treated at 750 ℃. Along with the increase of melt superheat time, the primary dendrite arm spacing decreases and the microstructure is refined. However, if the melt stays at low temperature for a long time, the primary dendrite arm spacing increases and the microstructure coarsens, which indicates that the effect of melt superheat treatment on the morphology of directional solidification microstructure declines. The radical reason is that the superheat treatment makes the alloy microstructure changed.
Key words: directional solidification; superheat treatment; primary dendrite arm spacing; melt structure; solidification microstructure
