(華南理工大學 機械與汽車工程學院，廣州 510640)
摘 要: 采用直接擠壓鑄造工藝制備一種密度為2.525 g/cm3 的A1-2.47Li-1.49Cu 合金鑄錠，通過宏觀腐蝕、OM、DSC、SEM、XRD 及拉伸性能測試等手段對其組織和力學性能進行研究。結果表明：壓力作用下凝固可以顯著改善鑄錠的表面質量，獲得致密無縮松缺陷的鑄錠，50 MPa 下，鑄錠中的柱狀晶平均長度較重力鑄造下的減小20%；合金鑄態(tài)微觀組織主要由初生α(Al)、T2 相以及少量AlLiSi 和Al6(CuFe)組成，施加壓力不改變相的組成，但可使第二相尺寸更小，分布更均勻；合金硬度、抗拉強度以及伸長率均隨壓力增大而增大，但50 MPa 以后壓力對性能的影響不明顯。50 MPa 下T5 熱處理的合金抗拉強度為329 MPa，伸長率為6%，硬度為135HBS，較重力鑄造合金分別提高了7.2%、107%和3%。
關鍵字: Al-Li-Cu 合金；擠壓鑄造；組織；力學性能
（School of Mechanical and Automotive Engineering,South China University of Technology,Guangzhou 510640,China）
Abstract:Al-2.47Li-1.49Cu alloy ingot with density of 2.525 g/cm3 was prepared by direct squeeze casting. The macroand micro-structures and mechanical properties of the alloy were analyzed by macro corrosion,OM,DSC,SEM,XRD and tensile properties test. The results indicate that pressure can not only improve the surface quality and refine columnar areas,but also eliminate the porosity to obtain the dense ingot. The average length of columnar grains obtained at applied pressure of 50 MPa is 20% shorter than that of the gravity alloy cast. The microstructure of the as-cast alloys mainly consists of primary α(Al),T2 and a small amount of AlLiSi and Al6(CuFe) phases. The applied pressure does not change the phase composition,but makes them smaller and more uniform. In addition,the microhardness,tensile strength and elongation of the alloy increase with increasing the pressure,but the applied pressure does not affect the mechanical properties obviously when the pressure exceeds 50 MPa. The T5 heat-treated alloy prepared under 50 MPa can reach a level of ultimate tensile strength of 329 MPa,elongation of 6% and microhardness of 135HBS,which are 7.2%,107% and 3%,respectively higher than those of the gravity cast alloy.
Key words: Al-Li-Cu alloy; squeeze casting; structure; mechanical property
