【作者】 张亮； 张小龙； 吴国华；

【Author】 ZHANG Liang;ZHANG Xiao-long;WU Guo-hua;Shanghai Jiao Tong University, National Engineering Research Center of Light Alloy Net Forming;

【机构】 上海交通大学轻合金精密成型国家工程研究中心；

【摘要】 Al-Li合金具有低密度、高比强度、高比刚度和良好的耐蚀性,在航空航天领域具有广阔的应用前景。但是,目前国内外研究和应用的Al-Li合金主要集中于变形合金,在铸造Al-Li合金研究开发方面还处于起步阶段。合金化和热处理是控制铸造Al-Li合金强韧性的主要手段,本文通过硬度测试、拉伸试验、SEM以及TEM等方法系统研究了Mg元素的添加（0, 0.5, 1和1.5 wt.%）对铸造Al-2Li-2Cu-0.2Zr合金微观组织和力学性能的影响。结果表明,合金铸态组织晶界附近富集非平衡第二相,通过双级固溶处理第二相能很好的溶入基体;Mg元素对合金铸态组织晶粒尺寸无明显影响。Mg的添加对合金的力学性能有显著的提升作用,综合力学性能最好的含0.5wt.%Mg合金,相比于基合金屈服强度提升了近100MPa。硬度测试表明Mg添加提高了时效硬化效果,缩短了到达峰时效的时间。合金强韧性变化的主要原因是,Mg的添加抑制了θ′（Al₂Cu）相的析出,引入了S′（Al₂CuMg）相并促进T₁（Al₂CuLi）相的均匀析出,从而使合金力学性能得到提高。Al-2Li-2Cu-0.2Zr-0.5Mg合金经固溶时效处理后（460℃×32 h+520℃×24 h固溶处理,175℃时效32 h）,抗拉强度达到443 MPa,屈服强度达到366MPa,延伸率达到4.5%。更多还原

【Abstract】 Al-Li based alloys own considerable applications in aerospace field due to its impressive combination of low density, enhanced specific strength, high stiffness to weight ratio and good corrosion resistance. The existing researches and applications of Al-Li alloys are mainly wrought alloys while researches dedicated on cast Al-Li alloys designing are still in the initial stage. Certain alloying additions and optimal heat treatments are mainly approaches to control the optional strength and toughness of cast Al-Li alloys. Effect of Mg content（0, 0.5, 1 and 1.5 wt. %） on microstructure and mechanical properties of cast Al-2 Li-2 Cu-0.2 Zr alloy was investigated by means of macro hardness test, tensile test SEM and TEM observations. The results indicated that a population of secondary phases enriched along grain boundaries in as-cast studied alloy, most of which dissolved into the α-Al matrix after solution treatment. No appreciable refinement of as-cast alloy was observed due to Mg addition. Profound enhancement in mechanical properties of the studied alloy was obtained after T6 heat treatment and the best mechanical properties were obtained in alloy with 0.5 wt. % Mg addition. 0.5 wt. % Mg addition profoundly increases the yield strength of the baseline alloy by nearly 100 MPa, indicating the prominent strengthening effect of minor Mg addition in cast Al-Li alloys. Macro hardness tests revealed that Mg enhanced the ageing response and shortened the time to peak. TEM observations revealed that θ′（Al₂Cu） was suppressed and S′（Al₂Cu Mg） was introduced with minor Mg addition and accelerated precipitation of T1（Al₂CuLi） phases was simultaneously observed. When subjected to a two-stage solution heat treatment（460 ℃ ×32 h+520 ℃ ×24 h） followed by ageing for 32 h at 175°C, a good combination of strength and ductility with ultimate tensile strength（UTS） =443 MPa, yield strength（YS） =366 MPa and elongation（EL） =4.5% could be obtained in cast Al-Li-Cu alloy with 0.5 wt. % Mg addition.更多还原