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向铝中添加锂既能降低合金的密度,又能提高弹性模量,因此铝-锂合金是-种性能比较理想的航空结构材料。美国、西欧国家和苏联积极发展铝-锂合金。铝-锂合金的研究历史已经很久了,早在20年代初期联邦德国就出售过铝-锂合金产品。1957年美国铝业公司第一个研制了添加1.2％Li的Al-Cu-Li系2020合金。2020合金与高强铝合金7075相比,强度相当,密度低、刚度高(分别降低3％和提高8％),1958年以后美国海军用该合金作Navy RA-5C侦察机主翼的上下蒙皮,代替7075合金,使该部分材料的重量减轻6％。但由于2020合金的韧性低,特别是缺口敏感性高,在生产工艺中还存在一些问题,所以1966年以后在飞机上没有被采用,1969年便停止了生产。60年代苏联也研制了类似2020合金的低密度、高刚度BA23合金及Al-Mg-Li系1420合金。我国对铝-锂系合金的研究起步比较晚,60年代研制了S141合金,对合金成分、加工工艺及热处理制度作了详细的研究,1985年进行了技术鉴定。作为现在研究目标的低密度、高刚度合金,要求此以前合金的密度低7％以上。因此,锂的添加量要比2020合金的1.2％多,必须添加2～3％。在解决熔铸和加工工艺方面问题的同时,必须提高韧性。
The addition of lithium to aluminum both reduces the density of the alloy and increases the modulus of elasticity. Therefore, the aluminum-lithium alloy is an aeronautical structural material with good performance. The United States, Western European countries and the Soviet Union are actively developing aluminum-lithium alloys. The history of aluminum-lithium alloys has been around for a long time. Aluminum-lithium alloy products were sold in the Federal Republic of Germany as early as the early 1920s. In 1957, Alcoa developed the first Al-Cu-Li series 2020 alloy with 1.2% Li. Compared with the high-strength aluminum alloy 7075, the 2020 alloy has the same strength, low density and high rigidity (3% and 8% respectively). After 1958, the U.S. Navy used this alloy as the upper and lower skin of the main wing of the Navy RA- Instead of 7075 alloy, this part of the material to reduce the weight of 6%. However, due to the low toughness of 2020 alloy, especially the gap sensitivity, there are still some problems in the production process, so after 1966 was not used on the plane, in 1969 they stopped production. In the 1960s, the Soviet Union also developed low density, high stiffness BA23 alloy and Al-Mg-Li system 1420 alloy similar to 2020 alloy. In our country, the study of aluminum-lithium alloy started relatively late. In the 1960s, S141 alloy was developed. The alloy composition, processing technology and heat treatment system were studied in detail. In 1985, the technology was identified. The low-density, high-stiffness alloys that are the subject of current research require that the density of the previous alloys be lower than 7%. Therefore, the addition of lithium is more than 1.2% of the alloy 2020, and 2% to 3% must be added. In solving the casting and processing problems at the same time, we must improve the toughness.