.1420 Aluminum Lithium Alloy Heat Treatment Process And Organizational Performance

The effect of different heat treatment on the macroscopic properties (age- hardening character, tensile properties and anisotropy)and microstructure of two 1420 Al-Li alloy sheets were systematically studied in this paper. By means of heat treatment, hardness test, tensile test, OM (optical microscope) and SEM observation, and TEM analysis, the main conclusions can be summarized as follows:1. At 120 ℃artificial ageing, the suitable ageing time of peak properties(strength and hardness) of 1420 alloys is about 8-12h. In order to get the optimum combination of strength and ductility, the reasonable ageing time of 1420 Al-Li alloys is about 8~16h.2. By means of the several kinds of appropriate heat treatment, the mechanical properties of 1420-105# and 117# Al-Li alloys can meet or even exceed the demand of expected value: δb≤410MPa, δ2≤255Mpa, σ≤6%.3. Through the same quenching treatment, the strength( σ b, σ 0.2) of the tensile specimens of two 1420 alloys is better under the condition of double ageing than single ageing at the aging time point 8h. Otherwise, the result is reverse. Generallyspeaking, 8 is higher when double ageing is taken.4. As far as the tensile specimens sampled along rolling direction are concerned, the strength of 1420 alloy is higher under the air-quenching than that ofwater-quenching, if they are treated with the same ageing.5. The anisotropy of the 1420 alloy sheets-105# and 117# is obvious: In transverse(90° ) direction, the strength is the highest while 6 is better than some direction; in 45° direction, the strength is the lowest and δ is the best; in rolling(0°) direction, $.2 is better, but $b and 8 are not good enough.6. The major strengthening phase of 1420 alloy is δ '(Al3Li) phase; 1420 alloy sheets' microstmcture in various direction is different, generally speaking , it is a mixed microstructure composed of deformed grains (fibrillation) and recrystallized grains. Although there are some intergranular fracture and cracks in a few specimens fractures, the basic fracture character of 1420 alloys static tensile specimens is transcrystalline plastic fracture. The fracture character is also anisotropic.