摘要
This article concentrates on the investigation of hot deformation behavior of conventionally rolled commercial grade AA5083 alloy( Al-4. 5Mg),for automotive and aviation applications. The superplastic response of the alloy was investigated at high strain rates( ≥10- 3s- 1),and a temperature range of 400 ℃ to 550 ℃. An elongation to failure of 201% was achieved at low temperature( 425 ℃) and high strain rate( 10- 2s- 1),which indicates sufficient ductility under hot deformation for manufacturing of extremely complex shapes using superplastic forming technology. Furthermore,the alloy exhibited a maximum elongation of about 470% at strain rate of 10- 3s- 1and a temperature of 525 ℃. The deformation and failure mechanisms at both the critical conditions were studied as a function of strain rate and temperature. The contributions of strain-rate sensitivity and strain hardening were analyzed in relation to the observed tensile ductilities. Deformation mechanism of the alloy was also investigated with reference to Strain rate sensitivity index( m) and Activation energy( Q) for the given test condition. Empirical calculations reveal that dominant deformation mechanism responsible for hot deformation of the alloy is grain boundary sliding( GBS),which is further supported by deformed surface examination using scanning electron microscopy( SEM). Fracture surfaces of the samples deformed to failure,at relatively higher and lower strain rates,was examined to investigate the micromechanisms governing failure. Phenomenon of cavity nucleation,growth and coalescence was observed to be the failure mechanism in the investigated alloy.
This article concentrates on the investigation of hot deformation behavior of conventionally rolled commercial grade AA5083 alloy （A1-4. 5Mg）, for automotive and aviation applications. The superplastic response of the alloy was investigated at high strain rates （ 1〉10-3 s-I） , and a temperature range of 400℃to 550 ℃. An elongation to failure of 201% was achieved at low temperature （425 ℃ ） and high strain rate （ 10-2s-1 ）, which indicates sufficient ductility under hot deformation for manufacturing of extremely complex shapes using superplastic forming technology. Furthermore, the alloy exhibited a maximum elongation of about 470% at strain rate of 10-3s-1 and a temperature of 525℃. The deformation and failure mechanisms at both the critical conditions were studied as a function of strain rate and temperature. The contributions of strain-rate sensitivity and strain hardening were analyzed in relation to the observed tensile ductilities. Deformation mechanism of the alloy was also investigated with reference to Strain rate sensitivity index （m） and Activation energy （Q） for the given test condition. Empirical calculations reveal that dominant deformation mechanism responsible for hot deformation of the alloy is grain boundary sliding （ GBS）, which is further supported by deformed surface examination using scanning electron microscopy （SEM）. Fracture surfaces of the samples deformed to failure, at relatively higher and lower strain rates, was examined to investigate the micro- mechanisms governing failure. Phenomenon of cavity nucleation, growth and coalescence was observed to be the failure mechanism in the investigated alloy.
基金
Sponsored by the National Science and Technology Major Project(Grant No.2010ZX04014-073-01)
