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[liyong,liu Junwei,Gao Wenliang,Dai Muhai,Yao Jing and Shu Xiaoyong.Study on Superplastic Gas Bulging Forming of LZ91 Mg-Li alloy sheet[J].Rare Metal Materials and Engineering,2022,51(8):2992~3000.]
Study on Superplastic Gas Bulging Forming of LZ91 Mg-Li alloy sheet
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Received:July 15, 2021  Revised:August 13, 2021
Key words: LZ91 Mg-Li alloy  superplasticity  superplastic gas bulging forming  gas bulging forming properties  microstructure
Foundation item:航空、航天基金及产学研项目(6141B090573);江西省教育厅科技项目(DA202101175);省部级重点实验室开放基金项目(EG201901449);江西省微观结构重点实验室开放基金项目(EJ201901430)
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liyong,liu Junwei,Gao Wenliang,Dai Muhai,Yao Jing and Shu Xiaoyong  
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      The superplasticity, gas bulging forming properties and microstructure of LZ91 Mg-Li alloy sheet were studied by hot tensile test, gas bulging forming experiment, metallographic analysis and scanning electron microscope observation. The results show that the rolled LZ91 alloy sheet exhibits excellent superplasticity: the elongation is up to 343.7% and the strain rate sensitivity index is 0.697 when the hot tensile temperature is 573 K and the strain rate is 0.001 s-1. Under the conditions of bulging temperature of 573 K and bulging pressure of 0.06 MPa, the sheet forming height is 51.14 mm and the height-diameter ratio is 1.279, which indicates that the Mg-Li alloy sheet has good superplastic forming potential. Dynamic recrystallization occurs in both hot tensile and superplastic gas bulging forming, it can effectively improve the plastic forming ability of the alloy. The typical superplastic cavities morphology at both tensile fracture and bulging fracture shows that the main deformation mechanism is grain boundary slip, and the main cause of superplastic failure is the growth and connection of the cavity.