| Al-Mg alloy is widely used in shipbuilding and aerospace fields due to its high strength,high plasticity,light weight and easy processing.However,due to its serious intergranular corrosion problem of long-term service,it leads to its failure.Based on the research idea of grain boundary engineering,this paper focuses on the relationship between grain boundary structure and properties.Taking Al-Mg alloy as the research material,the quantitative characterization method of grain boundary interface matching based on electron backscatter diffraction and five-parameter analysis method is used to study the effects of pre-deformation temperature,pre-recovery time and different grain sizes on the proportion of { 111 } / { 1 11 } near singular boundaries in Al-Mg alloy.The main research results are as follows :(1)The pre-deformation temperature has a significant effect on the formation of { 111 }/ { 111 } near singular boundaries in Al-Mg alloy.The sample after solution treatment was subjected to unidirectional rolling at 180 ～ 300 ℃(thickness reduction of 80 %),and then immediately subjected to recrystallization annealing at 380 ℃ / 20 min.It was found that with the increase of pre-deformation rolling temperature,the proportion of { 111 } / { 111 } near singular boundaries of Al-Mg alloy increased first and then decreased,and reached a maximum of 6.18 % at 210 ℃ pre-rolling.With the increase of pre-deformation temperature,the recrystallization mode changes from discontinuous recrystallization to continuous recrystallization and then to discontinuous recrystallization.Compared with discontinuous recrystallization and dynamic recrystallization,continuous recrystallization behavior is more conducive to the formation of { 111 } / { 111 } near singular boundaries in Al-Mg alloy.(2)The pre-recovery time has a significant effect on the formation of { 111 } / { 111 }near singular boundaries in Al-Mg alloy.The Al-Mg alloy samples with homogeneous microstructure after solution treatment were rolled at 210 ℃,pre-recovery at 210 ℃ for 30 min,1 h and 2 h,and then annealed at 380 ℃ / 20 min.It is found that with the extension of prerecovery time,the proportion of { 111 } / { 111 } near singular boundaries increases first and then decreases.Among them,the proportion of { 111 } / { 111 } near singular boundaries reaches a maximum of 5.07 % at 1 h of pre-recovery,and a minimum of 3.95 % at 30 min of pre-recovery.The analysis shows that the overall pre-recovery is unfavorable to the continuous recrystallization behavior,but the { 1 1 0 } / / ND texture appears at 1 h of pre-recovery,which has a favorable effect on the formation of { 111 } / { 111 } near singular boundaries.(3)The initial grain size has a significant effect on the formation of { 111 } / { 111 }near singular boundaries in Al-Mg alloys.The Al-Mg alloy samples with initial grain size of 150 μm and 15 μm were rolled at 210 ℃ and annealed at 380 ℃ / 20 min.The proportion of{ 111 } / { 111 } near singular boundaries in the Al-Mg alloy sample with an initial grain size of 15 μm is 5.59 %,while that of the 150 μm sample is only 3.91 %.The analysis shows that the samples with smaller initial grain size have more grain boundaries in the unit area,and the samples with more original grain boundaries have larger deformation substructure density on both sides of the grain boundary after deformation,and the microstructure evolution during subsequent recrystallization annealing is mainly continuous recrystallization.(4)The off-line in-situ corrosion experiment shows that the corrosion resistance of { 111 } / { 111 } near singular boundary of Al-Mg alloy is between coherent twin boundary and general high angle boundary.The grain boundary characteristics depend largely on the grain boundary structure and characteristics.The { 111 } / { 111 } near singular boundary structure is simulated by O lattice calculation.It is found that the atomic arrangement shows a certain period,which makes the near singular boundary have low energy stability. |
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