Study on the experimental and molecular dynamics simulation of laser shock dynamic compaction of Nano-aluminum powder

This study elucidates the laser shock dynamic compaction (LSDC) mechanism of Nano-aluminum powder and its influence on changes in crystal defects at the atomic scale. The molecular dynamics method was utilized to simulate the LSDC and develop a model for the compaction of Nano-aluminum powder. An independently designed LSDC device was employed to examine the effects of Quasi-Steady Compaction (QSC) and QSC + LSDC on the relative densities of Nano-aluminum compacted billets under varying loads. The experimental results revealed that the QSC + LSDC composite process yielded compacted billets with a relative density of 97.8 %, which was 15 % higher than that of the compacted billets prepared under the QSC process. Post-LSDC composite compaction, the compacted billets exhibited a maximum hardness of 103.56 HV, an increase of 26.59 HV compared to that achieved under the QSC process. The average grain size in the compacted billet was reduced from 67.2 nm to 54.7 nm, indicating grain refinement. Molecular dynamics simulations showed that during the LSDC, the Nano-aluminum compacted billets transitioned from a face-centered cubic to a hexagonal close-packed structure. The LSDC process was predominantly characterized by 1/6(112)Shockley dislocations, constituting approximately 76.47 %, whereas 1/3(111)Frank dislocations were minimally present, accounting for approximately 0.31 %. Activating slip surfaces by moving incomplete Shockley dislocations with Burgers vectors of 1/6 [2 -11] and 1/6[- 11 -2] led to the formation of laminar dislocations.