TY  - EJOU
AU  - Yang, Ping 
AU  - Cai, Wei 
AU  - Zhao, Pengyang 

TI  - Microscopic	Mechanism	of	Void	Nucleation	at	Dislocation	Boundaries: A	 Discrete	Dislocation	Dynamics	Simulation	Study
T2  - The International Conference on Computational \& Experimental Engineering and Sciences

PY  - 2023
VL  - 26
IS  - 1
SN  - 1933-2815

AB  - Void	nucleation	is	of	great	significance	in	understanding	ductile	 fracture	of	many	important	engineering	
materials.	 Recent	 experiments	 have	 shown	 that	 voids	 are	 nucleated	 via	 vacancy	 condensation	 and	
dislocation	boundaries	are	the	main	nucleation	sites.	However,	it	is	still	unclear	what	role	is	played	exactly	
by	dislocation	boundaries	in	promoting	void	nucleation	and	what	kind	of	defect	configuration	is	involved.	
Here	 we	 propose	 a	 new	 mechanism	 for	 dislocation	 boundary-induced	 void	 nucleation	 and	 develop	
accordingly	a	vacancy	condensation	model	based	on	the	classical	nucleation	theory.	The	model	suggests	that	
vacancy	 condensation	 to	 form	 void	is	impossible in	 the	 absence	 of	 external	 driving	 force	 and	 there	is	 a	
nonlinear	negative	correlation	between	the	activation	free	energy	barrier	for	void	nucleation	and	the	local	
hydrostatic	tensile	stress.	It	is	also	shown	that	the	relaxation	of	elastic	strain	energy	of vacancies,	absent	in	
the	previous	void	nucleation	models	and	introduced	in	ours,	can	greatly	lower	the	activation	energy	barrier	
and	 thus	 cannot	 be	 ignored. The	 kinetic	 feasibility	 of	 the	 newly	 proposed	 mechanism	 is	 examined	 and	
explored	using	three-dimensional	discrete	dislocation	dynamics	simulations.	Our	simulation	results	show	
that	vacancy	condensation	occurs	more	likely	near	the	dislocation	boundary	than	in	the	dislocation	cell	and	
the	synergy	of	multiple dislocation	pile-ups	is	 the	key	 to	enabling	dislocation	boundaries	 to	serve	as	 the	
preferential	sites	for	void	nucleation,	which	cannot	be	achieved	by	a	single	dislocation	pile-up	alone.
KW  - 

DO  - 10.32604/icces.2023.010400