Impurity-induced vacancy clustering in cold-worked nickel

Defects in Some Hydrogenated Metallic Materials Studied by Positrons

“…For al l sam pl es two m ai n sta ges of recovery can b e di sti ngui shed. Thei r tem p erature ra nges correl ate wi th tho se observed i n deform ed Ni [11]. At the Ùrst sta ge the beha vi our of § a v and S i n D H and HD sampl esi s pra cti cal l y sim i l ar i rrespecti ve to the sequence of The results of PL T spectra ana l ysi s are pl otted i n Fi g. 3.…”

“…Acco rdi ng to theo reti cal cal cul ati ons [12 ], PL T of 250 ps corresp onds to the clusters consisti ng of 4 vacanci es, whi le PL T of 350 ps observed i n hydro genated sam pl esi s p eculiar to aggl om erati on of more tha n 10 vacancies. Ab o ve 370 K va canci es in Ni get m ovable [11] and enabl e clusters to gro w i ncorp ora ti ng singl e vacanci es or pro vi di ng pro cesso f coal escence. Ab ove 500 K cl usters sta rt to di ssociate, and vacanci es start to m i gra te to the sinks.…”

Positron annihilation spectroscopy of vacancy-type defects hierarchy in submicrocrystalline nickel during annealing

“…1(b)). The component of positron lifetime spectra 3 ~ 230-290 ps demonstrates the trap of positrons at defects that have a larger free volume in comparison to single vacancies and dislocations [3][4][5]. Following [3][4][5], the value of the component 3 ~ 230-290 ps is considered to be typical for vacancy clusters.…”

Positron annihilation at grain boundaries in metals

“…[12]) and is slightly lower than the measured bulk lifetime of Ni (108 ps [13]). The same applies to the single vacancy in Ni (measured lifetime 180 ps [14]). …”