Heterogeneous nucleation in solidifying metals

✍ Scribed by R.T. Solthin; G.A. Chadwick

• Publisher: Elsevier Science
• Year: 1978
• Weight: 861 KB
• Volume: 26
• Category: Article
• ISSN: 0001-6160
• DOI: 10.1016/0001-6160(78)90122-0

✦ Synopsis

Hetzrogwzous nucleation experiments hate been carried out using xl!oy droplets concain& in a nncleant matrix. These specimens were made using a simple casting tend annealing trrstmcnt of selected alloys. Thermal anal+ was used to detect the nucleation in the alloy droplets. The results obtained show that this method was capable of givin g reproducibis undercooling results which in most cases were much larger than had been xhizved by the use of other techniques. Some r-suits tvere, in fact, greater than those previously aa\*' Li&pted as being close to homogeneous l?LICk~t~Oil. .kni)Sir of these results gave no support to the non-rxiprocal nuclitation theor>-or the electrostatic s&a put forward by other workers. Nucleation at small undercoolings was found only in those couples whose crystal structure and bonding were similar, but these factors were considered to be insurficient in themselves for eficacious heterogeneous nucleation. A relationship betxssn the melt+ point of a substrate and its putencl; as a nuclsant was ~1s~ found for some materi&. R&m&--On a effect& des expkriences de germination httbrorZne B I'aide dc goutielzttes ;I';lll;3ss contenues dans unr matrice germinarrice. Les ichantiilons a'~a:ent Srt pripar~~-se dc ces resuitats n':~ pr:s donni d'arguments en faveur de la theorie de la germination non&ciproque ou de I'e!?et Clectrostatiq:ie avan& par d'autres autrurs, On n'a obtenu de germination pour une faible surfusion yue dans ies couples de mttaux dont la structure cristalline et is type de liaison Ctaient sembfables, mnis on a consid&! que ces facteurs etaient insuffisants par eux-mkmes pour une germination h&&rog+ne e&ace. On a kgalement trouve pour certains matCriaus une relation entre le point de fusion d'un support et son efficacit6 comme prminateui.~~