... Inc.ÆÀ1¼1=5boundaryisoneinwhich1in5ofthegrainboundaryatomsmatch,asshowninFig.2.8(c).Twinboundariesmayformwithincrystals.Suchboundarieslieacrossdeformationtwinplanes,asshowninFig.2.8(d).Notethattheatomsoneithersideofthetwinplanesaremirrorimages.Stackingfaultsmayalsobeformedwhentheperfectstackinginthecrystallinestackingsequenceisdisturbed,Figs2.8(e)and2.8(f).Thesemaybethoughtofastheabsenceofaplaneofatoms(intrinsicstackingfaults)ortheinsertionofrowsofatomsthatdisturbthearrangementofatoms(extrinsicstackingfaults).IntrinsicandextrinsicstackingfaultsareillustratedschematicallyinFigs2.8(e)and2.8(f),respectively.NotehowtheperfectABCABCstackingofatomsisdisturbedbytheinsertionorabsenceofrowsofatoms.2.3.4VolumeDefectsVolumedefectsareimperfectionssuchasvoids,bubble/gasentrapments,porosity,inclusions,precipitates,andcracks.Theymaybeintroducedintoasolidduringprocessingorfabricationprocesses.AnexampleofvolumedefectsispresentedinFig.2.9.ThisshowsMnSinclusionsinanA707steel.AnotherexampleofavolumedefectispresentedinFig.1.16(d).This ... picture of nucleation and growth presented above is gen-erally observed in most crystalline metallic materials. However, the rate of nucleation is generally enhanced by the presence of pre-existing ... model of grain growth may be developed by using an analogy of growing soap bubbles. We assume that the growth of the soap bubbles(analogous to grains) is driven primarily by the surface energy of...