▁uniform ▁manner . ▁In ▁the ▁latter , ▁the ▁changes ▁occur ▁heter ogene ously ▁and ▁specific ▁transformed ▁and ▁un transform ed ▁regions ▁may ▁be ▁identified . ▁Ab normal ▁or ▁dis continu ous ▁gra in ▁growth ▁is ▁character ised ▁by ▁a ▁subset ▁of ▁gra ins ▁growing ▁at ▁a ▁high ▁rate ▁and ▁at ▁the ▁exp ense ▁of ▁their ▁neighb ours ▁and ▁tends ▁to ▁result ▁in ▁a ▁micro structure ▁domin ated ▁by ▁a ▁few ▁very ▁large ▁gra ins . ▁In ▁order ▁for ▁this ▁to ▁occur ▁the ▁subset ▁of ▁gra ins ▁must ▁possess ▁some ▁advantage ▁over ▁their ▁compet itors ▁such ▁as ▁a ▁high ▁gra in ▁boundary ▁energy , ▁locally ▁high ▁gra in ▁boundary ▁mob ility , ▁fav ou rable ▁texture ▁or ▁lower ▁local ▁second - phase ▁particle ▁density . ▁ ▁Fact ors ▁h ind ering ▁growth ▁If ▁there ▁are ▁additional ▁factors ▁prevent ing ▁boundary ▁movement , ▁such ▁as ▁Z ener ▁pin ning ▁by ▁particles , ▁then ▁the ▁gra in ▁size ▁may ▁be ▁restricted ▁to ▁a ▁much ▁lower ▁value ▁than ▁might ▁otherwise ▁be ▁expected . ▁This ▁is ▁an ▁important ▁industrial ▁mechanism ▁in ▁prevent ing ▁the ▁soft ening ▁of ▁materials ▁at ▁high ▁temperature . ▁ ▁In hib ition ▁C ertain ▁materials ▁especially ▁ref ract ories ▁which ▁are ▁processed ▁at ▁high ▁temper atures ▁end ▁up ▁with ▁excess ively ▁large ▁gra in ▁size ▁and ▁poor ▁mechanical ▁properties ▁at ▁room ▁temperature . ▁To ▁mit ig ate ▁this ▁problem ▁in ▁a ▁common ▁s inter ing ▁procedure , ▁a ▁variety ▁of ▁dop ants ▁are ▁often ▁used ▁to ▁in hib it ▁gra in ▁growth . ▁