STUDY OF THE NUCLEATION MECHANISM OF α-Al GRAINS AFTER ADDITION OF Al-Ti-B MASTER ALLOYS

1.IntroductionTheAl-Ti-BmasteralloyshavehadanincreasinglyimportantindustrialapplicationforthegrainrefinementofcommerciallypureAl,buttheprecisemechanismsarenotclearlyestablished.ThemechanismsofgrainrefinementbytheadditionofTiandBcanbemainlysummarizedasthe"peritecticreaction"theory1,2],"boride"theory3--5]and"duplex"nucleationmechanis.6].Detaileddiscussionofthesetheoriesisbeyondthescopeofthepresentpaper.Onlythemainviewpointsofthetheorieswillbedealtwithhere.CrossleyandMondolfo1]presentedth…