AdiffusioncoupleofweldedAandBwasgivenadiffusionannealatelevatedtemperatureandthencooledtoroomtemperature.Chemicalanalysisofthesuccessivelayercutparalleltotheweldinterfaceshowthatoveradistanceof5000nm,NAchangedfrom0.3to0.35.Assumethatthenumberofatomsperm3ofbothpuremetalsis9×1028.a)determinetheconcentrationgradientdnA/dx,b)ifthediffusioncoefficientatthepointinquestionatannealingtemperaturewas2×10-14m2/s,determinethenumberofAatomspersecondthatwouldpassthroughthiscross-sectionattheannealingtemperature.Neglecttheinterfacemotion.
