STUDY IN FO RMATION OF SUB GRAINS AND MICROCRACKS IN WEIDED METAIS UNDER FATIGUE LOAD

With TEM( Transmission Electron Microscope) ,ithasobserved and analyzedthatforming processof Sub grainsand position offormingfatigue microcracksarein Welded metalsofthe16 Mnsteelundertensile tensilestress. Theresultsindicatedthattheforming processof Sub grainsfrom dislocationtanglecellstotheSub grains. Thepositionofformingfatigue micro crackisattheoxidativeinterfaceand granular noncrgstallines and Sub boundaries. Thece mentiteineutectoidsafterfracture may beproduced microcracks.