3606

3409

كارشناسي ارشد

خوردگي و حفاظت از مواد

اصفهان : دانشگاه صنعتي اصفهان ، دانشكده مواد

1385

هشت ، 2،1،[II] ص: مصور ، جدول ، نمودار

ص. ع. به فارسي و انگليسي

فتح الله كريم زاده ، احمد ساعتچي

1/5/86

محمود منير واقفي ، عبدالمجيد جعفري

مهندسي مواد

ID3409

فارسي و انگليسي قابل رويت در نسخه ديجيتال

AbstractIn this study effect of GTAW process on the structure corrosion behavior and mechanicalproperties of Ti6Al4V alloy weldment was investigated and the corrosion behavior andmechanical property were improved using of preweld and postweld heat treatments For thispurpose thin sheets of Ti6Al4V alloy GTA welded where welding heat input was 350 J mm In order to study the effects of heat treatment on the weldment structure corrosion behaviorand mechanical properties a combination of stress relieving solution treatment and aging onthin sheets of this alloy was done The stress relieving and aging treatments were carried out at600 C and 540 C respectively for 1 h followed by air cooling The solution treatment wasperformed at 950 C for half an hour followed by water quenching Structural characteristicsand mechanical properties of weldment were studied by optical and scanning electronmicroscopy SEM X ray diffraction tension and hardness test The electrochemical behaviorof weldment was also studied in Ringer s solution using open circuit potential timemeasurements and tafel polarization Structural investigations reveal presence of coarseprimary grains plus discontinuous phase along the grain boundaries in the fusion zone FZ Furthermore there was no sharp interface between FZ and heat affected zone HAZ This case was attributed to epitaxial growth of grains in FZ from coarsened grains of nearheat affected zone NHAZ This structure caused decreasing of corrosion resistance andelongation of weldment The results of investigations showed that size and shape of columnar grains do not tailor by any heat treatment below transformation temperature T Heattreatment used to improvement of corrosion behavior The results of corrosion tests showedthat solution treatment and aging after welding improve corrosion behavior of weldment andno preferential attack was not observed between base metal BM FZ and HAZ Thisphenomenon was attributed to formation of from martensite and from metastable andalso coarsening of plates during heat treatment Furthermore low temperature postweld heattreatments like stress relieving and also preweld heat treatments did not have any appreciableeffect in improving the corrosion behavior of weldment The results showed that weld ductilityof as welded sample 100 improved and hardness of diffrent zones was uniformed bysubjecting it to a solutionizing and aging treatment

فتح الله كريم زاده ، احمد ساعتچي

محمود منير واقفي ، عبدالمجيد جعفري