The relationship between TMT processing and microstructure in high strength 7075 Al alloys

摘要

The main objective of the present investigation is tostudy the effect of the thermomechanical treatment on thestructure-property relationships of 7075 plate. Particular emphasishas been placed on clarifying the origin of the anisotropy ofmechanical properties. It shows that the application ofthermomechanical treatment improves the microstructure andoverall tensile properties of 7075 plate. Grain size becomes finerand the morphology of coarse intermetallic particles becomefavorable as the 7075 plate is thermomechanically processed. Thisimprovement of microstructure directly influences the tensileproperties of 7075 plate. While the thermomechanically treated(TMT) 7075 plate don't show any significant change in tensileproperties with specimen orientation, there exists a large variationof tensile properties, in especially elongation, of heat treated (HT)7075 plate with specimen orientation. HT 7075 plate in LTorientation has a much lower elongation than that in L orientation.Detailed fractographic study reveals that poor ductility in LToriented specimen is due to the large effective grain size and alsodue to the occurrence of cleavage fracture of coarse intermetallicparticles along grain boundaries. In short, it has been found that theapplication of thermomechanical treatment improves the tensileproperties of 7075 plate and it can be directly applied for the alloyprocessing for forged parts.