Effects Of Large Strain Deformation On Microstructure Of The Aluminum Alloy Ingot

Large deformation processing is an effective way to significantly improve the microstructure and properties of the aluminum alloy ingot. Equal-Channel Angular Pressing （ECAP） is an important large deformation technology. This dissertation mainly focuses on large deformation processing of aluminum alloy ingot.The research work and results as follows:1. Effect of equal channel angular pressing on microstructure of 6063 Al fabricated by in-situ alloying in electrolytic Al liquid was investigated. The results show that the ECAP processing can effectively distribute the un-electrolytic, nano-scale and aggregated Al₂O₃ inclusions presented on the grain surface, and can refined AlFeSi inclusions of the alloy considerably, with the size variation from 5-15μm length/1-2μm width to 1-3μm length/1-2μm width. In addition to the refinement, the ECAP processing also improved significantly the distribution of the AlFeSi inclusions, alloy density and corrosion-resistance, and introduced high density of dislocations leading to a-60% increase of hardness. Relative to the equivalent strain of about 0.5 ECAP processing, the equivalent strain of about 0.9 ECAP processing can more effectively enhance the aluminum alloys, but it cannot significantly further increase the hardness.2. Equal channel angular pressing （ECAP） of 7085A1 alloy ingot has been performed. It is found that the ingot can be ECAP processed with an imposed equivalent strain of-0.5 single pass. The key is to take of the preheating temperature （500℃） of the ingot. ECAP processing significantly improved the microstructure of 7085 aluminum alloy ingot. The porosity is laminated, The inclusions （AlFeCu, etc.） are fragmented and distributed away. High density of dislocations is introduced into the alloy, which provided a powerful driving force for the recrystallization to refine grain in the following solution heat treatment. It is also found that ECAP processing plus solid solution aging treatment is an effective approach to produce fine grain （10-30μm） and high hardness 7085 aluminum alloy. Besides, three-stage solution treatment （470℃/2h +480℃/2h+490℃/2h） was better than single-stage solution treatment（470℃/2h）,in which grain growth has not has found to occur.3. Hot compressin large strain deformation of large-scale 7085Al alloy ingot with Strontium micro-alloying was studied. The result indicates that micro-alloying can significantly refine the aluminum alloy ingot. The Deformation processing can make the alloy fully dense, but its effect on fragmenting of inclusions was not as effective as ECAP technology.There are few reports both at home and abroad related to the research presented in this dissertation. The prenent research methods and results provide preliminary foundation for improve of microstructure and properties of aluminum alloy ingot.