Study On The Heat-treatment Of Homogenization, RRA And Residual Stress Of Plate Of Al-8.0Zn-2.1Mg-2.3Cu Aluminum Alloy

The purpose of this paper is to study the effects of the solution and aging treatment on microstructure and properties of7055ultra-high aluminum alloy. The methods used in the experiments contain measuring the mechanical property, conductivity, and observing microstructure by using TEM, SEM, DSC and metallographic analysis. The materials used for the experiment contain7055ultra-high aluminum alloy Φ200mm as-cast ingot,7055thick hot-rolled plate and7055thick pre-drawing plate. The aim of this paper is to establish a foundation for optimizing the homogenization process which the strength of alloy can be improved and determination the residual stress.The main results are as follows:1. There are many layered η(MgZn2) phase in the Φ200mm as-cast ingot. The melting point of η(MgZn2) phase is478℃.2. The η(MgZn2) phase of Φ200mm ingot as-cast can soluble to mztrix when homogenized to470℃for24h., but not completely.3. There many η(MgZn2) phase, and Al7Cu2Fe phase in25mm hot-rolled plates. The melting point of η(MgZn2) phase is478℃. The η(MgZn2) phase of Φ200mm hot-rolled plates can soluble to mztrix when solution to470℃for2h., but the Al7Cu2Fe phase not change.4. The size of25mm hot-rolled plates not increased with increasing solution treatment time. The best process of solution is solution at470℃×30(min-60min).5. Being pretreatments before solution let the size of25mm hot-rolled plates grain size not changed with the increase of solution time, but the dispersed phase more smaller. Pretreatment at different temperatures for different times on the strength of hot-rolled plates has no effect, but the conductivity is the highest for430℃×2h, the elongation is the best with no decreasing intensity for430℃×2h.6.25mm thick plate longitudinal residual stress larger than horizontal residual stress. After quenching the pre-stretching, the longitudinal quenching stress can eliminate86%. After120℃×7h+165℃×13h two-step aging the longitudinal quenching stress can eliminate90%. Hot-rolled plates bre quenching in the laboratory, after120℃×7h+165℃×13h two-step aging the longitudinal quenching stress can eliminate32%.7. The quenched residual stress of7055aluminum alloy plate in the direction of the distribution is uneven. In the thickness direction of cutting the right location, the plate is not deformed.8. In the direction of the plate thickness about3.5mm below the surface, the plate of25mm and60mm thick7055alloy quenched pre-stretching quenching residual stress is maximum.