Research On Pre-stretching And Hardenability Of Aluminium Alloy Thick-plate

While the techniques of integrated thick plate machining are coming out, Aluminum alloy thick plates have broadly been used in space and transportation industry as framework profiled material instead of former riveted and forging parts due to its excellent properties, Therefore, the market demands of thick plates increase sharply, However, serious residual stress will be introduced by quenching in water after solution treatment, which leads to heterogeneous distribution of mechanical properties along thickness, as well as dimensional effect during subsequent machining. The proposed method of pre-stretching is one of the most typically effective technologies to eliminate residual stress, that means pre-strain from 1% to 3% will be applied to quenched plate before ageing process.The objective of this study was to investigate the distribution difference of mechanical properties through section thickness. selected tensile test, hardness test, microstructure analysis and Jominy hardenability tests have been performed in some kinds of alloys in common use to evaluate the influence of quench's temperature on mechanical properties and relationship between cooling rate and quenching structure. at last, the depth of hardenability of alloy2024 and 6082 were obtained.The mechanical properties of aging hardenable Al alloy vary with aging time, in order to ensure quality of stretching plate, and avoid over-stretching or insufficient-stretching, mathematical model of stress, plastic strain and aging time has been proposed for real time operation.Meanwhile, to analysis the pre-stretching process visually, elastic-plastic finite element method was conducted with software ANSYS to simulate the tensile process. the result of equivalent stress and strain contours was obtained, it is clear that the values of plastic strain distribution vary throughout the plate, and that plastic strain close to clamped zone is uneven and small, whereas strain distribution far from clamped zone is uniform. The size of transition zone in between even and uneven deformation was gained. In addition, the amount of plastic strain imposed by external force decides the degree of residual stress release, so it's easy to identify unqualified area where plastic strain is less than 1% according to distribution law of plastic strain , this area should be cut off as scrap.