Effect of plastic anisotropy and Portevin-Le Chatelier bands on hole-expansion in AA7075 sheets in -T6 and -W tempers

Numerical prediction of sheared edge profiles in sheet metal trimming using ductile fracture modeling

Microstructure and properties research of Al-Zn-Mg-Cu alloy with high strength and high elongation fabricated by wire arc additive manufacturing

Owing to the notorious hot-crack susceptibility and severe softening fusion-weld joints of Al–Zn–Mg–Cu alloys, they are generally considered unweldable. In this study, TiC/7xxx (TC) and TiC–TiB2/7xxx (BC) aluminum matrix composites, fabricated by in-situ mixed-salt reaction, were used as filler rods of spray formed 7055 alloys to modify the microstructure and mechanical properties of TIG weld joints. Compared with 7055-weld metal (WM), the grain sizes of TC-WM and BC-WM were refined from 100 μm to 24 μm and 26 μm, respectively. The precipitation of eutectic phases in WM was reduced by ceramic particles, which decreased the hot-crack susceptibility of joints. In the as-welded state, the ultimate tensile strength of TC and BC joints increased from 240 ± 5 MPa to 274 ± 5 MPa and 300 ± 5 MPa, respectively. The addition of ceramic particles also improved the impact toughness and hardness of weld joints. Grain refinement, load-bearing strengthening, coefficients of thermal expansion mismatch strengthening, and Zener pinning strengthening are the dominant strengthening mechanisms of weld joints with ceramic particles.

Effect of TiC/TiC–TiB2 on microstructure and mechanical properties of spray formed 7055 aluminum alloy TIG welded joints

In this work, a novel ultrahigh-strength Al−10Zn−3.5Mg−1.5Cu alloy was fabricated by powder metallurgy followed by hot extrusion. Investigations on microstructural evolution and mechanical properties of the fabricated samples were carried out. The results show that the grain size of sintered samples matches with the powder particles after ball milling. The relative densities of sintered and hot extruded samples reach 99.1% and 100%, respectively. Owing to the comprehensive mechanism of grain refinement, aging and dispersion strengthening, the ultimate tensile strength, yield strength and elongation of the Al−10Zn−3.5Mg−1.5Cu alloy after hot extrusion and subsequent heat treatment achieve 810 MPa, 770 MPa and 8%, respectively.

Microstructural evolution and mechanical properties of an ultrahigh-strength Al−Zn−Mg−Cu alloy via powder metallurgy and hot extrusion

Mechanical properties of solution heat treated Al-Zn-Mg-Cu (7075) alloy under different cooling conditions: Analysis with full field measurement and finite element modeling

Metal forming or shaping processes, such as sheet metal forming and bulk forming, are widely used in many industries including automotive industry. Before computational simulations were widely used in the field of metal forming industry, the trial-and-error based empirical approach was conventionally applied to the optimization of the metal forming process and product. The most commonly employed numerical approach in the metal forming process for robust process optimization is the finite element analysis. Friction, one of the parameters that significantly affect the accuracy of numerical analysis, depends on several variants such as surface quality, contact pressure, lubrication, deformation, and the forming environment. Despite the complexity and difficulty of identifying friction mechanisms, accurate friction models are essential and hence have been proposed by numerous researchers. In this paper, the friction models in the previous studies are reviewed by categorizing them into the boundary lubrication condition and mixed-boundary lubrication condition according to their evaluative influences on friction. Since friction models have been proposed based on the contact theories, an overview on the contact models is also included in this paper. In addition, the contribution of several parameters on the friction such as surface roughness and material properties of the tool, adhesion, contact pressure, sliding speed, bulk deformation is also discussed. This review paper aims to provide an understanding and insight into the friction modeling and simulation along with associated friction experiments.

Chanmi Moon

Papers

Mechanical properties of solution heat treated Al-Zn-Mg-Cu (7075) alloy under different cooling conditions: Analysis with full field measurement and finite element modeling

A Review on Friction and Lubrication in Automotive Metal Forming: Experiment and Modeling