The Effect of Applied Forging Pressure on Primary Structure Deformation in Rheology Forging Process With Solid Fraction Controlled A356 and AA2024 Alloys

Abstract

Mechanical properties and microstructure of heat-treated samples of A356 and AA2024 aluminum alloys, which were rheoforged by varying the change in pressure and temperature were investigated, preventing defects such as porosity, liquid segregation, and insufficient filling occurring during rheoforging process. The rheology material was fabricated by an electromagnetic stirring process by controlling stirring current so that shearing force and temperature of the molten metal were controlled during electromagnetic stirring. As a result, by crushing dendrite and rosette type microstructures, fine and globularized rheology material was obtained and the feasibility of the rheoforging process was found to be positive. In the case of the direct rheoforging process, excessive applied forging-pressure caused material spattering, which in turn caused eutectic segregation. This segregation brought about a shrink hole and thus led to a deterioration of mechanical strength. According to varied applied forging pressures, agglomeration phenomena of primary particles of wrought aluminum alloy remarkably increased as compared with an as-cast aluminum alloy.

Rheological transitions in semi-solid alloys: In-situ imaging and LBM-DEM simulations

“…1a. 16 shear deformation experiments were conducted on semi-solid samples that had average grain size ̅ less than 200 µm (with 500 -2000 grains in the FOV), with a range of initial volumetric solid fractions between 0 = 44% -85%, and a range of constant push plate displacement rates from / = 1 -2800 m•s -1 (corresponding to global shear rates on the order 10 -4 -10 -1 s -1 ).…”

“…Examples include high-pressure die casting [1][2][3][4], twin-roll casting [5][6][7], and the soft reduction in the continuous casting of steel [8,9]. However, their use is often limited by semi-solid deformation-induced casting defects such as macrosegregation [6,[10][11][12][13][14][15][16], and shear cracking [11,17]. To optimize these processes and gain better control of these defects, a deeper understanding of semi-solid alloy deformation is required.…”