Non-isothermal tensile tests during solidification of Al–Mg–Si–Cu alloys: Mechanical properties in relation to the phenomenon of hot tearing

Abstract

An original set-up has been used to study the mechanical properties of aluminium alloys in tension during solidification with a high cooling rate (70 K s À1 ). The mechanical behaviour of 6056 aluminium alloy with and without grain refiner has been investigated as well as that of mixtures between AA6056 and AA4047. The results show that the alloys exhibit a viscoplastic behaviour in the mushy state. A transition is observed between fracture in the mushy state and fracture in the solid state as a function of the displacement rate. This displacement rate at the transition depends on the cooling rate and on the composition of the alloy. The displacement before fracture is observed to be independent of displacement rate but to depend on the composition and on the solidification rate. Based on the observations a criterion for fracture in the mushy state is proposed. A simple rheological law describing the mechanical behaviour of the alloys is coupled to a finite element calculation giving the thermal field during the tensile test. This simulation is able to reproduce the mechanical response of the solidifying alloy during a non-isothermal test.

Predicting the constitutive behavior of semi-solids via a direct finite element simulation: application to AA5182

“…As presented in the introduction, the laws for semi-solid constitutive behavior can be divided into two general types-(a) a coupled approach in which the solid and the liquid have separate constitutive behavior [3,[15][16][17][18][19], and (b) a single approach in which the two phases are treated as a single medium with one constitutive law [9][10][11][12][13][14]. In both cases, these relationships have generally been difficult to validate experimentally.…”

“…Some researchers [9][10][11][12][13][14] proposed semi-solid constitutive models based on a modified creep law where the load carrying area is related to the fraction solid or to the proportion of grain boundaries covered by liquid films. Other researchers [3,[15][16][17][18][19] proposed two-phase models consisting of a porous solid skeleton saturated with liquid.…”

Tensile Deformation Behavior of Al-Cu 206 Cast Alloys near the Solidus Temperature

“…Above 3% liquid content, both alloys show the similar tensile properties although the fracture displacements are slightly different. It could be proposed that above this critical liquid content of ~3%, the fracture is ruled by liquid phase exhibiting similar characteristics for both alloys [8].…”

“…Several experimental set-ups have been recently developed [6] [7] [8]. However, a uniform temperature distribution profile within 5-6 mm along the specimen length should be obtained to ensure that the test is conducted with a minimum variation in liquid/solid contents.…”

A three-phase simulation of the effect of microstructural features on semi-solid tensile deformation

“…Thirdly, one must be able to link the strain to the accumulation of damage prior to failure. While a number of recent experimental studies have been designed to investigate these requirements [15][16][17][18][19][20][21][22][23][24], a comprehensive understanding linking microstructural features to semi-solid constitutive behavior is needed to improve hot tearing criteria.…”