Haddad Sabzevar M., Fredriksson H.,
Volume 3, Issue 1 (Oct 2006)
Abstract
The hot cracking susceptibility can be determined by establishing the transition temperature between brittle and ductile fracture at high temperature tensile testing of in situ solidified samples. High temperature tensile properties were determined for commercial cathodic pure Cu and Cu- 30%Zn alloy. The transition temperatures for pure Cu and Cu-30%Zn were evaluated from ultimate tensile stress, true strain and area reduction at different testing temperatures. The results show that hot cracking in pure Cu also occurred below and near to its melting temperature. It can be proposed that in this case excess vacancies and vacancy diffusion and condensation are the dominating mechanisms for hot crack formation. The transition temperature for Cu- 30%Zn was much lower than its solidus temperature and this alloy has more susceptibility to hot cracking as compared to pure Cu. The effect of two different cooling rates (15 °C/min and 60 °C/min) on the transition temperature was investigated. The results show that by increasing cooling rate, the transition temperature will increase. The morphology of fracture surfaces for both ductile and brittle modes were evaluated by SEM Two different morphologies, i.e. interdendiritic and intergranual fracture, was found.
M.h. Avazkonandeh-Gharavo, M. . Haddad-Sabzevar, H. Fredriksson,
Volume 13, Issue 2 (June 2016)
Abstract
Because the partition coefficient is one of the most important parameters affecting microsegregation, the aim of this research is to experimentally analyse the partition coefficient in Al-Mg alloys. In order to experimentally measure the partition coefficient, a series of quenching experiments during solidification were carried out. For this purpose binary Al-Mg alloys containing 6.7 and 10.2 wt-% Mg were melted and solidified in a DTA furnace capable of quenching samples during solidification. Cooling rates of 0.5 and 5 K/min were used and samples were quenched from predetermined temperatures during solidification. The fractions and compositions of the phases were measured by quantitative metallography and SEM/EDX analyses, respectively. These results were used to measure the experimental partition coefficients. The resultant partition coefficients were used to model the concentration profile in the primary phase and the results were compared with equilibrium calculations and experimental profiles. The results of calculations based on the experimental partition coefficients show better consistency with experimental concentration profiles than the equilibrium calculations.
