Effect of Equal Channel Angular Pressing on Mechanical and In-Service Properties of Mg-1%Zn-0.3%Ca AlloyWednesday (26.09.2018) 11:30 - 11:45 S1/01 - A3 Part of:
In this work, the effect of equal channel angular pressing (ECAP) on microstructure, texture, mechanical properties, corrosion resistance and fatigue behaviour of Mg-1%Zn-0.3%Ca alloy was studied. Route Bc ECAP was conducted using a die with an angle of 120° between the entry and exit channels. The deformation temperature was decreased in 25 °C steps from the initial 400 °C to 300 °C at the final, 10th pass (with two passes conducted at each temperature). In a homogenized state the alloy had a microstructure with an average grain size of 104 µm. ECAP led to a significant grain refinement with the formation of the grain structure with the average grain size of 3.8 µm. The grain refinement did not lead to an expected strengthening of the alloy. The values of the yield strength and the ultimate tensile strength in the initial state were 92 MPa and 194 MPa, respectively, while after ECAP they rose to mere 106 MPa and 215 MPa. However, the tensile elongation increased from 12.8% in the initial state to 23.9% after deformation. It is believed that such behaviour (slight strengthening with a significant increase in ductility) is typical for magnesium alloys processed by ECAP due to the formation of an inclined basal texture . The comparison of values of corrosion rate determined by measurements of weight loss and hydrogen evolution showed that the grain refinement caused by ECAP does not reduce the corrosion resistance in 0.9% NaCl solution. The mass loss was 1.72 ± 0.86 mg/cm2*day in the initial state of the alloy and 2.96 ± 1.18 mg/cm2*day after ECAP. The corrosion rate measured by hydrogen evolution tests was 1.51 ± 0.21 ml/cm2*day and 2.67 ± 1.18 ml/cm2*day for the initial and ECAP-treated states, respectively. The investigation of fatigue behaviour of the alloy in the initial state and after ECAP showed that the grain refinement has a positive effect on the fatigue limit. The value of the fatigue limit measured by high-cycle fatigue tests increased from 90 MPa in the initial state to about 100 MPa after ECAP.
Funding for this research provided by the Russian Science Foundation (grant #17-13-01488) is gratefully acknowledged.
 S.R. Agnew, J.A. Horton, T.M. Lillo, D.W. Brown. Enhanced ductility in strongly textured magnesium produced by equal channel angular processing // Scripta Materialia, 2004, 50, pp.377–381.
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