Effect of hot rolling on microstructure and damping capacity of Twin Roll Cast ZK60 alloy

Abstract

ZK60 alloy strip with 3·5 mm thickness which produced by Twin Roll Casting (TRC) was used in this paper. The effect of hot rolling and sequential annealing on microstructure and damping capacity of the ZK60 alloy was studied by using optical microscope (OM) and dynamic mechanical analyzer (DMA). The dendrite structure was present in TRC ZK60 alloy strip before and after annealing heat treatment. The small and equiaxed recrystallised grains were obtained after annealing at 350°C for 103 s in hot rolled ZK60 alloy sheet. The hot rolling and the sequential annealing improved the room temperature mechanical properties and damping capacity of TRC ZK60 alloy. The tensile strength, yield strength and elongation of as-annealed TRC ZK60 alloy strip and hot rolled ZK60 alloy sheet were 207, 184 MPa, 2·6% and 418, 349 MPa, 18·6%, respectively. The room temperature damping value (Q− 1) of ZK60 strip and ZK60 alloy sheet after annealing heat treatment was 0·0085 and 0·0119, respectively. The damping peaks were present in ZK60 strip and ZK60 alloy sheet after annealing heat treatment. The activation energy of the ZK60 strip and ZK60 alloy sheet were 110·63 and 90·18 KJ mol− 1. The value of activation energy of ZK60 alloy sheet was very close to the boundary activation energy of pure magnesium (92 KJ mol− 1). The damping peak of ZK60 alloy sheet after annealing treatment was the grain boundary peak.