| Magnesium is one of the commonly used non-ferrous metals because its advantages,such as light weight and good ductility.However,its poor corrosion resistance restricts wide application in engineering.In order to achieve the requirements of engineering structure materials and environmental protection,Mg/Al laminates with both advantages by coating 5052 aluminum alloy on the surface of AZ31 magnesium alloy were fabricated by hot rolling.Stamping forming is necessary process for the practical application of Mg/Al laminates,and stress relaxation has great impact on product quality.Therefore,the research on microstructure,mechanical properties and stress relaxation behavior of Mg/Al laminates has certain theoretical and practical value.In this paper,Mg/Al laminates was fabricated by one pass hot rolling at380℃.The rolling rate was 4.08 m/min,6.12 m/min and 8.13 m/min,respectively and reduction was 33%,40%and 47%,respectively.The thermal tensile and stress relaxation tests were performed at different temperature（100℃,150℃,200℃and 250℃）.The microstructure of Mg/Al laminates was observed by optical microscope and scanning electron microscope,and the mechanical properties of high temperature were tested by universal tensile test machine.The influence of deformation temperature and rolling process on microstructure and high-temperature mechanical properties of Mg/Al laminates was studied.A theoretical model for stress relaxation of Mg/Al laminates has been established in a certain temperature range.Reduction ratio and rolling rate significantly improved the microstructure and the ability of compatible deformation in Mg/Al laminates.With the increase of the rolling speed and reduction,the shear zone became wider,the number of fine grains increased in the interface area in the Mg/Al laminates.The banded large grains disappeared and equiaxed grains appeared in the magnesium matrix of the annealed Mg/Al laminates,which is due to the large distortion and the more internal deformation energy at the interface of Mg/Al.The variation trend of stress-strain curves of Mg/Al laminates was similar at 100℃,150℃,200℃and 250℃.In the early stage of deformation,the stress increased continuously with the increase of deformation,reached a peak value and then gradually decreased until fracture.Temperature is a crucial factor for the mechanical properties of Mg/Al laminates.With the increase of temperature,the yield strength and tensile strength of the Mg/Al laminates were reduced,and the elongation had keep pace with the change of temperature,because the non-basal slip of magnesium was initiated at high temperature and thus enhanced the plasticity of the laminates.As rolling rate is 8.13 m/min and deformation temperature is 200℃,the yield strength and tensile strength increased firstly and then decreased with the increase of the reduction,and there are the negative correlation between the elongation and the reduction,due primarily to work hardening in Mg/Al laminates.The yield strength reached a maximum of 93 MPa at the reduction of 40%,the elongation（δ）reached a maximum value of 47.8%at the reduction of 33%.Rolling process had an effective effect on grain size of the Mg/Al laminates during the stress relaxation.With the increase of reduction and rolling rate,the grain size of magnesium decreased,thus render accelerating the strain relaxation rate.However,the size of the magnesium particles has little effect on the limits of stress relaxation.The relaxation stress had kept pace with increasing the reduction.With the rolling rate increased,the stress relaxation resistance becomes better.The stress relaxation curve of Mg/Al laminates can be divided into two stages:in the first stage,the stress drops sharply with the increase of time,the second stage,the stress drops slowly,and gradually approaches to a constant value,that is the stress relaxation limit.Temperature has more obvious influence on stress relaxation.With the temperature increased,stress relaxation became faster.The stress relaxation behavior of the Mg/Al laminates in the temperature range of 100°C to 250°C conformed to the equation:σ=σ（∞）+A1*exp（-（t-x0）?a）+A2*exp（-（t-x0）?b）+A3*exp（-（t-x0）?c）... |
