Study On Microstructure,phase Transformation And Magnetic Properties Of CuAlMn Shape Memory Alloy

Heusler-type CuAlMn magnetic shape memory alloy has been widely studied due to its magnetic,electrical,stress,damping and other coupling characteristics.Combining magnetic field regulation with its damping characteristics may expand its application prospect,how to improve the magnetic properties of CuAlMn alloy is the key to its application in magnetic field.Based on the previous research results on the magnetic properties of CuAlMn alloy,the relationship between heat treatment and microstructure,martensitic transition and magnetic properties of CuAlMn alloy was studied in detail in this paper.The specific research programmes and results are as follows:（1）The Cu₇₁Al_16+xMn_13-x（x=0,1,2,3）ingot alloy was prepared by arc melting method,and the effect of quenching process on the microstructure and magnetic properties of the alloy was studied.The as-cast alloy is irregular large grains at room temperature,and the grains grow slightly after heat treatment.The phase transition temperature of the alloy moves to the high temperature region with the decrease of Mn content（the increase of Al content）,and the phase transition temperature of the alloy after heat treatment increases.The phase transition temperature of Cu₇₁Al₁₉Mn₁₀alloy is close to room temperature.The direction of external magnetic field has no obvious effect on the phase transition temperature in resistance-temperature.The magnetization of Cu₇₁Al₁₉Mn₁₀alloy after heat treatment has a sharp upward trend in the process of high temperature heating magnetization,and the magnetization increases significantly after cooling.The hardness of the alloy increases slightly after heat treatment,but decreases after Mn content reaches 11（at%）.（2）The Cu₇₁Al₁₉Mn₁₀alloy ribbons were prepared by vacuum melt quenching,and the effects of different annealing temperatures on the microstructure,phase transformation and high-low temperature magnetic properties of the ribbons were studied in detail.The ribbons below 525 K heat treatment temperature are singleβphase,andαandγ₂phases appear in the alloy above 575 K heat treatment temperature.In the process of high temperature heating magnetization,an obvious magnetic peak appears at 575 K.After cooling to room temperature,the magnetization intensity is significantly improved.The transformation temperature of the ribbon below 550 K is significantly higher than that of the original ribbon,while the martensitic transformation in the ribbon after heat treatment reaches 575 K disappears.The fracture mode of ribbons above 575 K heat treatment temperature changes from ductile fracture to brittle fracture.At 575 K,the hysteresis loop of the ribbon changes from paramagnetic state to ferromagnetic state,and the magnetization increases sharply,reaching the maximum at 650 K.The direction of external magnetic field has a certain influence on the magnetization,coercivity and remanence of the ribbon.The ribbon sample has glass state at low temperature,and the spin glass trend becomes more obvious with the increase of heat treatment temperature.