Effect of secondary heat treatment on the magnetic properties and thermal expansion coefficient of Super-Invar alloy
Influence of secondary heat treatment on the magnetic properties and thermal expansion characteristics of finished Super-Invar alloy were investigated.By conducting the secondary heat treatment within the temperature range of 900-1 100 ℃,the microstructure of the alloy was optimized.XRD characterization results indicated that the alloy maintained the fcc phase structure before and after heat treatment,with no new phase generated,but more dis-tinct crystal orientation.EBSD characterization results revealed significant grain growth,reduced twinning density,and improved grain uniformity after the secondary heat treatment.MFM characterization results showed that the magnetic domain size increased,while the intensity decreased.Fine domains underwent broadening and merging,and the number of domain walls decreased after the secondary heat treatment.The testing results of magnetic prop-erties and coefficient of thermal expansion demonstrated that,as the temperature of the secondary heat treatment in-creased,the magnetic properties of the alloy improved significantly,accompanied by a noticeable increase in the co-efficient of thermal expansion(CTE).However,it was observed that the T1050 sample exhibited high magnetic performance but low CTE.By measuring and analyzing the B2,500-T curve of the sample at-20 to 120 ℃,it was found that the decay of B2,500 with increasing temperature of the T1050 sample was greater than other samples,which might be a reason for its high magnetic properties and low CTE characteristics.
super-invar alloymagnetic propertiescoefficient of thermal expansionsecondary heat treatment
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