The Influence Of Composition To Structure And Performance In Fe-Mn-Si Based Alloys

In this paper, nine kinds of Fe-based Shape Memory Alloys (SMA) were designed by accommodating different content of three elements Mn, Cr, Ni to compare with their Shape Memory Effects (SME). Combing with the mechanics performance and X-ray diffractometry, the authour has studied on the influences of different quench temperature and different composition of SMA on the SME by means of bending deformation method. Microstructures of 5#, 6# SMA with tensile deformation were investingated by optical microscope, SEM, TEM.Results show that, accommodating different composition of SMA, the difference Δσ is increased and the SME of SMA is improved. The SME of 5# SMA is the best one among nine kinds of SMA.The quench temperature before bending and the anneal temperature of reversion after bending have great effect on the SME of the experiment alloys after machining, the best SME can be obtained when the quench temperature is 650℃ and the anneal temperature of reversion is 600°C. When the temperature is 475~1000℃, the shape recovery ratio of SMA increases first and then decreases with the rising of quench temperature.The highest shape recovery ratio of 5# SMA can reach 95.19% when the pre-strain is 2%, and the highest shape recovery stain ε_r can reach 5.771% when the pre-stain is 8%. Between 2%~10% pre-strain, the shape recovery ratio of SMA decreases continuously, and the shape recovery stain ε_r increases first and then decreases with the rising of pre-strain.The microstructure of 5# SMA is more uniform and finer than that of 6# SMA after 650℃×30min quench. After tensile deformation of 8% pre-strain, the density of stress-induced e matensite which forms the paralle distribution of stacking fault bands is higher, and the cross is subtile in 5# SMA. However, a mass of dislocations is obtained and stress-induced e matensite crosses badly in 6# SMA. After 600℃×30min anneal of reversion, a spot of ε matensite without reversion, α' matensite anddislocations can be obtained in the y autensite matrix in 5# SMA. Whereas a great deal of thick stress-induced e matensite without reversion and crossing badly, a' matensite and tangled cystiform dislocations can be obtained in the autensite matrix in 6# SMA.The experiment in this paper had paid more attention to practical engineering applications on the coupler of petroleum tubes. By means of optimizing the alloy's composition by accommodating different content of elements, medium-sized pre-deformation and heat-treatment can improve SME remarkably. The result can be used as the reference for further development of this alloy.