| Fe-Mn-Si shape memory alloy (Fe-Mn-Si SMA) occurs martensitic transformation and transformation distortion in order to adapt change of macroscopical force in the condition of exerting outside mechanical stress. This characteristic is called the stress self-accommodation characteristic.The stress self-accommodation characteristic of Fe-Mn-Si SMA is close relative to mechanics property. It's found that the Fe-Mn-Si SMA possess good wear-resisting performance, anti-strain and anti-stress fatigue characteristic in despite of its lower rigidity in some condition, because of having stress self-accommodation characteristic.The main reason for appearing this characteristic is that it has the partial dislocation reversible movement and transformation pseudoelasticity. The factors effected the stress self-accommodation characteristic are: (1) the value of stress and strain;(2)the surface temperature value ;(3) ingredient content and proportion component of Fe-Mn-Si SMA.The wear-resisting performance and the strain fatigue characteristic in four kinds of Fe-Mn-Si SMA with different components are investigated by sliding friction test and strain fatigue test; Some automobile transmission gearbox idler is made using the alloy and carried on fatigue tests under the complex stress condition; Pressure specimen designed and manufactured is carried on compression test ; The transformation and microcosmic mechanism of the SMA during the processes of wear abrasion and strain fatigue are respectively studied by X-ray diffraction(XRD),scanning electron microscope(SEM) and transmission electron microscopy (TEM) etc.It's found that the Fe-Mn-Si SMA has the friction and wear characteristic of the common austenitic metal material in the dry friction, and the wear mechanism is adhesive wear; but it has good friction and wear characteristic and the wear mechanism is abrasive wear in lubrication. Moreover, Fe-Mn-Si SMA wear mass losses does not increase along with increasing the load ,while there is a better load that in which, the wear mass losses is the least in lubrication.Fe-Mn-Si SMA shows good strain fatigue resistance with cyclic bending fatigue life of 1302 times under the strain amplitude of±3% much better than stainless steel with 80 times in the same test conditions. And its cyclic tension-compression fatigue life is 1300 times under the strain amplitude of±1.5%, also much better than U71Mn heavy rail steel with 120 times. The bending-fatigue fractured section of Fe-Mn-Si SMA specimen possesses nearly 100%εmartensite with quasi-cleavage rupture type.It is indicated that from the analysis of XDR, the observations of SEM and TEM, in the conditions of lubrication, bending and tensile compression cycle, the stress self-accommodation characteristic of the alloy results in the appearance ofγ→εmartensitic positive and reverse transformation, reduces the stress concentration,suppresses the plastic slipping deformation and reduces the rate of microcrack's formation and expansion.Consequently it improves the mechanics property of the wear-resisting performance and fatigue life.The Fe-Mn-Si SMA possess better machining property.According to the fatigue test of some automobile transmission gearbox idler made of this material under the complex stress condition , it is proved that, in the same condition, the fatigue life of this idler is 10 times more than that of 1Cr18Ni9Ti austenitic stainless steel idler; The compression test and calculation to specimen made of the alloy proves that, when the temperature changes between -50℃and +50℃, the temperature stress in rail can be reduced 11% as long as welding Fe-Mn-Si SMA according to 3% proportion in rail, so it is proved again, the stress self-accommodation characteristic of the alloy is the basic reason for its good mechanics property.
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