| The characteristics of strain fatigue and wear resistance in Fe-17Mn-5Si-10Cr-5Ni, Fe-18Mn-5Si-3Cr-3Ni-1V,Fe-14Mn-4Si-10Cr-5Ni-1Nb shape memory alloys are measured by cyclic bending fatigue test and wear resistance test.Then mechanics behavior,stress-induced martensitic transformation and their relation of these alloys during the processes of cyclic bending and wear abrasion are respectively studied by X-ray diffraction(XRD) analysis,Optical Mircoscope and electron scanning microscope(SEM) observations,etc,in order to develope the useful characteristics of the cheaply functional material besides shape memory effect,enlarge the application of engineering.It is found by the analysis of XRD that theγ→εmartensitic transformation and its reverse transformation occur under the cyclic bending,which proves the reversibility of the movement from FCC to HCP under mechanical force.From cyclic bending fatigue test,Fe-Mn-Si alloy shows good strain fatigue resistance,such as under the strain of 1% cyclic bending fatigue life of Fe-17Mn-5Si-10Cr-5Ni is 19223 times,that of Fe-18Mn-5Si-3Cr-3Ni-1V is 2237 times,that of Fe-14Mn-4Si-10Cr-5Ni-1Nb is 5127 times which is much better than stainless steel with 985 times in the same test conditions.The repetitive stress induceγ→εmartensitic transformation and its reverse transformation with the move of Shockley part dislocations cause the deformation in the bent cyclic course,unlike the plastic sliding deformation in usual materials by whole dislocations destroy the crystal structure.Simultaneously,the repetitive stress induceγ→εmartensitic transformation and its reverse transformation in the cyclic course can enhance the fatigue life of Fe-Mn-Si alloy by reducing crack-tip stress,restraining plastic sliding deformation and delaying the formation and extension of microcracks. Consequently,Fe-Mn-Si alloy shows good strain fatigue resistance.By SEM analysis and XRD analysis,it is found that the bending-fatigue fractured section of Fe-Mn-Si alloy shows quasi-cleavage brittle rupture type and possesses nearly 100%εmartensite.It's found that the wear resistance of Fe-Mn-Si alloy takes on excellent friction wear resistance in oily lubrication with abrasive wear mechanism,and its mass loss is changed with load,anneal temperature and anneal time.It is known from XRD analysis and SEM observation,that stress induceγ→εmartensitic phase transformation and its phase transformation pseudoelasticity in Fe-Mn-Si alloy can improve its wear resistance in oily lubrication by reducing crack-tip stress,restraining plastic sliding deformation and delaying the formation and extension of microcracks. |
PDF Full Text Request