Organizations And Properties Of Fe-Ni Based Magnetic Alloys Fabricated By Laser Additive Manufacturing(LMDF)

Fe-Ni-based magnetic materials have good mechanical properties and magnetic properties,which have been widely used in advanced civil and military technology fields.With the advent of the intelligent era,higher requirements have been put forward for the properties and preparation methods of sensor materials.The acquisition of functional-structure-efficient materials in the same production chain has become a new scientific challenge.Laser additive manufacturing(LMDF)has many advantages,such as high degree of freedom,low thermal input,accurate processing,easy to realize intelligent and automatic production,etc.,which is an ideal solution to solve this scientific challenge.Two alloys,Fe-Ni-Sm-Al-Ti and Fe-Ni-Co-Sm-Al-Ti,were fabricated by laser additive manufacturing(LMDF).The microstructure and properties of the alloy were characterized by scanning electron microscopy(SEM),X-ray diffraction analysis(XRD),vibration sample magnetometer(VSM)and friction and wear tests.The effects of alloy composition,heat treatment process and mechanical vibration assistance on the microstructure,magnetic and mechanical properties of the two alloys were investigated.The results show that:In the original state of laser additive manufacturing,with the increase of Sm content,the adverse effect of laser additive manufacturing on alloy materials is suppressed to a certain extent.The mechanical properties of the alloy are obviously improved.When the Sm content is 1wt.%,the alloy has the best soft magnetic properties,the saturation magnetic induction strength and coercivity are 144.74emu/g and 21.16Oe,respectively.After annealing treatment,the microstructure of Fe-Ni-Sm alloy is improved obviously.The maximum magnetostrictive strain?s of the alloy is greatly increased,and the magnetic field response velocity(d?/d H)of the alloy is effectively increased.When the Sm content is4wt.%,the maximum?_s reaches 32.80ppm.Compared with without Sm,it increased by35.93%.The d?/d H of the alloy reaches the maximum value(0.070),which is 70.00%higher than that of the alloy without Sm.The microhardness,wear resistance,strength and toughness of the alloy are improved obviously by annealing treatment.When the ratio of Ni-Co is different,the saturation magnetic induction intensity of Fe-Ni-Co-Sm-Al-Ti alloy is greatly increased with the increase of the proportion of Co.When the Co content is 30wt.%,the saturation magnetic induction intensity reaches the maximum,which is about 183.33emu/g.Compared with the Fe-Ni alloy without composition optimization,the saturation magnetic induction intensity increased by about 26.43%.With the increase of Co content,the microhardness,tensile strength and wear resistance of the alloy are greatly improved.The maximum hardness is 538.26HV_0.3 when the Co content is 30wt.%,and the hardness is increased by about 118.36%compared with that when the Co content is10wt.%,and the wear weight loss is decreased by about 70.83%.The microstructure of Fe-Ni-Co-Sm-Al-Ti alloy is refined and the microstructure uniformity is improved by the addition of mechanical vibration.At low and medium frequencies(?600Hz),the soft magnetic properties of the alloy are better improved.Compared with the condition without mechanical vibration,the saturated magnetic induction intensity is increased by 6.85%?9.71%,while the coercivity(H_c)of the alloy is decreased by34.78%?48.73%.When the vibration frequency is 600Hz,the Fe-Ni-Co-Sm-Al-Ti alloy has better comprehensive properties,and its saturation magnetic induction intensity is200.77emu/g,and its coercivity is 47.79Oe.The wear weight loss of the alloy is about33%?45%of that of the alloy prepared at other vibration frequencies.