Development Of New Process For Preparation Of High-Entropy Alloy(FeCoCrNiMn) And Research On Product Application

The FeCoCrNiMn high-entropy alloy,characterized by its unique face-centered cubic（FCC）structure and outstanding plasticity,is the focus of this study.However,it is known that the FeCoCrNiMn high-entropy alloy obtained through melting may have certain defects.As a result,this paper aims to prepare FeCoCrNiMn high-entropy alloy using the mechanical alloying（MA）and spark plasma sintering（SPS）method.To investigate the impact of introducing other elements on the microstructure and mechanical properties of FeCoCrNiMn high-entropy alloy,this study selects Mo element as the additive and explores its influence.Analysis will be performed using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,optical microscopy,Vickers hardness tester,and universal testing machine.The main research work and conclusions are summarized as follows:1)This passage describes the preparation of FeCoCrNiMn high-entropy alloy powder using mechanical alloying,where the alloying process gradually completes with increasing ball milling time.Ultimately,after 40 hours of ball milling,the most homogeneous composition and optimal state of FeCoCrNiMn high-entropy alloy powder are obtained.At this stage,the grain size of FeCoCrNiMn Mo high-entropy alloy powder is 7.8 nm,and the lattice constant is 2.868?.In addition,the solid solution sequence of FeCoCrNiMn high-entropy alloy during mechanical alloying is found to be Mn→Ni→Co→Fe→Cr.2)This passage describes the preparation of FeCoCrNiMn high-entropy alloy bulk using spark plasma sintering.As the sintering temperature increases,the phase composition of the alloy is mainly composed of FCC phase,σphase,and a small amount of M₂₃C₆（Cr,Fe,Co）carbides,showing a consistent trend.The alloy completes the sintering process at 1100°C.As the temperature increases,the hardness of the alloy first increases,then decreases,and then increases again.The density of the alloy increases and ultimately reaches 7.070 g·cm^-3.At this point,the strength-ductility ratio also reaches its optimal value.Taking all factors into consideration,the optimal sintering temperature for this high-entropy alloy is found to be 1100°C.3)The optimal process for preparing FeCoCrNiMn high-entropy alloy is as follows:In the first step,FeCoCrNiMn high-entropy alloy powder is obtained by mechanical alloying for 40 hours using high-energy ball milling.In the second step,the FeCoCrNiMn high-entropy alloy powder obtained in the first step is used to prepare FeCoCrNiMn high-entropy alloy bulk using spark plasma sintering.The specific sintering process is as follows:the material is pre-pressed by applying pressure of 12.5MPa within 5 minutes after heating to 600℃.Then,the heating rate is set to100℃·min^-1,and the sintering is carried out at 1100℃for a period of 30 minutes,while maintaining a constant pressure of 30 MPa during the process.Finally,the material is cooled down together with the furnace,and FeCoCrNiMn high-entropy alloy bulk is obtained.4)FeCoCrNiMn Mo high-entropy alloy powder was prepared using mechanical alloying,and the alloying process gradually completed with increasing ball milling time.Eventually,after 40 hours of ball milling,the most homogeneous composition and optimal state of FeCoCrNiMn Mo high-entropy alloy powder were obtained.At the40-hour mark,the grain size of FeCoCrNiMn Mo high-entropy alloy powder was 7.7nm,and the lattice constant was 3.617?.Using the optimal sintering temperature of1100°C,FeCoCrNiMn Mo high-entropy alloy bulk was prepared by spark plasma sintering,with a phase composition consisting of the FCC primary phase,σphase,and a small amount of M₂₃C₆ carbides（M=Fe,Co,Cr,Mo）.The microstructure morphology showed large gray low-Mo FCC matrix phase and irregular white Mo-rich precipitates（σphase）.5)Through a series of comparisons of the mechanical properties of FeCoCrNiMn Mo and FeCoCrNiMn high-entropy alloys,it was found that Mo element has a significant strengthening effect on FeCoCrNiMn high-entropy alloy.The compressive strength and hardness of the alloy are significantly improved,but the plasticity shows a certain decrease.Moreover,the wear resistance of the high-entropy alloy is significantly increased,and the wear mechanism is mainly abrasive wear and slightly adhesive wear.From the fracture morphology,it is concluded that the fracture mechanism of FeCoCrNiMn Mo high-entropy alloy is a combination of plastic fracture and transgranular fracture,while FeCoCrNiMn high-entropy alloy exhibits single plastic fracture.