Microstructure And Mechanical Properties Of Low Activation Alloys With Multi Principal Elements

High entropy alloys break the design concept of the traditional alloys that are based on one or two principle elements and contain at least five principal.High entropy alloys form simple phase constitutes and possess excellent comprehessive properties.To explore advanced low activation structural materials,the alloy system Fe-Cr-V,Ti-Cr-V,Fe-Ti-Cr-V and Fe-Ti-Cr-V-W high entropy alloys based on low activation elements Fe,Ti,Cr,V and W were prepared by arc melting in this paper based on the concept of high entropy alloys.And the microstructure and mechanical properties are investigated.First,the Gibbs free energy of equiatomic alloys could be obtained based on formation criteria of solid solution.Then,optimal composition for multicomponent alloys was obtained by calculating Gibbs free energy in MATLAB software.The variation law of phase constitutes and comprehessive properties were predicting by comparing the?G,?H_mix,?S_mix,?H_el and?of equiatomic and optimized alloys.The study shows that the experimental result is consistent with prediction.The optimized alloys are composed of single body-centered cubic?BCC?solid solution phase.The DSC and homogenized results verify that this solid solution phase has high structural stability and there is on phase transformation below 1000°C.And the mechanical properties also has increased significantly.The equiatomic FeCrV alloy consists of BCC and FCC solid solution phase.After homogenization the FCC solid solution phase transformed into BCC solid solution phase.Compare to equiatomic alloy,the optimized alloy,Fe_34.9Cr_29.6V_35.5,is composed of a single disordered BCC solid solution phase in as-cast and as-homogenized states;there is no any phase transition during the process of homogenization from 296K to 1273K,which can be confirmed by DSC analysis.At room temperature,the mechanical properties of equiatomic alloy,FeCrV,are excellen.The Vickers-hardness and compressive yield strength increased because of the higher degree of solid solution after optimizing the elemental compositions.After homogenization,the Vickers-hardness and compressive yield strength have increased because of fine grain strengthening.The crystal grain of cast Ti-Cr-V alloys is typical dendrite crystals.After homogenization,part of crystals decomposed.The Vickers-hardness,yield strength,fracture strength and fracture strain increased because of solution strengthening.The Vickers-hardness of alloys after optimization calculation decreased somewhat as compared with cast Ti-Cr-V alloys.However,the fracture strength and fracture strain increased obviously.After homogenization,the mechanical properties of Ti-Cr-V alloys increased greatly because of the fine grain strengthening.The equiatomic alloys mainly consist of FeTi phase.However,the alloys after optimization calculation mainly consist of solid solution phase with BCC structure.After homogenizing,the phase composition,Vickers micro hardness(HV_0.2)and yield strength(?_0.2)of Fe-Ti-Cr-V alloys have changed compared to as-cast alloys.The equiatomic FeTiCrVW alloy mainly consists of FeTi phase and solid solution phase with BCC structure.The equiatomic alloy has poor performance such as low strength and low stability.However,the alloy after optimize,Fe_10.78Ti_9.93Cr_8.10V_28.42W_42.77,consists of a single BCC phase with a better stability.The yield strength and fracture strain increase,but the hardness decreases.