CrFeNi_(2)B_(x)高熵合金的微观组织及力学性能

Microstructure and mechanical properties of CrFeNi_(2)B_(x)high-entropy alloys

采用非自耗真空熔炼法制备了CrFeNi_(2)B_(x)(x=0、0.2、0.4、0.6、0.8和1.0)高熵合金,并研究了B元素对CrFeNi_(2)合金的晶体结构、显微组织和室温力学性能的影响。结果表明:CrFeNi_(2)合金为单相FCC结构,随着B元素的加入,CrFeNi_(2)B_(0.2)合金中的FCC相产生了晶格畸变并有较硬的第二相硼化物生成,形成了FCC相和FCC相+不规则片状硼化物相的亚共晶组织;当x=0.4时,形成了FCC相+不规则片状硼化物相的共晶组织;当x>0.4时,形成了条状或者块状硼化物相和FCC相+不规则片状硼化物相的过共晶组织。随着硼化物含量的增加,合金的硬度和屈服强度增加,塑韧性下降。CrFeNi_(2)B_(0.4)合金具有最好的综合力学性能,其硬度为248.4 HV30,屈服强度、断裂强度和压缩率分别为803.8 MPa、1080.1 MPa和32.2%。当δ≥3.25%,-27.04 kJ/mol≤ΔH_(mix)≤-5.15 kJ/mol和6.89≤VEC≤8.23时,含硼高熵合金趋向于形成金属化合物。

CrFeNi_(2)B_(x)(x=0,0.2,0.4,0.6,0.8 and 1.0)high-entropy alloys were fabricated by non-self-consumable vacuum melting method,and the effect of element B on crystal structure,microstructure and room temperature mechanical properties of the CrFeNi_(2) alloy was studied.The results show the CrFeNi_(2)alloy is single-phase FCC structure.With the addition of B element,the FCC phase in the CrFeNi_(2)B_(0.2) alloy has lattice distortion and a hard second phase boride is formed,forming the hypoeutectic structure of FCC phase and FCC phase+irregular lamellar boride phase.When x=0.4,the eutectic structure of FCC phase+irregular lamellar boride phase is formed.When x>0.4,the hypereutectic structure of strip or block boride phase and FCC phase+irregular lamellar boride phase is formed.With the increase of boride content,the hardness and yield strength of the alloy increase,and the plastic toughness decreases.The CrFeNi_(2)B_(0.4) alloy has the best comprehensive mechanical properties,its hardness is 248.4 HV30,and the yield strength,fracture strength and fracture strain are 803.8 MPa,1080.1 MPa and 32.2%,respectively.Whenδ≥3.25%,-27.04 kJ/mol≤ΔH_(mix)≤-5.15 kJ/mol and 6.89≤VEC≤8.23,the high entropy alloys containing boron tend to form metallic compounds.