一种兼具优异软磁性能和耐腐蚀性能的高熵合金

耐腐蚀性能差限制了大多数软磁材料在腐蚀环境中的应用,尤其是海洋环境.因此,提高软磁材料的耐腐蚀性能是其在海洋环境工业应用的关键.然而,磁性能和耐腐蚀性能之间存在矛盾关系,耐腐蚀性能的主要贡献元素Cr的反铁磁性会严重损害合金的磁性能.本研究开发了一种兼具优异力学性能和耐腐蚀性能的软磁高熵合金(Fe_(2.25)Co_(1.25)Cr)_(94)Al_(6),其综合性能优于绝大多数已报道的传统和高熵合金软磁材料.该合金的饱和磁化强度高达141.88 emu g^(-1),矫顽力仅有2.9 Oe;其在模拟海水中的耐腐蚀性能优于大多数已报道的软磁高熵合金和传统304不锈钢;同时,该合金还具有优异的力学性能,屈服强度高达1.1 Gpa,压缩断裂延伸率超过33%,硬度高于469 HV.这种新型的耐蚀软磁高熵合金有望满足海洋环境中的使役要求,解决软磁材料在海洋腐蚀环境下的使役难题.

Anomalous microstructure and tribological evaluation of AlCrFeNiW_(0.2)Ti_(0.5)high-entropy alloy coating manufactured by laser cladding in seawater

To evaluate the potential of high entropy alloys for marine applications,a new high entropy alloy coating of AlCrFeNiW_(0.2)Ti_(0.5)was designed and produced on Q235 steel via laser cladding.The microstructure,microhardness and tribological performances sliding against YG6 cemented carbide,GCr15 steel and Si_(3)N_(4)ceramic in seawater were studied in detail.The AlCrFeNiW_(0.2)Ti_(0.5)coating showed an anomalous’sunflower-like’morphology and consisted of BCC and ordered B2 phases.The microhardness was approximately 692.5 HV,which was 5 times higher than substrate.The coating showed more excellent tribological performances than Q235 steel and SUS304,a typical material used in seawater environment,sliding against all three coupled balls in seawater.Besides,the wear and friction of AlCrFeNiW_(0.2)Ti_(0.5)coating sliding against YG6 in seawater were most mild.The main reason was the generation of Mg(OH)_(2),CaCO_(3),metal oxides and hydroxides and the formation of protective tribo-film on the worn surface of AlCrFeNiW_(0.2)Ti_(0.5)coating in the process of reciprocated sliding.This would effectively hinder the direct contact between the worn surfaces of AlCrFeNiW_(0.2)Ti_(0.5)coating and YG6 ball,resulting in a decrease of friction coefficient and wear rate.Thus the YG6 was an ideal coupled material for AlCrFeNiW_(0.2)Ti_(0.5)coating in seawater,and the coating would become a promising wear-resisting material in ocean environment.

Microstructure and mechanical properties of C_(x)Hf_(0.25)NbTaW_(0.5) refractory high-entropy alloys at room and high temperatures

The microstructure and mechanical properties of as-cast and isothermally annealed C_(x)Hf_(0.25)NbTaW_(0.5)(x=0,0.05,0.15,0.25)refractory high-entropy alloys(RHEAs)were studied.Both the as-cast and annealed RHEAs consisted of disordered body-centered cubic solid solution phase and metal carbide(MC)phase with a face-centered cubic crystal structure(Fm-3 m space group).The primary carbides were enriched with Hf and C elements and tended to form lamellar eutectic-like microstructure in the interdendrites.The lamellar eutectic-like structure in the interdendrites would be formed from the decomposition of sub-carbide M_(2)C under the influence of Hf element.After isothermal annealing,slatted carbides were precipitated on the matrix,and the distribution became more uniform with high C content.The formation of carbides strongly influenced the mechanical properties both at room and high temperatures.The yield strength values of C_(x)Hf_(0.25)NbTaW_(0.5) RHEA at 1473 and 1673 K were 792 and 749 MPa,respectively.The result had exceeded the high temperature mechanical properties of currently known RHEAs.Moreover,this RHEA exhibited high-temperature performance stability and excellent plasticity,exceeding 30 and 50%at room and elevated temperatures(above 1273 K),respectively.During thermal deformation,carbon-containing RHEAs obtained more severe work hardening than that of ACHO RHEAs,and required greater dynamic recrystallization to achieve the dynamic equilibrium.