MA和软第二相对Cr／Cr2Nb复合材料组织与性能的影响

Effect of MA and Soft Second Phase on Microstructures and Properties of Cr/Cr_2Nb Composite Materials

采用机械合金化(MA)+热压工艺来制备以Cr固溶体为软第二相的Cr/Cr2Nb复合材料。研究了不同配比成分的Cr,Nb元素粉经20h球磨后,在1250℃,0.5h热压工艺下所获得的Cr/Cr2Nb复合材料的组织和性能。结果表明,随着偏离Laves相化学配比的Nb含量减小,合金的致密度、强度、塑性应变均增加,而维氏硬度减小,不同配比成分的合金均具有良好的室温断裂韧性。Laves相Cr2Nb含量高达78%的Cr-25Nb合金的组织均匀,Cr固溶体与Laves相间隔分布,晶粒尺寸达到微/纳米级,屈服强度和抗压强度分别高达1949MPa和2044MPa,塑性应变达到了7.26%。与熔铸工艺制备的Cr/Cr2Nb复合材料相比,合金的强度及塑性都有明显提高,充分实现了细晶和软第二相综合增韧的效果。

Cr/Cr2Nb composite materials with soft second phase Cr solid solution were prepared by mechanical alloying and hot pressing. The microstructures and mechanical properties of Cr/Cr2Nb composite with different Nb Content prepared by MA for 20 h and hot pressing at 1250 ℃ for 0.5 h were investigated. The results indicate that with the decrease of Nb content, which is off-stoichiometry Laves phase, the alloys have higher relative density, compress strength and strain, and lower Vickers hardness. All alloys with different composition have good room temperature fracture toughness. Cr-25Nb alloy that the laves phase is up to 78% possesses uniform microstructure with fine or nano-grains, yield strength of 1949 MPa, compress strength of 2044 MPa and strain of 7.26%. Compared with Cr/Cr2Nb composites prepared by arc-melting, the strength and ductility of the alloys increases greatly, which reflects the toughening effect by both fine grain and soft second phase.