摘要
本论文主要研究了Zr-Cu-Al-Hf(Ag)块体非晶复合材料的形成机制,以及室温条件下的压缩力学行为。
利用铜模吸铸法制备了(Zr_(50)Cu_(40)Al_(10))_(98)Hf_2合金及(Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3合金楔形试样,显微组织分析、SEM背散射电子分析、能谱分析及XRD分析表明,两种合金都是在相分离机制下析出晶化相形成块体非晶复合材料的。前者在于高熔点元素Hf较强的析出倾向性;后者由于Ag具有与其他组元较小负的混合焓,进一步促进了相分离的倾向。
(Zr_(50)Cu_(40)Al_(10))_(98)Hf_2合金楔形试样过渡区中领先析出相为单质Hf和Al_3Zr相,晶化区由Hf、Al_3Zr、Cu_(10)Zr_7和CuZr_2四种晶化相组成;由于Ag组元的加入,对合金的相析出产生了影响,(Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3合金过渡区中领先析出相除单质Hf和Al_3Zr外,还有少量的AgZr相,结晶区则是由单质Hf、AgZr、Al_3Zr和CuZr_2四种析出相组成。并通过估算得到了(Zr_(50)Cu_(40)Al_(10))_(98)Hf_2及(Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3块体非晶合金原位自生复合材料形成的临界冷却速率分别为2170K/s和1799K/s,后者的非晶形成能力大于前者。
以铜模吸铸法制备了直径为Φ3mm的Zr50Cu40Al10合金、(Zr_(50)Cu_(40)Al_(10))_(98)Hf_2合金和(Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3合金圆柱形试样,显微组织及XRD分析表明,Zr50Cu40Al10合金试样为非晶材料,(Zr_(50)Cu_(40)Al_(10))_(98)Hf_2和(Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3合金试样都是块体非晶复合材料。
室温压缩实验表明,(Zr_(50)Cu_(40)Al_(10))_(98)Hf_2块体非晶合金复合材料的强度和塑性较Zr50Cu40Al10非晶合金及(Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3块体非晶复合材料都有所提高。其最大应力σmax为2002MPa,最大塑性应变量εp达到8%。通过对三种合金压缩变形行为的研究,确定表征合金塑性变形量大小的最好参数应该是主剪切带与主应力夹角的最大值θ_C~(max)。θ_C~(max)值越大,合金的塑性越好。并建立了剪切角和塑性应变之间的关系式。
通过(Zr50Cu40Al10)Hf2合金和(Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3合金塑性变形区的锯齿流变现象,结合该关系式,验证了试样压缩过程中主剪切带的形成有一定的先后次序,并且在变形过程中,主剪切带会发生一定的偏转,最后试样沿后形成的主剪切带断裂。
The forming mechanism and the compressive behavior under room temperature of a bulk amorphous Zr-Cu-Al-Hf(Ag) alloy have been studied in this paper.
Wedge-shaped samples of (Zr_(50)Cu_(40)Al_(10))_(98)Hf_2 and (Zr_(50)Cu_(40)Al_(10))_(98)Hf_2Ag3 amorphous alloy have been fabricated by copper-mould casting method. The optical microscopy, SEM backscattering, SEM energy spectrum analysis, electron back scattering diffraction (EBSD) technique and X-ray diffraction were used for determining the microstructure, the precipitation phases in different regions of the wedge-shaped samples. The results indicate that the formation of these two bulk amorphous composites were due to the phase segregation before precipitation. The reason lies in the higher melting point for Hf, and the positive mixing enthalpy for Ag with other elements.
The precipitation phases in the transition zone for the (Zr_(50)Cu_(40)Al_(10))_(98)Hf_2 amorphous alloy wedge ingot are Hf and Al_3Zr, and the crystallization zone is composed of Hf、Al_3Zr、Cu_(10)Zr_7 and CuZr_2; while the precipitation phases are Hf, Al_3Zr, and AgZr in the transition zone for the (Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3 amorphous alloy wedge ingot, and the crystallization zone is composed of Hf、AgZr、Al_3Zr and CuZr_2. The critical cooling rates for the above two alloys were estimated as 2170 K/s and 1799 K/s, respectively. Obviously the later has better glass forming ability than the first one, owing to the addition of Ag element.
Rods of 3mm in diameter for the Zr50Cu40Al10, (Zr_(50)Cu_(40)Al_(10))_(98)Hf_2 and (Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3 alloys have been made by copper mould casting. Microscopy and XRD analyse indicate that the rod for Zr50Cu40Al10 alloy is fully amorphous, and the rods for (Zr_(50)Cu_(40)Al_(10))_(98)Hf_2 and (Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3 alloy are bulk amorphous alloy composites.
Compressive test indicates that the (Zr_(50)Cu_(40)Al_(10))_(98)Hf_2 alloy has both the best compressive strength and ductility among the three alloys, and the maximum stressσmax is as high as 2002Mpa, and the maximum strainε_p is as large as 8%. Based on the compression behavior and the theoretical analysis of the three alloys, the best parameter for describing the ductility strain of the amorphous alloy is the maximum of the angleθ_C~(max) between the main sheer band and the main stress. Largerθ_C~(max) means better ductility for an amorphous alloy. And a relation between the shear band angles and the ductility strain has been established.
Based on this relation and the serrated flow in the ductile deformation region for (Zr_(50)Cu_(40)Al_(10))_(98)Hf_2 and (Zr_(50)Cu_(40)Al_(10))_(95)Hf_2Ag_3 alloys, it is verified that the main sheer bands were formed in sequence, and would deflect during the process of deformation, and the whole sample would break along the last main sheer band.
引文
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