EFFECT OF COOLING RATE AND ASPECT RATIO ON MECHANICAL PROPERTIES OF Ti-BASED AMORPHOUS ALLOY COMPOSITES
Juan MU,Dongmei WANG,Yandong WANG()
Key Laboratory for Anisotropy and Texture of Materials (MOE), Northeastern University, Shenyang 110819
Cite this article:
Juan MU,Dongmei WANG,Yandong WANG. EFFECT OF COOLING RATE AND ASPECT RATIO ON MECHANICAL PROPERTIES OF Ti-BASED AMORPHOUS ALLOY COMPOSITES. Acta Metall Sin, 2015, 51(12): 1435-1440.
Amorphous alloy composite is designed to prevent rapid propagation of shear bands in amorphous phase by introducing the second crystalline phase, which can improve the plasticity of alloy. In situ formed amorphous alloy composites have attracted much interest due to excellent properties and extensive application prospect, especially the dendrite reinforced amorphous alloy composite with excellent tensile plasticity. Recent studies show that the plastic deformation behavior of amorphous alloy composite is not only related to the mechanical properties of the crystalline phase, such as elastic modulus, but also with the size, volume fraction and morphology of the crystalline phase. In addition, the mechanical properties, especially the plastic deformation ability, of amorphous alloys are closely related to topological morphology of the samples, such as aspect ratio. For the amorphous alloy composite, the relationship between mechanical properties and topological morphology of the samples are of interest. In this work, by adjusting preparation process and size of the samples, the effect of cooling rates and aspect ratios on the mechanical properties of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites were systematically studied. As decreasing the cooling rate during the preparation process, the sizes of dendrites in the amorphous alloy composites increases. And the crystalline phase presents evolution from branchlets to coarse dendrite. As the cooling rate decreases, strength of the composite decreases while plasticity increases. Moreover, different from the previous reports, the mechanical properties of amorphous alloy composite are not sensitive to the aspect ratio. It is attributed to the existing of the dendrites phase and deformation-induced phase transformation in the dendrites, which may adjust stress distribution of the amorphous alloy composites during deformation process.
Fund: Supported by National Natural Science Foundation of China (Nos.51301034 and 51434008) and Fundamental Research Funds for the Central Universities (Nos.N141004001 and L1502026)
Fig.1 XRD spectra of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with different diameters
Fig.2 SEM images of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with diameters of 3 mm (a), 5 mm (b) and 8 mm (c)
Diameter
Area
Ti
Zr
Ni
Cu
mm
3
Matrix
41.43
42.46
5.70
10.41
Dendrite
59.42
37.91
0.38
2.29
5
Matrix
43.59
41.88
4.98
9.55
Dendrite
53.33
39.25
2.51
4.90
8
Matrix
40.14
43.07
5.86
10.94
Dendrite
58.58
37.60
1.07
2.75
Table 1 EDS results of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with different diameters
Fig.3 DSC curves of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with different diameters (Tg—glass transition temperature, Tx—on-set crystallization temperature)
Fig.4 Compressive stress-strain curves of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with diameters of 3 mm (a), 5 mm (b) and 8 mm (c) at different aspect ratios H/D (H—height, D—diameter)
Diameter
Tg / ℃
Tx / ℃
Crystallization
/ mm
entropy / ( Jg)
3
340.5
378.2
-33.60
5
362.0
379.5
-29.62
8
356.4
377.1
-29.96
Table 2 Thermal dynamic parameters of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with different diameters gained from DSC curves
Fig.5 Yield strength (a), fracture strength (b) and plastic strain (c) of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with different diameters at various aspect ratios
Fig.6 Variations of mechanical properties of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with diameters of 3 mm (a), 5 mm (b) and 8 mm (c) as a function of aspect ratios
Fig.7 SEM images of fracture surfaces of Ti45.7Zr33Ni2.9Cu5.9Be12.5 amorphous alloy composites with diameters of 3 mm (a), 5 mm (b) and 8 mm (c)
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