Effects of Cooling Rate and Component on the Microstructure and Mechanical Properties of Mg-Zn-Y Alloys

doi:10.1007/s40195-014-0140-5

Abstract

Abstract:

The microstructure and mechanical properties of Mg-6Zn-1Y and Mg-6Zn-3Y (wt%) alloys under different cooling rates were investigated. The results show that the second dendrite arm spacing (SDAS) of Mg-6Zn-1Y and Mg-6Zn-3Y is reduced by 32 and 30% with increasing cooling rates (R _c) from 10.2 to 23 K/s, which can be predicted using a empirical model of $$ {\text{SDAS}} = 68R_{\text{c}}^{ - 0.45}$ $ and $$ {\text{SDAS}} = 73R_{\text{c}}^{ - 0.45} $$, respectively. The compressive strength of both alloys increases with increasing the cooling rate, which is attributed to the increase of volume fraction (V _f) of secondary phases under high cooling rate. The interaction of the cooling rate and component with SDAS has been theoretically analyzed using interdependence theory.

Key words: Mg-Zn-Y alloys, Microstructural characterization, Compressive strength, Cooling rate, Interdependence theory

Shuang Shao, Yong Liu, Chun-Shui Xu, Ying-Xuan Xu, Bin Wu, Xiao-Shu Zeng, Xian-Feng Lu, Xiang-Jie Yang. Effects of Cooling Rate and Component on the Microstructure and Mechanical Properties of Mg-Zn-Y Alloys[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(1): 7-14.

Figures/Tables 10

Fig.1 a The dimension of the ingot; b the accurate position of section A, B, C; c the cooling curves and average cooling rates of section A, B, C

Fig.2 XRD patterns of Mg-6Zn-1Y a and Mg-6Zn-3Y b

Fig.3 DSC curves of Mg-6Zn-1Y and Mg-6Zn-3Y under different cooling rates

Fig.4 Microstructures of Mg-6Zn-1Y a-c and Mg-6Zn-3Y d-f under different cooling rates: a, d 10.2 K/s, b, f 15.7 K/s, c, e 23 K/s

Table 1 The value of second dendrite arm spacing (SDAS) and volume fraction of secondary phase (V f) of Mg-6Zn-1Y and Mg-6Zn-3Y alloys under different cooling rate

Cooling rate (K/s)	Mg-6Zn-1Y		Mg-6Zn-3Y
Cooling rate (K/s)	V _f (%)	SDAS (μm)	V _f (%)	SDAS (μm)
10.2	8.6	25.1 ± 2	8.9	21.8 ± 2
15.7	15.5	21 ± 2	17.1	18.5 ± 2
23	20.7	17 ± 2	25.7	15.2 ± 2

Fig.5 Compression properties of alloys Mg-6Zn-1Y a, Mg-6Zn-3Y b, and their micro-hardness variation with the cooling rates c

Fig.6 SDASs of Mg alloys as a function of cooling rate

Table 2 The fitting parameters of different Mg alloys

Material	α	n
Mg-6Zn-1Y	68	-0.45
Mg-6Zn-3Y	73	-0.45
AZ91D [25]	49	-0.42
Mg-1Zn-2Y ^[²⁶^]	37.1	-0.33

Table 3 The parameters used in the calculation of interdependence theory

Parameter	Value
D	1 × 10^-12 m²/s [34]
Γ	1.52 × 10^-7 km [33]
m _Zn	4.9 K/wt%
k _Zn	0.94
m _{Y (Mg-6Zn-1Y)}	1.35 K/wt%
k _{Y (Mg-6Zn-1Y)}	0.78
m _{Y (Mg-6Zn-3Y)}	1.44 K/wt%
k _{Y (Mg-6Zn-3Y)}	0.76

Fig.7 Experimental and theoretical SDASs of Mg-6Zn-1Y and Mg-6Zn-3Y alloy

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