Influence of Initial Microstructure on the Strengthening Effect of Extruded Mg-8Sn-4Zn-2Al Alloys

doi:10.1007/s40195-017-0673-5

Abstract

Abstract:

The Mg-8Sn-4Zn-2Al (TZA842, in wt%) alloys with different initial microstructure (as-cast-AC and homogenization treatment-HT) subjected to hot extrusion. Also, the strengthening responses to AC and HT for the extruded TZA842 alloys were reported. The results revealed that the alloy subjected to HT shows finer grain size, more homogenous microstructure and weaker basal texture than those of counterpart subjected to AC. In addition, compared with TZA842-AC alloy, precipitates were finer and uniformly dispersed in TZA842-HT owing to the utilization of HT. Moreover, the TZA842-HT alloy showed higher yield strength of 200 MPa, ultimate tensile strength of 290 MPa and elongation (EL) of 17.9% than those of TZA842-AC, which was mainly attributed to the combined effects of grain boundary strengthening, precipitation strengthening, solid solution strengthening and weak texture. Strengthening mechanism for both alloys was discussed in detail.

Key words: Mg-Sn alloy, Extrusion, Microstructure, Tensile property, Strengthening mechanism

Yang Bai, Wei-Li Cheng, Shi-Chao Ma, Jun Zhang, Chen Guo, Yao Zhang. Influence of Initial Microstructure on the Strengthening Effect of Extruded Mg-8Sn-4Zn-2Al Alloys[J]. Acta Metallurgica Sinica (English Letters), 2018, 31(5): 487-495.

Figures/Tables 9

Fig. 1 XRD patterns of the TZA842 alloys: a as-cast, b as-homogenized, c TZA842-AC, d TZA842-HT

Fig. 2 OM and SEM images of TZA842 alloys prior to extrusion in different states: a, c as-cast b, d as-homogenized

Table 1 EDS results of TZA842 alloys

Position	Element				Possible compound
Position	Mg	Sn	Zn	Al	Possible compound
A	72.8	27.2	-	-	α-Mg + Mg₂Sn
B	60.1	39.9	-	-	Mg₂Sn
C	39.7	-	44.5	15.8	Mg₃₂(AlZn)₄₉
D	51.1	48.9	-	-	Mg₂Sn
E	54.1	45.9	-	-	Mg₂Sn
F	40.9	-	43.1	16.0	Mg₃₂(AlZn)₄₉
G	59.0	41.0	-	-	Mg₂Sn
H	41.3	-	42.5	16.2	Mg₃₂(AlZn)₄₉

Fig. 3 OM images of extruded TZA842 alloys in different states: a, c TZA842-AC b, d TZA842-HT

Table 2 Microstructural characteristics and tensile properties of extruded TZA842 alloys

State	Microstructure				Tensile properties
State	f _DRX (%)	d _DRX (μm)	f _P (%)	d _P (μm)	YS (MPa)	UTS (MPa)	EL (%)	n
TZA842-AC	93.3	3.71	2.3	0.33	145 ± 3	216 ± 4	15.2 ± 0.3	0.19
TZA842-HT	98.2	1.78	10.7	0.23	200 ± 2	290 ± 2	17.9 ± 0.2	0.24

Fig. 4 SEM images of extruded TZA842 alloys: a, d TZA842-AC, b, e TZA842-HT, c particle size distribution in both alloys

Fig. 5 The (0002) pole figures of the extruded alloys: a TZA842-AC and b TZA842-HT

Fig. 6 a Tensile engineering stress-strain curves and b work-hardening rate (θ) as function of net flow stress (σ - σ 0.2) of extruded TZA842 alloys

Fig. 7 SEM images of the extruded alloys: a TZA842-AC and b TZA842-HT

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