TAB.3 ROOM TENSILE PROPERTIES OF EXTRUDED MG‐5SN‐2SI‐2SR ALLOY IN DIFFERENT CONDITIONS Conditions
σ0.2/MPa
σb/MPa
δ/%
Extrusion
202.3
240.6
9.0
T4
195.6
225.7
8.2
T5
210.9
257.0
12.5
T6
206.1
248.1
12.4
TAB.4 HOT TENSILE PROPERTIES OF EXTRUDED MG‐5SN‐2SI‐2SR ALLOY IN DIFFERENT CONDITIONS(150℃) Conditions
σ0.2/MPa
σb/MPa
δ/%
Extrusion
103.7
139.0
12.5
T4
101.0
133.6
9.9
T5
107.7
149.2
15.9
T6
105.1
144.0
16.7
Fig.4 shows the tensile fracture morphology of extruded Mg-5Sn-2Si-2Sr alloy in different conditions. It can be seen that the tensile fracture have mixed feature of cleavage and quasi cleavage. The fracture surface has some cleavage planes, cleavage steps and river patterns, there are also a few tearing ridges and few dimples exist. It can be seen from Fig.4a, Fig.4b and Fig.4c, the fracture morphology of as-extruded, T4 state and T6 state is similar. The fracture surface has a large number of tiny quasi-cleavage planes, a few tearing ridges and few dimples. However, fracture morphology of T5 state is quite different from others, it has many bright tearing ridges and obvious river patterns. The number of tiny quasi-cleavage plane decrease which indicates that T5 state alloy has good tensile strength.
a
b
c
d
FIG. 4 TENSILE FRACTURE MORPHOLOGY OF EXTRUDED MG‐5SN‐2SI‐2SR ALLOY AT ROOM TEMPERATURE (A) AS‐EXTRUDED; (B) T4 TREATMENT; (C) T5 TREATMENT; (D) T6 TREATMENT
In order to explore the heat resistance of magnesium alloys in this series, this article has also studied the elevated tensile properties of extruded Mg-5Sn-2Si-2Sr alloy. Fig.5 shows the tensile fracture morphology of extruded Mg-5Sn-2Si-2Sr alloy at elevated temperature in different conditions. It can be seen that the elevated fracture mode of extruded Mg-5Sn2Si-2Sr alloy at 150℃ is mixed fracture of brittle and ductile. The fracture surface has some cleavage planes, cleavage steps and river patterns. Compared with the fracture surface at room temperature, the fracture surface at elevated temperature has more dimples indicate that the ductility increase obviously at high temperature. It can be seen from Fig.5a and Fig.5b, the fracture morphology of as-extruded, T4 state is similar. The fracture surface has quasi-cleavage planes, tearing ridges and dimples. Fig.5c shows that the fracture surface of T5 state has many bright tearing ridges and the cleavage plane become smaller which indicate that T5 state alloy has good tensile strength. Fig.5d shows that the number of the dimple on the T6 state fracture surface increase obviously and there are also many bright tearing ridges exist which indicate that T6 state alloy has good ductility. 22 http://www.ivypub.org/rms/