Study on the Microstructure and Mechanical Property of High Strength Mg-Nd-Zn-Zr Alloy

Abstract

The microstructure and mechanical properties of Mg-3wt％Nd-0.2wt％Zn-0.4wt％Zr alloy in as-cast, solution-treated and solution-treated + peak-aged were investigated. The alloy had a cast structure with large intergranular Mg12Nd phase between the α-Mg matrix. After solution-treated, the intergranular Mg12Nd phase disappeared and lots of small Zr-containing particles distributed inside the grains. Small plate-like phases precipitated inside the grains strengthened the alloy to a high level after peak-aged at 200°C for 16 hours: the ultimate strength of the alloy up to 305 MPa, with considerable elongation rate 11%, and yield strength 140 MPa. The peak-aged samples also had good creep resistance, with strain rate less than 0.2% after 120 hours creep test under the condition of 110 MPa at 200°C. The minimum creep rate was about 4.64×10-9. The alloy had different fracture pattern in different states: as-cast state, intergranular fracture was the key pattern to failure; after solution-treated, the fracture pattern turned to cleavage transgranular fracture; after peak-aged, the alloy had a mixed fracture pattern of transgranular and intergranular, in which transgranular was the main style.

Zr-Containing Precipitates in Mg-3wt%Nd-0.2wt%Zn-0.4wt%Zr Alloy during Solution Treatment at 540°C

“…Mg-RE alloy always contain 0.4-0.6wt% zirconium as grain refiner, such as WE43, WE54 [4]. With 0.2 wt% Zn and 0.4 wt% Zr added to Mg-3wt%Nd, high strength Mg-Nd-Zn-Zr alloy is got [5]. Mg-RE alloy are usually used as T6 state [4].…”

Comprehensive study of phase transformation in age-hardening of Mg–3Nd–0.2Zn by means of scanning transmission electron microscopy

“…%) and low solubility at room temperature (~ 100 ppm), which make it suitable for potential age hardening [8]. The strength of age-hardened Mg-Nd alloys can be further enhanced through solid solution strengthening by controlled addition of third element such as zinc (Zn) [9,[10][11][12][13][14]. Researches have shown that addition of 0.2 wt.…”

“…% Zn to Mg-3 Nd wt. % alloy improves the mechanical properties through mainly solid solution strengthening mechanism [8,[12][13][14][15][16][17][18][19].…”

Effect of Y content on microstructure and mechanical properties of Mg–2·4Nd–0·2Zn–0·4Zr alloys

“…[2][3][4] Addition of trace amounts of element Zn to Mg-Nd alloy could further increase its peak aged hardness. [5][6][7] With increases in demand, the development of higher mechanical properties of Mg-Nd alloy is proposed. Recently, it has been reported that adding the abundant heavy RE such as Gd to Mg-Nd alloy shows superior mechanical properties.…”

“…It is reported that Mg–Nd alloys have significant strengthening effect at room and high temperature 2 – 4. Addition of trace amounts of element Zn to Mg–Nd alloy could further increase its peak aged hardness 5 – 7. With increases in demand, the development of higher mechanical properties of Mg–Nd alloy is proposed.…”