Microstructures and High Temperature Tensile Properties of As-Aged Mg-6Zn-1Mn-4Sn-(01, 0.5 and 1.0) Y Alloys

Abstract

The microstructures and high-temperature tensile properties of as-aged Mg-6Zn-1Mn-4Sn-(0.1, 0.5 and 1.0) Y (wt.%, ZMT614-Y) alloys were investigated by optical microscopy (OM), X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-temperature tensile tests. The tensile temperatures were 150 °C, 200 °C, 250 °C and 300 °C, respectively. The results showed that the phase compositions of as-aged alloys were α-Mg, α-Mn, MgZn2, Mg2Sn, and MgSnY phases. The Mg2Sn and MgSnY high-temperature phases inhibited grain growth in the heat treatment and tensile processes. The as-aged ZMT614-0.5Y alloy has the best high-temperature mechanical properties, with yield strength (YS), ultimate tensile strength (UTS), and elongation values of 277 MPa, 305 MPa, and 16.7%, respectively, at 150 °C. As the tensile temperature increased to 300 °C, the YS and UTS decreased to 136 MPa and 150 MPa, and elongation increased to 25.5%. The fracture mechanism changed as the tensile temperatures ranged from 150 °C to 300 °C, from the transgranular fracture type at temperatures of 150 °C and 200 °C, to the transgranular and intergranular mixed-mode fracture type when tensile temperatures increased to 250 °C, to an intergranular fracture mechanism at 300 °C.

Review on the Effect of Deep Cryogenic Treatment of Metallic Materials in Automotive Applications

“…Magnesium alloys can be mostly found in racing cars (very light material and contribute to saving fuel), for example, in Porsche 917, 133 kg of its total weight is attributed to components made of magnesium alloys [5] A synopsis of the literature on the non-ferrous alloys exposed to DCT presented in Table 2 provides interesting outcome, demonstrating that not much research has been conducted in the field of DCT in combination with non-ferrous alloys. This is shown by the scarce amount of studies conducted with a much limited amount of different alloys researched in terms of DCT effect [81][82][83][84][85][86]. The overlook of the results verified, that research of non-ferrous alloys is still, more or less at the beginning, even though some studies on non-ferrous alloys were conducted by National Aeronautics and Space Administration (NASA) in 1950s-2000s of aluminum alloys for space industry [87].…”

“…As a consequence, more studies will be promoted in the field of cryogenic treatment and behavior of selected alloys. Observation showed that selected soaking temperatures of applied DCT on non-ferrous alloys is in the range of −163 to −196 • C, being about 10 • C lower than in average used for ferrous alloys in automotive industry [81][82][83][84][85][86]88]. This indicates, that lower temperatures are apparently needed, when dealing with non-ferrous alloys.…”

“…The possible explanation could be in the absence of carbon and the much different phase formation mechanisms found in non-ferrous alloys. Soaking time of experiments is in the most cases longer than 20 h [82,85], but there can be found also shorter holding times, for example, 2, 4, 8, 12, 16 h [82,83,88]. This could also indicate that longer time is needed for improvement of the properties of the non-ferrous alloys compared to ferrous alloys.…”

“…This could also indicate that longer time is needed for improvement of the properties of the non-ferrous alloys compared to ferrous alloys. Cooling and warming rates in conducted studies differs from 0.5 [85] to 20 • C/min [82]. The guidelines for application of DCT on non-ferrous alloys are also spare and are not systematically approached.…”

“…But in other cases properties improvement of metallic materials were insignificant [48,82] or even deteriorated [74,75]. The DCT improves dimensional stability [72,73], resistance to electro-chemical corrosion [72], hardness [3,73,74], wear resistance [3,74,81,85], machining time and machinability [3], impact toughness [47], free energy absorption [74], ductility [83,84] and smooth surface of alloys is improved [82]. Furthermore, it provides more homogeneous and finer distribution of precipitated secondary carbides [53,75].…”