Evaluation of Magnesium Die-Casting Alloys for Elevated Temperature Applications: Microstructure, Tensile Properties, and Creep Resistance

Abstract

Several families of magnesium die-casting alloys have been developed to operate at the elevated temperatures experienced in automotive powertrain applications. Most alloys are based on the Mg-Al system with alloying additions such as silicon, strontium, calcium, and rare earth elements (RE), although alloys with RE as the primary alloying constituent are also considered. This work presents an evaluation of the tensile properties and creep resistance of the most common magnesium die-casting alloys, in conjunction with the analysis of microstructure. The alloys investigated include AS31 (Mg-3Al-1Si), AJ52 (Mg-5Al-2Sr), MRI153A (Mg-9Al-1Ca-0.1Sr), MRI153M (Mg-8Al-1Ca-0.3Sr), MRI230D (Mg-6.5Al-2Ca-1Sn-0.3Sr), AXJ530 (Mg5Al-3Ca-0.2Sr), AE42 (Mg-4Al-2RE), AE44 (Mg-4Al-4RE), and AM-HP2+ (Mg-3.5RE-0.4Zn). It is shown that, among the various alloys evaluated, MRI230D, AXJ530, and AM-HP2+ have higher yield strength than the Al alloy A380, but the ductility is relatively low at room temperature for these alloys. In contrast, AS31 and the AE series alloys have very good room temperature ductility, but their yield strength is lower than that of A380. In terms of creep resistance, MRI230D, AXJ530, AE44, and AM-HP2+ are all comparable to the Al alloy counterpart at 423 K and 448 K (150°C and 175°C). Microstructural factors that are most important to the strength and creep resistance of the Mg die-casting alloys are discussed.

Compressive Creep Behavior of High-Pressure Die-Cast Aluminum-Containing Magnesium Alloys Developed for Elevated Temperature Applications

“…Some of the creep resistant alloys investigated in this paper are die cast specimens previously investigated by Zhu et al (2015). The alloys are AE42, AE44-2, AE44-4, and MRI230D.…”

“…In contrast to Zhu et al (2015), the creep tests were not carried out under tensile stress but under compressive stress. This is the loading direction which represents the more common load case for cast light metals.…”

Mechanical Properties of Thixoforged In Situ Mg2Sip/AM60B Composite at Elevated Temperatures

“…However, the rapid loss of strength at temperatures above 120 • C limits their extended applications [2]. In order to solve this problem, several new heat resistant magnesium alloys have been recently developed [3]. The design in heat resistant magnesium alloys mainly abides by the following ideas: strengthening the α-Mg matrix or/and limiting the cross-slip of dislocations and migration of the grain boundary [4].…”

“…The tensile testing was conducted in a universal material testing machine with a heating device, of which the temperature control precision is ±1 • C. The tensile specimen was heated at the setting temperature for 10 min, and then the test was conducted. In view of the servicing temperature of the magnesium alloys [2,3], which is no more than 300 • C, the tensile testing was carried out under the temperatures of 25 (room temperature), 100, 150, 200, 250, and 300 • C at cross head speeds of 1.0 mm·s −1 , and at cross head speeds of 0.1, 0.5, 1.5, and 2 mm·s −1 under 200 • C, respectively. The corresponding initial strain rates were 0.01, 0.05, 0.1, 0.15, and 0.2 s −1 .…”

Comportamiento microestructural de una fundición de magnesio puro con control en la temperatura de solidificación

“…El magnesio posee una estructura cristalina hexagonal compacta dando lugar a una limitada ductilidad, la cual puede ser mejorada con la adición de elementos como aluminio, zinc, manganeso, entre otros [3][4][5][6] , así como su resistencia mecánica y al creep pueden ser aumentadas considerablemente con adición de aluminio, zinc y algunas tierras raras [6][7][8]. Aunque la producción del magnesio ha aumentado hasta en un 80% en las últimas décadas [1], su manipulación se considera peligrosa debido a su punto de ignición durante los procesos de fundición lo que podría causar algún accidente.…”