Abstract
The microstructure evolution and mechanical properties of recently developed die-cast Al-Si-Mg-Mn alloys were investigated. CALPHAD modelling, based on the thermodynamic database, was carried out to design Al-Si-Mg-Mn alloys with different solid fractions of the eutectic mixture. Experimental results confirmed that the new Al-Si-Mg-Mn alloys have excellent yield strength of 230–280 MPa, ultimate tensile strength of 340–370 MPa and elongation to fracture of 2.3–4.3% from the standard tensile samples under as-cast condition. The as-cast microstructure consists of α-Al, α-AlFeMnSi, binary eutectic (Al + Mg2Si) and ultrafine quaternary eutectic (Si + α-Al + Mg2Si + π-AlFeMnSiMg). The high strength is induced by the formation of multi-scale eutectic mixtures and fine α-AlFeMnSi particles. The newly designed Al-Si-Mg-Mn alloys offer 20–50% increase in yield strength with good ductility, as compared with the commercially available die-cast aluminium alloys.
Highlights
High-pressure die casting (HPDC) has been widely used for the production of automotive components with many advantages including good surface finish, high dimensional accuracy and excellent Alloy Alloy system Tensile strength /MPa Yield strength Shear strengthElongation /%in 50 mm Al-Si Al-Si-Cu B390 Al-Si-Cu-Mg
The HPDC process is a two-stage solidification process, where some phases partially solidified in the shot sleeve at a very slow cooling rate and rest of liquid solidified in the die cavity at a very high cooling rate [25]
Two types of α-Al phases were observed in alloy A and alloy B, and α1-Al solidified in the shot sleeve has a larger size, while much finer α2-Al forms in the die cavity
Summary
High-pressure die casting (HPDC) has been widely used for the production of automotive components with many advantages including good surface finish, high dimensional accuracy and excellent. The multicomponent TiNbCoCuAl alloy with an ultrafine eutectic microstructure was developed by Okulov et al [13] Such multicomponent alloy exhibits a combination of good strength and high ductility. The development of multicomponent eutectic systems for die-cast aluminium alloys provides a potential route to enhance the yield strength beyond 200 MPa with reasonable elongation to fracture. The purpose of current work is to design multicomponent aluminium based die-cast alloys with yield strength in excess of 200 MPa without the addition of Cu or Zn. Since ternary Al-Si-Mg alloys, such as A356, A357 and A360, exhibit good mechanical properties, age hardening response, excellent castability, low density and good weldability [17,18]. The quaternary Al-Si-Mg-Mn eutectic system was selected for the development of high strength die-cast aluminium alloys using schematic studies of the microstructural evolution and tensile mechanical properties
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