Semi‐Solid Processing of Tailored Aluminium‐Lithium Alloys for Automotive Applications

Abstract

This paper describes the development and evaluation of thixoformable Al‐Li‐Mg‐based alloys performed at the collaborative research center SFB 289, RWTH Aachen. Scandium and zirconium were added to AlLi2.1Mg5.5 (A1420) with the aid of DoE (Design of Experiments), and precursor billets were manufactured by pressure induction melting (PIM). To evaluate the thixoformability of the synthesized alloys semi‐solid processed connecting rods were manufactured by the rheo container process (RCP). Subsequent heat treatment raised the mechanical properties to maximum values of tensile strength, 430 MPa, yield strength of 250 MPa, and an elongation to fracture of 13 %. The RCP process was designed for the special requirements of highly reactive alloys. The paper presents the remarkable property and process benefits of the semi‐solid processing of Al‐Li alloys.

Semi-Solid Casting of High-Reactive Wrought Alloys by Means of the Alloy AlLi2.1Mg5.5ScZr (AA1420*)

“…Via heat treatment the mechanical properties of AA1420 * were improved significantly. In this way the tensile strength was increased to over 400MPa, the yield strength up to 250MPa, and the elongation to fracture to an average of 6.4%, almost three times higher than in the thixocast condition, [8]. Chemical analyses showed that the tie rods were manufactured homogeneously, [8].…”

“…In this way the tensile strength was increased to over 400MPa, the yield strength up to 250MPa, and the elongation to fracture to an average of 6.4%, almost three times higher than in the thixocast condition, [8]. Chemical analyses showed that the tie rods were manufactured homogeneously, [8]. To investigate the improvement potentials of the heat treatment, sectioned samples of the connecting rod were solution-annealed (24h at 460°C), quenched in water and subsequently aged for various times in an oil bath at different temperatures (140°C, 160°C, 180°C) at the Swiss Federal Institute of Technology (ETH) Zurich.…”

“…While increasing the ageing temperature, the maximum of hardness (130 HV in each experiment) requires shorter ageing time. In order to achieve a maximum hardness, the following annealing parameters are advisable: 180°C/10h, 160°C/25h or 140°C/>35h, [8]. This revised heat treatment was tested during thixo casting experiments with the modified AA1420.…”

“…350g (A356). Due to the challenging castability, it was appropriate to investigate the difficult to cast aluminium-lithium wrought alloy AA1420 * , [8]. The mould was adjusted regarding the rheological behaviour of semi-solid suspensions.…”

Effects of Process Parameters on the Microstructure and Hardness of Semi-Solid AlSi9Mg Aluminum Alloy Prepared by RAP Process

“…6,7) SSMF is achieved through forming the component by dies at the semisolid temperature based on the semi-solid billets. 8) The fabrication of the semi-solid billet with the small and spherical grains is the guarantee to realize a successful SSMF. Many methods have been proposed to prepare the high-quality semi-solid billets, including the mechanical and electromagnetic stirring, 9) gas-induced semi-solid process, 10) cooling slope, 11) strain-induced melting activation (SIMA), 12) mechanical vibration, 13) and recrystallization and partial melting (RAP).…”