Thixoforming : Semi-solid Metal Processing

Figure 9.45 MAGMAsoft simulation: comparison between steel
core temperature: 60 and 300 C. The simulation shows the
displacement of the hotspot.
Twelve tie rods were cast and consecutively numbered T1–T12. The samples
T1–T3 were not further treated. All other samples were heat treated at the IME
(Department for Process Metallurgy and Metal Recycling of RWTH Aachen University)
under an argon atmosphere. First, all nine samples were solution annealed for
24 h. With reference to the improvement tests at the ETH Z€urich, the samples were
subsequently aged: the samples T4–T6 were aged for 10 h at 180 C, T7–T9 for 25 h at
160 C and T10–T12 for 35 h at 140 C. As shown in Figure 9.44, flat bar tension
specimens were taken from both sides of the double-T beam of the tie rods (six
samples per treatment condition) and tensile tested. The results are illustrated by
means of a bar diagram in Figure 9.47.
Figure 9.46 Hot tearing at the large bearing point. From left to
right: a decreasing steel core temperature results in a decreasing
hot tear tendency.
9.4 Rheoroutej361