Abstract
The high-temperature mechanical properties of a 4.5% Al-containing δ-transformation-induced plasticity (TRIP) steel were studied by using the Gleeble 3500 thermomechanical simulator. The zero ductility temperature (ZDT) and the zero strength temperature (ZST) were measured, and the brittle zones were divided. The phase transformation zone was determined by differential scanning calorimetry (DSC). The temperature of the phase transformation and the proportion of the phase were calculated by the Thermo-Calc software. The ZDT and the ZST of the 4.5% Al-containing δ-TRIP steel are 1355 and 1405 °C, respectively. The first brittle zone and the third brittle zone of the steel are 1300–1350 °C and 800–975 °C, respectively. The reason for the embrittlement of the third brittle zone of the 4.5% Al-containing δ-TRIP steel is that the α-ferrite formed at the austenite grain boundary causes the sample to crack along the grain boundary under stress. The ductility of the 4.5% Al-containing δ-TRIP steel decreases first and then increases with the increase of the α-ferrite. When the proportion of the α-ferrite reaches 37%, the reduction of area (RA) of the 4.5% Al-containing δ-TRIP steel is reduced to 44%. The 4.5% Al-containing δ-TRIP steel has good resistance to the high-temperature cracking.
Highlights
Transformation-induced plasticity (TRIP) steel refers to ultrahigh-strength steel that is ductility-elevated due to gradual martensitic transformation processes in steel structures
When there is a high content of Al in alloying elements, it is found that, during the solidification process, the δ-ferrite does not participate in the reaction and remains in the whole temperature range, so it is named δ-TRIP steel
Between 700 and 950 ◦ C, σmax decreased with temperature, while the decreasing speed of the σmax at the temperatures above 950 ◦ C was significantly slower
Summary
Transformation-induced plasticity (TRIP) steel refers to ultrahigh-strength steel that is ductility-elevated due to gradual martensitic transformation processes in steel structures. Δ-TRIP steel, due to its low density, a product of ultimate tensile strength (UTS) and total elongation (TE) (up to 23 GPa·%) similar to the third generation of advanced high-strength steels (AHSS), and excellent welding properties, is expected to become the materials of automobile safety parts and structural parts [1,2]. Found an alloy (its precise composition is Fe–0.4C–0.5Mn–0.2Si–0.5Cr–3.5Al wt %), having a density of 7.455 × 103 kg/m3 , is approximately 5% lighter than that without the aluminum addition, which has a density of 7.8145 × 103 kg/m3. Abedi et al [4] found a duplex low-density steel with an exact chemical composition of Fe–17.5Mn–8.3Al-0.74C–0.14Si (wt %), having a density of 6.8 × 103 kg/m3. The measurement shows that the density of a 4.5% Al-containing δ-TRIP steel is 6.8325 × 103 kg/m3 , which is
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