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Because of their excellent combination of strength and ductility, quenching and partitioning (Q & P) steels have a great chance of being added to the third generation of advanced high strength steels. The large ductility of Q & P steels arises from the presence of 10% to 15% of retained austenite which postpones necking due to the transformation induced plasticity (TRIP) effect. Moreover, Q & P steels show promising forming properties with favourable Lankford coefficients, while their planar anisotropy is low due to a weak texture. The stability of the metastable austenite is the key to obtain tailored properties for these steels. To become part of the newest generation of advanced high strength steels, Q & P steels have to preserve their mechanical properties at dynamic strain rates and over a wide range of temperatures. Therefore, in the present study, a low-Si Q & P steel was tested at temperatures from −40 • C to 80 • C and strain rates from 0.001 s −1 to 500 s −1 . Results show that the mechanical properties are well-preserved at the lowest temperatures. Indeed, at −40 • C and room temperature, no significant loss of the deformation capacity is observed even at dynamic strain rates. This is attributed to the presence of a large fraction of austenite that is so (thermally) stable that it does not transform in the absence of deformation. In addition, the high stability of the austenite decreases the elongation at high test temperatures (80 • C). The additional adiabatic heating in the dynamic tests causes the largest reduction of the uniform strain for the samples tested at 80 • C. Quantification of the retained austenite fraction in the samples after testing confirmed that, at the highest temperature and strain rate, the TRIP effect is suppressed.Metals 2020, 10, 509 2 of 22 twinning induced plasticity (TWIP) and austenitic steels. These steels have excellent properties, though their use is limited because they require large amounts of expensive alloying elements such as Ni, Mn and Cr [8][9][10][11]. In recent years, a third generation of AHSS is being developed. Steels which may claim to be part of the third generation are medium to high manganese steels [12][13][14][15], complex phase steels [16], steels produced via severe plastic deformation [17] or ultrafast thermal processing routes [18][19][20][21], and quenched and partitioned (Q & P) steels [22,23].Q & P steels first appeared in literature in 2003 and have gained research interest since then [23]. Q & P steels combine high strength and ductility because of their complex multi-phase microstructure. This microstructure is obtained by imposing a (two-step) thermal cycle to low carbon steel with Si/Al as most the important alloying elements. After initial austenisation, the material is quenched to the quenching temperature situated in between the martensite start (Ms) and martensite finish temperature (Mf). This creates a microstructure of martensite and austenite of equal carbon content. The fractions of both are determined by the quenching temperature ...