Direct observation of deformation in semi-solid carbon steel

In situ study of granular micromechanics in semi-solid carbon steels

“…In situ synchrotron radiography studies of semi-solid deformation in Al-alloys [13] and steels [18] at 30-60% solid have confirmed the importance of interpreting the material response within a granular mechanics framework. Granular materials are disordered assemblies of macroscopic particles in contact [19] and include soils, powders, and cereal grain in silos.…”

“…Furthermore, semi-solid deformation is not homogeneous at the micro-scale [12,14,15] and strain readily localises [11]. Due to this complexity and multiple simultaneous mechanisms, in the last 5 years various groups have developed techniques to directly observe the deformation mechanisms in situ and link the crystal-scale mechanisms to the macroscopic semi-solid response [13][14][15][16][17][18].…”

Dilatancy in semi-solid steels at high solid fraction

“…Note that the pushplate moves vertically upwards from the bottom right of each image. It can be seen that, as the pushplate intrudes into the sample, the space between the grains increases and fills with liquid, seen in lighter grey in Figure 2 The opening of spaces between the grains as the pushplate shears the sample is the phenomenon of shear-induced dilation or Reynold's dilatancy [27] which is widespread in particulate materials [28][29][30] and has been shown to occur in semi-solid alloys [13,31,32]. This is shown at higher magnification in Figure 3 The shear-induced dilation deformation mechanism can be understood from the group of four grains shown in Figure 4(a) (which is from the region highlighted in Figure 3 The lack of grain-grain cohesion indicates that most grains are separated by liquid films and not coalesced grain boundaries.…”

“…In order to directly image the microstructural response to load, we use synchrotron radiography building on the techniques developed for steel solidification by Yasuda et al [12]. We study deformation under conditions of fully-fed deformation and deformation with inadequate feeding with the following specific aims: (i) to identify and quantify the deformation mechanisms, (ii) to compare the observed mechanisms with those assumed in models of the continuous casting process and those measured in steels at lower solid fraction previously [13][14][15], and (iii) to develop an understanding of how shear deformation can generate macrosegregation and cracking during the final stages of solidification.…”

Kinetics of the δ/γ interface in the massive-like transformation in Fe-0.3C-0.6Mn-0.3Si alloys

“…For example, dendritic solidification of Sn and Al alloys has been reported [4][5]. Recently, the technique has been extended to observe solidification of Fe-C alloys [6][7][8] and deformation of semisolid [9]. Since the in situ observation allows us to know how the solidification and the phase transformation proceed, the technique provides direct and valuable information for modelling microstructural evolution and defect formation.…”