Pore behaviour during semi-solid alloy compression: Insights into defect creation under pressure

Dilatancy in semi-solid steels at high solid fraction

“…In the case of thin sample radiography where the sample has a large free surface area and no liquid reservoir, the decreasing liquid pressure due to inadequate or insufficient liquid flow to the expanding liquid-filled interstices causes the drawing-in of menisci from the sample surface in a cracklike manner. In continuous casting, there is a much smaller surface area to volume ratio and it is likely that unfed dilatancy will be accommodated by other mechanisms, such as the opening of internal pores (which has been demonstrated previously in semi-solid Al alloys by some of the authors [44]) or the formation of internal cracks. Additionally, the work done in sucking liquid into the expanding interstices of a low-permeability mush is expected to lead to 'dilatant hardening' as occurs in partially-molten rock mechanics [45], whereby the suction in the liquid increases the effective normal stress on the expanding interstices/internal cracks and continuing deformation requires higher stresses.…”

Semisolid microstructural evolution of (CNTs + Sip)/AZ91D powder compacts prepared from powders by cold pressing and remelting

“…The densification rate increased gradually over the heating period. Pore filling is known to be an essential process for densification and is obviously determined by the amount of liquid in the powder compact and the balance between the ambient pressure, the liquid pressure, and the pressure exerted by the liquid meniscus due to tension at the gas-liquid interface [28,29]. As the liquid fraction increased, liquid flow was increasingly sufficient to fill in the interstitial spaces among the primary particles, eliminating the small internal preexisting pores and increasing the relative density.…”

Engineering Science at the I12 Beamline at Diamond Light Source

“…The deformation mechanics of this mush is difficult to understand, as many effects occur concurrently, such as development solid networks between grains, rearranging and shear of individual grains, development of force chains, cracking of grains, opening of internal volumes, and the associated liquid motion [2,3]. The dynamics of semi-solid materials during deformations, such as tensile [4], compression [5,6], indentation [3,7], or extrusion [8], could be studied using in-situ tomography (Figure 1).…”