Papers by Author: Chad W. Sinclair

Abstract: Several studies have shown that recrystallization of cold rolled martensite results in low carbon steels with very fine microstructures. Correspondingly, these materials exhibit promising combinations of strength and elongation. Most of the work on this processing route has focused on low carbon steels (0.1-0.2wt% carbon) where the interstitial content may play an important role in the microstructure refinement. In this note we describe experiments performed on a low interstitial stainless steel containing 0.02wt%C. It has been possible to achieve materials with high strengths (UTS > 1 GPa) and significant uniform elongation (> 8%), however, the microstructures associated with these properties are very different from those previously reported for low carbon steels.

Abstract: The comparative effectiveness of solute Nb and NbC particles at impeding grain boundary motion is treated theoretically. It is shown that, for a steel containing ~0.05 at% Nb (~0.1 wt%Nb), under typical recrystallization conditions, solute Nb is more effective in the ferrite, whereas in the austenite, depending on the exact recrystallization temperature, either solute Nb or NbC precipitates may be more effective.

Abstract: The work hardening behavior of an Al-3Cu-0.05Sn (wt %) alloy was studied using tensile tests and Bauschinger tests. Emphasis is placed on the influence of the precipitation state (number density, size distribution and volume fraction) and separating the isotropic and kinematic components of the work hardening.

Abstract: The addition of scandium severely retards the recrystallization of Al-Sc alloys when it is present in the form of fine Al3Sc precipitates. Though many studies have focused on the role of Al3Sc in the deformation and recrystallization of pre-aged or hot deformed Al-Sc alloys, recent studies on the annealing response of solutionized and cold rolled material have shown various possibilities for microstructural stability depending on the relative kinetics of precipitation and recrystallization. In this study, the microstructural evolution of solutionized and cold rolled Al- 2.9wt%Mg-0.16wt%Sc has been followed in order to evaluate the role of imposed strain and annealing temperature on the recrystallization kinetics.

Abstract: Despite extensive studies on the aging behaviour of Al3Sc containing alloys, the underlying mechanism of the precipitation strengthening is still not well understood. In particular, the transition radius at which particles become non-shearable is not known. In this work, the work hardening behaviour of an Al-2.8Mg-0.16Sc (wt%) alloy has been characterized for different stages of aging and the corresponding slip line features at the surface of strained specimens have been examined using Nomarski interference contrast. Moreover, the work hardening behaviour is discussed in the framework proposed by Kocks, Mecking and Estrin. It is proposed that changes in macroscopic work hardening behaviour can be used as a signature of the shearable/non-shearable transition.

Abstract: The observation of inhomogeneous, ‘sluggish’ recrystallization in ferritic steels has been extensively documented and discussed, particularly with reference to low carbon steels. Stabilized ferritic stainless steels are also prone to this phenomenon and, in many cases, exhibit the effect more strongly than their carbon counterparts. The situation for stainless steels is exacerbated in part by the topology of the cold rolled microstructure, which is composed of highly elongated and layered grains. In this work an attempt has been made to probe the key features of this process by means of a two-dimensional vertex simulation. Key microstructural characteristics such as subgrain and grain size, topology, misorientation and energy are varied in these simulations in an attempt to elucidate the mechanisms responsible for the final recrystallization. These simulations are compared and contrasted with experimental observations from the recrystallization of an AISI409 stainless steel.

Abstract: Obtaining optimal mechanical properties for highly formable ferritic stainless steel sheet requires careful control over recrystallization and texture. This is, in some cases, hampered by the slow approach to final recrystallization associated with the disappearance of deformed grains with particular orientations. The important mechanical properties for formability (e.g. the yield strength and r-value) are thus strongly dependent on the final few percent recrystallization. In this study, it has been attempted to correlate the microstructure and texture of ferritic stainless steel sheet to its mechanical properties as measured in uniaxial tension. It is shown that careful consideration of the evolution of texture and microstructure with recrystallization may explain the observed trends.