Orientation-Dependent Developments in Misorientation and Residual Stress in Rolled Aluminum: The Defining Role of Dislocation Interactions

Orientation-dependent developments in misorientation and residual stress, in rolled aluminum, were quantified experimentally and simulated numerically. The latter involved analysis using a crystal plasticity finite element model, accounting for anisotropies in slip system hardening but neglecting near-neighbor interactions, and discrete dislocation dynamics of the single crystals. Both were successful in capturing the experimental patterns of orientation dependence. Numerical simulations, without slip transfer across the neighboring grains, thus established the defining role of dislocation interactions in establishing orientation-sensitive microstructural evolution.     

Relating Residual Stress and Substructural Evolution During Tensile Deformation of an Aluminum-Manganese Alloy

Interrupted tensile tests were coupled with ex situ measurements of residual stress and microtexture. The residual stress quantification involved measurements of six independent Laue spots and conversion of the interplanar spacings to the residual stress tensor. A clear orientation-dependent residual stress evolution emerged from the experiments and the numerical simulations. For the orientations undergoing negligible changes in ρ _GND (density of geometrically necessary dislocation), the residual stress developments appeared to be governed by the elastic stiffness of the grain clusters. For the others, the evolution of the residual stress and ρ _GND exhibited a clear orientation-dependent scaling.     

Development of Texture and Microstructure During Cold Rolling and Annealing of a Fe-Based Shape Memory Alloy

Texture evolution and microstructural changes during cold rolling and annealing of Fe-14Mn-6Si-9Cr-5Ni shape memory alloy have been investigated. The starting solution-annealed material has a nearly random texture with microstructure composed of equiaxed austenite grains with ε martensite plates inside. Cold rolling induces a strong alloy type texture with Brass {011}〈211〉 and Goss {011}〈100〉 as major components. Annealing of the cold-deformed material produces a nearly random texture. The microstructural investigation reveals that with increase in cold deformation, the amount of stress-induced ε and α′ martensite volumes increase. The electron back-scattered diffraction (EBSD) phase mapping shows that reversion of the ε martensite begins only after recrystallization sets in at a temperature of 1073 K.     

Development of Multiphase Microstructure with Bainite, Martensite, and Retained Austenite in a Co-Containing Steel Through Quenching and Partitioning (Q&P) Treatment

The quenching and partitioning (Q&P) treatment of steel aims to produce a higher fraction of retained austenite by carbon partitioning from supersaturated martensite. Q&P studies done so far, relies on the basic concept of suppression of carbide formation by the addition of Si and/or Al. In the present study Q&P treatment is performed on a steel containing 0.32 C, 1.78 Mn, 0.64 Si, 1.75 Al, and 1.20 Co (all wt pct). A combination of 0.64 Si and 1.75 Al is chosen to suppress the carbide precipitation and therefore, to achieve carbon partitioning after quenching. Addition of Co along with Al is expected to accelerate the bainite transformation during Q&P treatment by increasing the driving force for transformation. The final aim is to develop a multiphase microstructure containing bainite, martensite, and the retained austenite and to study the effect of processing parameters (especially, quenching temperature and homogenization time) on the fraction and stability of retained austenite. A higher fraction of retained austenite (~13 pct) has indeed been achieved by Q&P treatment, compared to that obtained after direct-quenching (2.7 pct) or isothermal bainitic transformation (9.7 pct). Carbon partitioning during martensitic and bainitic transformations increased the stability of retained austenite.     

Morphology-Dependent Hardness of Cr<Subscript>7</Subscript>C<Subscript>3</Subscript>-Ni-Rich Alloy Composite <Emphasis Type="Italic">vs</Emphasis> Orientation Independent Hardness of Cr<Subscript>7</Subscript>C<Subscript>3</Subscript> Primary Phase in a Laser Clad Microstructure

Microstructural evolution with superheating was studied in chromium carbide-nickel coatings deposited by laser cladding. At lower superheating, selective growth of 〈0001〉 direction from the high density of Cr₇C₃ grains nucleated resulted in a columnar structure with (0001) texture. Increased superheating lead to the loss of columnar structure as well as the (0001) texture. The hexagonal Cr₇C₃ showed an unusual isotropic nanoindentation hardness evidently correlated with its low c/a ratio. However, the rod-like morphology of the carbide dendrites resulted in significant anisotropy in the hardness of the composite.     

Sources of recrystallized grains and their contributions in recrystallization of an AA3104 aluminium alloy

The hot rolled AA3104 ingot was cold rolled to 40%, 66%, 80% and 90% reductions. The cold rolled sheet was subsequently recrystallized at two different annealing temperatures of 573 K and 773 K. The bulk texture developments, both deformation and subsequently after recrystallization, were measured by X-ray ODFs (orientation distribution function), while recrystallized (and in few cases the partially recrystallized or recovered) samples were studied by SEM-EBSD (scanning electron microscope based electron backscattered diffraction).     

The Defining Role of Micro-fissures on the Mechanical Behavior of Laser-Welded Fully Austenitic Stainless Steel

Metallurgical and Materials Transactions A - Laser-welded fully austenitic stainless steel (AISI 316LN) weldments revealed the presence of micro-fissures. They appeared at the grain boundaries,...     

Snoek-Dominated Internal Friction Response in bcc Steel: Relating Experiments With a Multi-scale Atomistic Computational Framework

Metallurgical and Materials Transactions A - Internal friction is often sensitive to microstructural features. However, there is a clear absence of rational approach for decoupling internal...