The objective of this contribution is to summarise the range of α crystallography and distribution that arises from the β to α transformation and the hot working of α/β alloys and their recrystallisation and relate these features to the slip character of these alloys. α morphology and distribution have been mapped as a function of β stabilizer content and aging temperature. A dominant transgranular grouping of α variants with a common close packed direction characterizes transformation patterns across the entire range of β stabilizer content. Recrystallization during thermomechanical processing in the α/β regime has been studied with the help of fine scale, orientation image mapping techniques. Two distinct recrystallization processes have been identified. The first is associated with the well-known α globularisation process. An alternative recrystallization process has also been described in which newly recrystallized α and β grains form with the Burgers orientation relationship with each other. This process has been called epitaxial recrystallization. The role of transformation and recrystallisation texture on the plasticity of titanium alloys is assessed through quantitative EBSD /TEM based analysis of slip systems in the α phase and slip transfer between the α and β phases.
The performance of ferrite-martensite (DP 600) and ferrite-pearlite (SPFH 590) steels with a similar tensile strength of ∼650 MPa under cyclic loading was investigated. This work presents the high cycle fatigue properties of DP 600 and SPFH 590 steel in the presence and absence of a hole. In presence of the hole, the fatigue strength for both the steels drops significantly, with drop being more for SPFH 590 steel. While the fatigue strength in absence of a hole is a strong function of yield strength of material, the behaviour in presence of the hole depends on the steel microstructure. The presence of martensite in case of DP 600 steel delayed the crack propagation by branching and crack tip blunting. Additionally, martensite also increases the local strain, low angle grain boundary and dislocation density ahead of the crack tip, resulting in an increased amount of plastic deformation and blunting of the crack tip.
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