An Fe-23Cr-8.5Ni alloy was used as a model material to study the grain size effect on the mechanical behavior of metastable duplex metal. Alloy samples with different grain sizes ranging from 0.1 to 2 μm were prepared by cold-rolling and annealing. A structural refinement to about 0.1 μm results in a high yield strength but very limited ductility. A significant improvement of ductility occurred at the grain size of about 0.4 μm. A further increase in grain size results in a decreased strength and a slightly improved ductility. The alloy with a grain size of about 0.4 μm exhibits an excellent combination of strength and ductility, where the yield strength and tensile elongation are increased up to 738 MPa and 29% as compared to 320 MPa and 33% of a coarse-grained (about 2 μm) sample, respectively. The origin of the excellent mechanical properties was attributed to the unique deformation characteristics associated with the transformation induced plasticity and the development of back stress.

Hetero-deformation induced (HDI) stress and the effect of microstructural morphology on it were investigated in a near-alpha titanium alloy featuring lamellar and equiaxed initial microstructures. The development of HDI stresses were confirmed in the two types of microstructures under tensile tests. While both microstructures exhibit comparable HDI stress magnitudes during initial tensile deformation, the equiaxed one demonstrates obviously enhanced HDI strain hardening compared to its lamellar counterpart as deformation progressed. Two factors are mainly responsible for the observed divergence in HDI stress evolution between the two microstructures. First and foremost is the surface-to-volume ratio of phase interface (sV), where the equiaxed structure shows significantly higher sV than its lamellar counterpart, which can offer more potential sites and better spatial interconnectivity of phase interfaces for GNDs development. The other factor is the microstructural size scale, in which the average layer thickness of the lamellar structure is considered being too small, as compared to the average grain diameter in the equiaxed one, to provide sufficient space for GND pileups to fully develop, which limits HDI strain hardening. This finding provides critical insights into microstructural design strategies for optimizing the development of HDI stress.

Hetero-deformation induced (HDI) stress and the effect of microstructural morphology on it were investigated in a near-alpha titanium alloy featuring lamellar and equiaxed initial microstructures. The development of HDI stresses were confirmed in the two types of microstructures under tensile tests. While both microstructures exhibit comparable HDI stress magnitudes during initial tensile deformation, the equiaxed one demonstrates obviously enhanced HDI strain hardening compared to its lamellar counterpart as deformation progressed. Two factors are mainly responsible for the observed divergence in HDI stress evolution between the two microstructures. First and foremost is the surface-to-volume ratio of phase interface (sV), where the equiaxed structure shows significantly higher sV than its lamellar counterpart, which can offer more potential sites and better spatial interconnectivity of phase interfaces for GNDs development. The other factor is the microstructural size scale, in which the average layer thickness of the lamellar structure is considered being too small, as compared to the average grain diameter in the equiaxed one, to provide sufficient space for GND pileups to fully develop, which limits HDI strain hardening. This finding provides critical insights into microstructural design strategies for optimizing the development of HDI stress.

Hetero-deformation induced (HDI) stress and the effect of microstructural morphology on it were investigated in a near-alpha titanium alloy featuring lamellar and equiaxed initial microstructures. The development of HDI stresses were confirmed in the two types of microstructures under tensile tests. While both microstructures exhibit comparable HDI stress magnitudes during initial tensile deformation, the equiaxed one demonstrates obviously enhanced HDI strain hardening compared to its lamellar counterpart as deformation progressed. Two factors are mainly responsible for the observed divergence in HDI stress evolution between the two microstructures. First and foremost is the surface-to-volume ratio of phase interface (sV), where the equiaxed structure shows significantly higher sV than its lamellar counterpart, which can offer more potential sites and better spatial interconnectivity of phase interfaces for GNDs development. The other factor is the microstructural size scale, in which the average layer thickness of the lamellar structure is considered being too small, as compared to the average grain diameter in the equiaxed one, to provide sufficient space for GND pileups to fully develop, which limits HDI strain hardening. This finding provides critical insights into microstructural design strategies for optimizing the development of HDI stress.

Hetero-deformation induced (HDI) stress and the effect of microstructural morphology on it were investigated in a near-alpha titanium alloy featuring lamellar and equiaxed initial microstructures. The development of HDI stresses were confirmed in the two types of microstructures under tensile tests. While both microstructures exhibit comparable HDI stress magnitudes during initial tensile deformation, the equiaxed one demonstrates obviously enhanced HDI strain hardening compared to its lamellar counterpart as deformation progressed. Two factors are mainly responsible for the observed divergence in HDI stress evolution between the two microstructures. First and foremost is the surface-to-volume ratio of phase interface (sV), where the equiaxed structure shows significantly higher sV than its lamellar counterpart, which can offer more potential sites and better spatial interconnectivity of phase interfaces for GNDs development. The other factor is the microstructural size scale, in which the average layer thickness of the lamellar structure is considered being too small, as compared to the average grain diameter in the equiaxed one, to provide sufficient space for GND pileups to fully develop, which limits HDI strain hardening. This finding provides critical insights into microstructural design strategies for optimizing the development of HDI stress.