Effects of Sc and Zr Addition on Microstructure and Mechanical Properties of AA5182

The effects of 0.1 wt.% Sc and 0.1 wt.% Zr addition in AA5182 on microstructure and mechanical properties were investigated. Results show that Al3(ScxZr1−x) dispersoids formed in AA5182. Observation of ingots microstructures showed that the grain size of 5182-Sc-Zr alloy was 56% lower than that of based AA5182. Isothermal annealing between 230 °C and 500 °C for 2 h was performed to study the recrystallization, tensile properties and dispersoid coarsening. The recrystallization was inhibited by the dispersoids, and the alloy microstructure remained deformed after annealing. Al3(ScxZr1−x) in AA5182 was stable when annealing below 400 °C, while parts of dispersoids coarsened significantly when heating at 500 °C. The addition of Sc and Zr allowed YS of 5182 alloy to achieve 247.8 MPa, which is 100 MPa higher than the corresponding AA5182. The contributions of Orowan strengthening and grain boundary strengthening were obtained by calculation.

Study of Micro-Upsetting by Finite Element Simulation Based on Crystal Plasticity and Grain Boundary Strengthening Theories

The properties of individual grains affect the mechanical behaviors and response of materials in micro-scaled deformation, viz., microforming, and there are unknown phenomena and deformation behaviors existing and limiting the wide application of microforming due to size effect. In this paper, a composite model combining crystal plasticity and grain boundary strengthening theories was developed for numerical investigation into the effect of grain boundaries on the plastic deformation of copper micro-upsetting. By comparing the results with and without grain-boundary structure, it is revealed that grain boundaries, which act as the barriers of crystal slip, result in the enhanced flow stress and the discontinuous distribution of stress and strain. The grain size effect is also considered in this research, and the results show the coarse-grained material reduces the flow stress and enhances the inhomogeneous deformation.

Mechanism of Gradient Strengthening Layer Formation Based on Microstructure and Microhardness of Inconel 718 Grinding Surface

Gradient strengthening layer will emerge on the grinding surface of Inconel 718 due to the difference of microstructure. The surface microstructure and microhardness are not independent of each other, and the microhardness is the embodiment of the microstructure evolution in the strength aspect. In this paper, the microstructure observation, microhardness experiments and strengthening theory were combined to analyze. The experimental results show that the grinding surface consists of grain refinement layer and high-density dislocation layer. The grain refinement layer is constituted of equiaxed nano-grains and elongated grains, in which grain boundary strengthening occurred leading to an increase in microhardness. Dislocation strengthening occurred in the high-density dislocation layer, in which the increment of dislocation density is approximately 3.54 × 109 mm− 2 compared with inner matrix. Microhardness of high-density dislocation region reaches the maximum (438.6 ± 11.1 HV0.01) because of the dislocation strengthening. The variation of microhardness is discussed from two strengthening mechanisms of grain boundary strengthening and dislocation strengthening, and the strengthening mechanism in the different regions of grinding surface is revealed. The calculated microhardness increments through these mechanisms in the refined-grain region and the high-density dislocation region are basically consistent with the measured values.