Preheating is the first but critical step for hot stamping high strength precipitate hardened aluminum alloys. To thoroughly understand the effects of preheating conditions—i.e., preheating rate and heating temperature—on the strength and hot deformation of aluminum alloys, a series of thermal–mechanical tests was performed to determine the post-hardness evolution and hot flow behaviors. Typical microstructures with different preheating conditions were also observed through transmission electron microscopy (TEM), with which a unified model of both hot flow and strength based on key microstructural variables was developed, enabling the successful prediction of macroscopic properties using different preheating strategies. The results have shown that for high strength AA7075 at the T6 condition, the dominant mechanism of precipitate evolution with increasing temperature is the coarsening of precipitates first, followed by dissolution when they exceed a critical temperature. A higher heating rate results in a slower coarsening and a relatively higher strength level. In addition, the flow stress of hot deformation is also higher using a quick heating rate, with more significant softening and reduced ductility.

Cold rolling is employed to improve mechanical properties of Mg–14Li–1Zn alloy. Microstructural evolution and mechanical properties are investigated. Results show that, as‐cast and as‐homogenized Mg–14Li–1Zn alloy is mainly composed of β phase with trace amount of tiny α phase particles. During tensile test, the discontinuous α phase leads to intergranular fracture, which is a main reason for the low strength and low elongation. After cold rolling, the distribution of α phase becomes much more dispersive. The tensile fractural morphology changes from brittle intergranular fracture to dimple fracture. The sheet with 70% thickness reduction possesses the ultimate tensile strength of 212 MPa, elongation of 9.4%, and microhardness of 60.12 HV. When the total rolling reduction is 90%, the tensile strength decreases slowly to 210 MPa, but the elongation increases sharply to 19.8%. Strengthening mechanisms of the Mg–14Li–1Zn alloy are attributed to strain hardening and grain refinement. Strain hardening plays an important role in the enhancement of strength. Grain refinement and the appropriate distribution of the α(Mg) can obviously improve the plasticity.

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In this study, Ag-Cu-Zn brazing alloy together with Cr or Ti powder had been used to braze diamond grits under different environments, such as: air, vacuum, argon gas protection, salt covering and carbon powder covering. The microstructure on the interfaces of diamond grits, brazing alloy and steel substrate was examined by Scanning Electron Microscopy (SEM) and optical microscopy. The results showed that by adding Cr powder, the diamond grits could be brazed onto the steel substrate in air and owned enough bonding strength and wear resistance when grinding granite. By adding Ti powder, the diamonds could be well brazed in vacuum or in the air with the protection of carbon powder. In brazing, the migration of Cr or Ti element to the surface of diamond and the forming of Cr or Ti rich area had significantly improved the wettability of the brazing alloy to the diamond grits. 140 Y.M. Zhou et al.

The as-cast Mg-14Li-1Zn alloy was hot rolled at different temperatures with the reduction of 50%, followed by cold rolling with the reduction of 80%. The effects of the hot rolling temperature on the microstructure and mechanical properties of the final specimens were investigated. The results show that the higher rolling temperature brings about a more homogeneous microstructure, which is favorable for the subsequent cold rolling. When the hot rolling temperature is 300°C, the final specimen possesses the highest tensile strength and hardness of 238 MPa and 67.7 HV, respectively. When the hot rolling temperature is 200°C, the final specimen possesses the highest elongation of 24.6%.