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An Al–Cu–Mg–Zr alloy, which obtained different homogenization cooling rates by changing the heat-treated sample size, was compressed to various strains at the deformation temperature of 300 oC and strain rate of 0.01 s−1. The results showed that the homogenization cooling rate had strong effects on the hot deformation behavior of the alloy. The flow stress and relative dynamic softening rate of the alloy were significantly higher under a high cooling rate (HCR) than those under a low cooling rate (LCR). Furthermore, based on X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermodynamic equilibrium phase calculation, the substructure evolution in the grain interior, morphology, and spatial distribution of the precipitates were studied to determine the differences in the flow softening mechanism. The main softening mechanism could be summarized as dynamic recovery and precipitation coarsening for the LCR alloy and dynamic precipitation for the HCR alloy.

Multistage stress–strain curve correction based on an instantaneous friction factor was studied for axisymmetric uniaxial hot compression of 7150 aluminum alloy. Experimental friction factors were calculated based on continuous isothermal axisymmetric uniaxial compression tests at various deformation parameters. Then, an instantaneous friction factor equation was fitted by mathematic analysis. After verification by comparing single-pass flow stress correction with traditional average friction factor correction, the instantaneous friction factor equation was applied to correct multistage stress–strain curves. The corrected results were reasonable and validated by multistage relative softening calculations. This research provides a broad potential for implementing axisymmetric uniaxial compression in multistage physical simulations and friction optimization in finite element analysis.

Tool temperature has significant effects on tool wear and tool life in high-speed machining. Salomon hypothesized that increasing cutting speeds would make tool temperature rise to a maximum point and decrease after a certain cutting speed. However, the maximum tool temperature at a certain cutting speed in Salomon’s hypothesis has not been fully validated and widely accepted by academic researchers and industrial engineers. In this paper, a series of experiments for slot milling of Ti6Al4V alloy at different cutting speeds are carried out and tool insert temperatures are measured. The experimental results indicate that the slot milling tool temperature increases first and then decreases as the cutting speed grows. The critical cutting speed is 1500 m/min for slot milling of Ti6Al4V. To analyze the experimental results and find reasons for the decreased milling tool temperature at high cutting speed, we propose a tool temperature prediction model for slot milling insert. The effects of heat convection and heat conduction time on slot milling tool temperature are analyzed. The finite element method is applied to simulate the heat flux and tool-chip contact length under different uncut chip thicknesses. The simulated heat flux is included in the proposed tool temperature prediction model. The variation of tool temperature in the milling process is affected by heat generation, heat conduction time, and convection coefficient. This research demonstrates that the maximum tool temperature at a certain cutting speed in Salomon’s hypothesis can be accepted for interrupted machining processes.

The precipitation kinetics and its effect on hot working behavior of an Al–Zn–Mg–Cu alloy were studied under non-isothermal conditions and over a wide range of temperatures. The characterization techniques employed included in situ electrical resistivity measurements, differential scanning calorimetry, hardness testing and microstructure examination by scanning and transmission electron microscopy. The results showed that the precipitation kinetics during non-isothermal treatments were highly dependent on the thermal paths. Slow cooling processes led to coarse and sparse particle distribution. When heating to high temperatures, very fine precipitates with high density and homogeneous distribution were present at low temperature. Such fine precipitates showed unstable characters and dissolved quickly at higher temperature. Quantification of precipitate evolution during non-isothermal processing was obtained from in situ electrical resistivity measurements. The effects of heating paths on dynamic and static flow behaviors were also demonstrated to be significant. The degree of initial supersaturation controlled the nucleation rates and led to strong effect on dynamic and static precipitation, and on the flow stress softening.

High-speed repetitive continuous extrusion forming process (R-Conform process) was performed on the Al-Fe-Cu alloy. The microstructural evolution and mechanical properties were studied by x-ray diffraction, electron backscatter diffraction, transmission electron microscopy and tensile testing. The results show that a significant improvement of tensile ductility concurs with a considerable loss of tensile strength before four passes, after that the process on mechanical properties variation tends to be steady, indicating an accelerated mechanical softening occurs when comparing to low-speed R-Conform process. Microstructure characterization indicates that the accumulated strain promotes the transformation of low angle boundaries to high angle boundaries, thus leading to the acceleration of continuous dynamic recrystallization process, and the precipitates are broken, spheroidized and homogeneously distribute in Al matrix as increasing R-Conform passes. Massive microshear bands are observed after initial passes of R-Conform process, which may promote continuous dynamic recrystallization and further grain refinement during high-speed R-Conform process.

Ti-6Al-4V alloy is an attractive material in many industries due to its unique and excellent combination of strength to weight ratio and their resistance to corrosion. However, because of its low thermal conductivity and high chemical reactivity, Ti-6Al-4V alloy is generally classified as a difficult-to-cut material that can be characterized by low productivity and rapid tool wear rate even at conventional cutting speeds. It is well known that tool wear has a strong relationship with the cutting forces and a sound knowledge about correlation between cutting forces variation and tool wear propagation is vital to monitor and optimize the automatic manufacturing process. In the present study, high-speed end-milling of Ti-6Al-4V alloy with uncoated cemented tungsten carbide tools under dry cutting conditions is experimentally investigated. The main objective of this work is to analyze the tool wear and the cutting forces variation during high-speed end-milling Ti-6Al-4V alloy. The experimental results show that the major tool wear mechanisms in high-speed end-milling Ti-6Al-4V alloy with uncoated cemented tungsten carbide tools are adhesion and diffusion at the crater wear along with adhesion and abrasion at the flank wear. The cutting force component in the negative y-direction is more dominant of the three components and displays significantly higher magnitudes than that of the other two components in x- and z-directions. The variation of cutting force component Fy has a positive correlation with the tool wear propagation, which can be used as a tool wear indicator during automatic manufacturing process.