Search

In order to better understand the effect of the temperature and load on recrystallization behavior of DD5 single-crystal hollow blade tenon, samples with different loads were heat treated at different solution temperatures in a furnace. Optical microscope and scanning electron microscope were used to study the microstructure of recrystallization and size distribution of γ′ phase after solution treatment. Results show that there are no new grains found after solution treatment at 1230 °C/4 h, air cooling. However, the depth of load affected area increases with the bearing load and the size and depth of recrystallized cellular structure with newly-formed γ′ phase particles increase with the load below the solution temperature. Besides, the recrystallized nuclei begin from the dendrite when the solution treatment is 1315 °C/4 h, air cooling. The dendrite arms are passivated and the boundary between dendrite arm and interdendritic space disappear and γ/γ′ phase eutectic structure exists between dendrites in the recrystallization area. Moreover, the recrystallization area and the primary dendritic size gradually increase with the increase in load above the solution temperature.

The preparation of metal particle reinforced aluminum matrix composites by powder metallurgy has been widely studied in recent years. In this work, the effect of microwave sintering temperature on the microstructure and mechanical behavior of high-entropy alloys (HEAs) reinforced aluminum matrix composites prepared by powder metallurgy was investigated. Due to the outstanding microwave absorbing property of ferromagnetic HEAs particles, the composites sintering proceeded efficiently. At 480 °C, the aluminum matrix in the composite material is more compact, and the HEAs particles in the composite material are more evenly distributed, and the interface between HEAs particles and aluminum matrix is smooth. At 500 °C, the intensity of HEAs diffraction peak in the composite material changes significantly. At 520 °C, AlNi solid solution phase with BCC structure appears in the HEAs region, and the HEAs structure changes from FCC to FCC + BCC, and Al5Cr8, Al5Co2 and Al2Cu phases precipitate. At 480 °C, the nanohardness and elastic modulus at the interface reaches 1245.31 MPa and 72.45 GPa, respectively, showing relatively excellent interfacial bonding strength. The elastic modulus of both HEAs reinforcement and aluminum matrix decrease at a sintering temperature above 480 °C, and the composites have hard and brittle characteristics. At 480 °C, the macroscopic compression and yield strengths of composites are ~ 421.2 MPa and ~ 289.5 MPa, and the maximum shrinkage rate is ~65.3%, exhibiting excellent strength and toughness.

In situ 5wt%Al3Zr/6063Al composites were fabricate by a direct melt reaction method (DMR) and then processed by deformation pretreatment. Process of the pretreatment was forging of 70% deformation at 450 °C and friction stir processing (FSP). The high strain rate superplasticity of the composites was studied by modern analytic determination methods. The results show that the average grain size of the composites is less than 10 μm after forging and FSP. The composites exhibit superplasticity at the temperature from 350 to 500 °C and initial strain rate from 1.0×10−3 s−1 to 1.0×10−1 s−1. The elongation reaches 330% and the sensitive index (m value) is 0.45 at the initial strain rate of 1.0×10−2 s−1 and the temperature of 500 °C. The dominant mechanisms of superplastic deformation are grain boundary sliding and dislocation slip which is synergized with moderate grain growth and dynamic continuous recrystallization

The TiB 2 /7055Al Nano-composites were fabricated under the ultrasonic and magnetic coupled field. The results show that TiB 2 particles in the coupled field have a small size, with 80∼100 nm, a ball shape, a uniform distribution and a reaction to generate TiB 2 particles with high efficiency. When the ultrasonic power is 0.8 kW and exciting current of magnetic field is 200 A, frequency is 5 Hz, approximately 82.4% of TiB 2 reinforcement particles sizes are in range of 0.2∼0.5 μm, the number of particles whose sizes are in the range of 0.8∼1.2 μm reduce to about 1.6%, therefore, the thinning effect is nearly twice as much as generated in a single ultrasonic field of 0.8 kW.

Malicious processes usually cooperate with concealing technology to hide themselves. The detection against hidden processes can effectively narrow the range of malicious processes. Behavior analysis is then implemented on the filtered process to finally locate the malicious one. In this paper, a method of hidden process detection and behavior forensics based on memory analysis is proposed. It uses virtual machine monitor to extract and analyze memory data, detecting hidden processes; then analyzes the executable code of the target process to determine whether there is malicious behavior during the operation of the process. Experimental results demonstrated the effectiveness and the acceptable performance overhead of the proposed method.