A new study by MIT engineers shows how shaving can damage blades. Human hair, 50 times softer than steel, can chip away a razor’s edge, the engineers found.
In the present study, the laser melting deposition (LMD) technology was adopted to fabricate FeCoCrNiMn and FeCoCrNiMnAl0.75 high entropy alloys (HEAs). Then, laser welding method was used to join the HEAs in forms of similar (FeCoCrNiMnAl/FeCoCrNiMnAl and FeCoCrNiMnAl0.75/FeCoCrNiMnAl0.75) and dissimilar (FeCoCrNiMnAl0/FeCoCrNiMnAl0.75) combinations, respectively. Ultra-depth field microscope and electron backscatter diffraction detection were used to observe the macro-morphology and microstructure, respectively. It was found that the width of the weld bead and heat-affected zone with higher aluminium content was larger. In both base metals and welded joints, aluminium promoted the face-centered cubic (FCC) phase transfer into body-centered cubic (BCC), significantly refined the grain and the dislocation density of HEA is also increased, which increased strength and hardness, and decreased ductility. Highlights The FeCoCrNiMn/FeCoCrNiMn, FeCoCrNiMn/FeCoCrNiMnAl0.75, FeCoCrNiMnAl0.75/F
Defects would occur in the weld joint of the wheel rims during the post-flash butt welding (FBW) process suffering from poor plasticity, which will deteriorate the quality and lifecycle of finish products. Therefore, the FBW process of the 440CL high-strength-low-alloy (HSLA) steel was physically simulated and the influence of flash parameters on FBW joints was systematically evaluated in this study. The results showed that the width of heat affected zone increased with accumulated flash allowance (δf) while declined with accelerated flash speed (vf). The recrystallization level would be intensified with increased δf. Meanwhile, the acceleration in vf populated the WZ with a more homogeneous microstructure, higher recrystallization degree and lower dislocation density. The hardness in WZ slightly reduced (202 → 195 HV) as increased δf but obviously dropped (192 → 177 HV) as increased vf. All tensile samples were fractured at the BM location and the tensile properties of FBW join
In this research, the ultra-thin Cu/Al metallic composite sheets of 0.06 ∼ 0.09 mm were successfully prepared by the self-designed four-high laboratory micro mill. The cold rolling reduction of single pass was up to 70%. The effect of different annealing temperatures on microstructure and element diffusion of the Cu/Al composite sheet interface was investigated at the microscale. The results show that with the increase of annealing temperature, the average grain size of Cu and Al increases gradually, the mutual diffusion of Cu/Al elements increases. Compared with the macroscale, the grain refinement of the ultra-thin Cu/Al composite sheets can promote the interdiffusion of Cu and Al elements. When the annealing temperature was 350 ∼ 450 °C, a relatively large number of micropores and microcracks appeared at the interface of Cu/Al composite sheet. When the annealing temperature was 350 °C, a diffusion layer was formed at the interface of the ultra-thin Cu/Al composite sheet, and t
To meet the increasing demand of multifunctional applications of microcomponents, metal composites have been gradually noted in micromanufacturing. In this paper, the formability of aluminium (Al)-copper (Cu) composite foils in micro deep drawing (MDD) was studied, and the mechanism involved was discussed. A two-layered Al-Cu composite with the thickness of 235 µm was selected and first rolled to 50 µm, and then annealed at 200, 300, 400 and 500 °C for 5 min prior to the MDD experiments. The results show that Al-Cu composite foil possesses the best combination of strength and ductility after annealing at 400 °C. With the increase in annealing temperature, the grains of both Al and Cu layers are refined, and in the meantime, the thickness of intermetallic layer also increases. The results from MDD tests indicate that the existence of intermetallic layer has a greater influence on the formability of the composite foil compared to the finer distribution of grains. On the basis of the