No abstract

A two-step double-side friction stir welding (DS-FSW) technique was proposed to join 20 mm thick Mg-Y-Nd magnesium alloy plates. FSW was first carried out on one side of the butt joint, and then the plates were left-right reversed for the other side welding. The DS-FSW joint was free of defects and the weld nugget zone (NZ) showed fine equiaxial grains. An overlap zone with ultrafine grain ( ∼ 2.19 µm) and dispersive particles existed between the two welding tracks, beneficial to the integrity of the joint. The ultimate tensile strength (σ UTS ), yield strength (σ 0.2 ), and elongation rate (δ) of the joint were 277. 6, 204.1 MPa, and 7.27%. A high joint efficiency (σ UTS ratio between the joint and parent material) was achieved at ∼ 82.6%.

Effects of heat treatment on microstructures and tensile properties of IN718/TiC nanocomposite fabricated by selective laser melting

Laser based additive manufacturing technique has been found beneficial in fabricating complex components efficiently. In this paper, laser aided additive manufacturing with powder feeding (LAAM) was used to deposit SS410 or Inconel625 on SS416 substrate. Interfacial microstructure and mechanical properties of the deposited samples are investigated accordingly. Results indicated that deposit without obvious defects can be obtained. The interface samples exhibit comparative or slight lower tensile strength compared with the SS416 substrate. Fracture tends to occur at the SS416 side, either far from the fusion line for the SS410/SS416 sample or near the heat affected zone (HAZ) for the Inconel625/SS416 sample. Therefore, the LAAMed section are reliable enough. SS410 or Inconel625 both can be used for repair of SS416 parts.

The fabrication of nano-composites is quite challenging because uniform dispersion of nano-sized reinforcements in metallic substrate is difficult to achieve using powder metallurgy or liquid processing methods. In the present study, Al-based nano-composites reinforced with Al 2 O 3 particles have been successfully fabricated using friction stir processing. The effects of nano-Al 2 O 3 particle addition on grain structure evolution of friction stir processed Al matrix during post-weld annealing were investigated. It was revealed that the pinning effect of Al 2 O 3 particles retarded grain growth and completely prevented abnormal grain growth during post weld annealing at 470 °C. However, abnormal grain growth can still occur when the composite material was annealed at 530 °C. The mechanism involved in the grain structure evolution and the effect of nano-sized particle addition on the mechanical properties was discussed therein.