Effects of Squeezing Pressure and Hot Rolling on (Al3Zr/Al2O3 + ZrB2)/6016Al Nanocomposites Synthesized Under Electromagnetic Field

In situ 3-wt.% (Al3Zr/Al2O3 + ZrB2) particle-reinforced 6016Al-matrix composites were produced and squeezed at 650 degrees C. The effects of squeezing pressure (10-20 MPa) on the solidification microstructure and properties of the composites were investigated. Squeezed solidification of the 6016Al-matrix composites at 650 degrees C led to grain sizes of 65-70 mu m. The synthesized (Al3Zr/Al2O3 + ZrB2) particles were segregated along the grain boundaries. Fine Mg-Si-rich Guinier-Preston zones or precipitates (similar to 5 nm) were formed during solidification. Amorphous Al2O3 was observed adjacent to crystalline Al2O3 particles. The composites exhibited a lower yield strength (YS) of similar to 50 MPa because of the clustered porosity and agglomeration of reinforcement particles in hot spots (50-100 mu m), formed during solidification. The composite squeezed under 20 MPa exhibited a superior ultimate tensile strength (UTS) of 186 MPa as compared to 170 MPa of the composite squeezed under 10 MPa. Mechanical properties of both the composites were improved upon hot rolling. Upon 80% thickness reduction by hot rolling, the composite squeezed under 10 MPa exhibited increase of similar to 300% in YS, similar to 30% in UTS, and 100% in fracture strain, while the composite squeezed under 20 MPa exhibited increase of similar to 260% in YS, similar to 6% in UTS, and similar to 32% in fracture strain. The improvements in properties originated from improved strengthening efficiency of (Al3Zr/Al2O3 + ZrB2) particles and homogenization of the microstructure.