Microstructure and mechanical properties of Al-10Si alloy modified with Al-5Ti

The microstructure, fracture morphology and mechanical properties of Al-10 Si alloy modified with Al-5 Ti were analyzed and tested by optical microscopy, scanning electron microscopy, and universal electronic testing machine. Compared with unmodified Al-10 Si alloy, the area fraction of α-Al phase in Al-10 Si alloy modified at 740 °C increased first and then decreased with the increase of added amounts of Al-5 Ti, and reached the maximum when the added amount of Al-5 Ti was 0.5 wt.%. When the modification temperature increased from 700 to 740 °C with Al-5 Ti being fixed at 0.5 wt.%, α-Al dendrites were refined obviously and the area fraction remarkably increased. Compared with unmodified Al-10 Si alloy, the ultimate tensile strength and elongation of the alloy modified at 740 °C with 0.5 wt.% Al-5 Ti increased by 9% and 49%, respectively. The fracture surface of modified alloy predominantly exhibited ductile fracture.

Effects of annealing at 800 and 1000℃ on phase precipitates and hardness of Al_(7)Cr_(20)Fe_(x)Ni_(73)−x alloys

The effects of Fe content on the microstructure,phase constituents and microhardness of the as-cast,800℃or 1000℃-annealed Al_(7)Cr_(20)Fe_(x)Ni_(73)−x(x=13−66)alloys were investigated.Not all these alloys are composed of the single FCC phase.The BCC and B2 phases are found.It is confirmed that the BCC phase in the Al7Cr20Fe66Ni7 alloy is transformed from the FCC phase at about 900℃ during cooling.While in the 800℃-annealed Al7Cr20Fe60Ni13 alloy,the FCC phase is stable and the hardness decreases.After annealing at 1000℃,for the precipitation of the B2 particles,the Al content in the FCC phase decreases,which results in decreasing of the alloy hardness.Moreover,after annealing at 800℃,a small amount of Al-rich B2 particles precipitate at the phase boundary and some nanocrystal BCC phase precipitates in the FCC matrix,which increases the hardness of the Al_(7)Cr_(20)Fe_(x)Ni_(73)−x(x=41−49)alloys.These results will help to the composition design and processing design of the Al−Cr−Fe−Ni based high-entropy alloys.

Microstructure and mechanical properties of Al-Si alloy modified with Al-3P

Al-Si alloy was modified with Al-3P master alloy at 740℃.The effects of Si content(7,8,9,10 and 11 wt.%) and adding amount of alterant A1-3P(0,0.1,0.3,0.6,1.0 and 1.5 wt.%) on microstructures and tensile properties of the alloy were investigated with optical microscope(OP),Image Pro Plus 6.0,scanning electron microscope(SEM) and universal testing machine.When the content of Al-3P is 0.6 wt.%,the area fraction of primary a(Al) in the Al-Si alloy increases more compared to the unmodified alloy with an increase in Si content,which could be explained by the movement of non-equilibrium eutectic point.When the Si content is constant(Al-lOSi),with the increase of Al-3P content,the increased rate in area fraction of primary a(Al) phase in the Al-lOSi alloy increases first and then decreases.And when 0.6 wt.% Al-3P is added,the increase in area fraction of primary a(Al) phase is the largest.Compared to the unmodified Al-lOSi alloy,the tensile strength and elongation of Al-lOSi alloy increase by 2.3% and 47.0%,respectively,after being modified with 0.6 wt.% Al-3P alloy.The fracture mode of the modified Al-lOSi alloy is ductile fracture.