Effect Of Nano-Ti Particles On The Microstructure And Properties Of AZ91 Alloy And Pure Magnesium

Ti+AZ91 alloy(Ti particle reinforced AZ91 alloy)was prepared by mechanical stirring and mechanical + ultrasonic stirring,and the influence of 0.02wt% Ti on the structure and mechanical properties of AZ91 alloy was studied;Ti/Mg composite material with Ti particles of different sizes(50nm,100 nm,300nm)were prepared by high-speed shear mixing device,to explore the effect of different sizes of Ti particles on the yield(the ratio of actual and theoretical additions)and the agglomeration effect,as well as the effect of 0.037 wt%,0.41 wt%,0.70 wt% Ti particles on the microstructure and mechanical properties of as-cast and extruded pure Mg.The main findings are as follows:(1)The high-speed shear mixing device could eliminate the agglomeration of nano-titanium particles in the alloy melting process.Ti+AZ91 alloy were prepared by,mechanical stirring and mechanical + ultrasonic composite stirring.When the theoretical addition amount of Ti(50nm in size)particles varies from 0.15 wt% to 1.5wt%,the actual addition amount is only 0.02-0.03 wt%.During the preparation of Ti/Mg composite alloy,increase of the size of nano-titanium particles leaded to the raised yield of Ti.Increacent size of Ti particles of 50 nm,100nm,and 300 nm resulted in the elevated yield of titanium,which were 24.67%,27.33%,and 46.67%respectively.(2)During the preparation of Ti+AZ91 alloy,Ti element induced the appearance of(?+?)phase layered eutectic structure in AZ91 alloy.Ti distributed in the transition region between ?-Mg phase and ? phase.Meanwhile,with Ti addition,the volume fraction of the ? phase increased and the microstructure refined.(3)The addition of Ti element can effectively improve the yield strength of AZ91 alloy,but it weakens the plasticity and the tensile strength of the alloy.The yield strength of Ti+AZ91 alloy increased 32.26%,and the elongation and tensile strength decreased 69.97% and 11.36%,respectively.(4)During the preparation of Ti/Mg composites,there is no new compound phase of Ti and Mg.Ti element is dispersed and distributed in the pure magnesium matrix in form of Ti element.The agglomeration effect of nano-Ti particles is influenced by sizes.when the original size is 50 nm and 100 nm,the reinforcing phase of titanium particles after agglomeration is relatively small,but the size of the reinforcing phase of titanium particles after agglomeration of 300 nm Ti particles is slightly larger.After the extrusion process,the reinforcement phase of the titanium particles becomes more dispersed and fine.(5)The titanium particle reinforcement phase can refine grains of as-cast and extruded pure Mg.The grain sizes of as-cast Ti/Mg composites with titanium particle reinforcement phase content of 0wt%,0.037 wt%,0.41 wt%,and 0.7 wt% are 2.15 mm,1.98 mm,1.11 mm,1.15 mm,respectively,and the grain sizes of extrued Ti/Mg composites are 64.3?m,61.8?m,27.4?m,and 29.7?m.(6)The reinforcing phase of titanium particles can significantly improve the strength of the as-cast and extruded Ti/Mg composites,but it will reduce its elongation.the yield strength of as-cast Ti/Mg composites with titanium particle reinforcement phase content of 0.037 wt%,0.41 wt%,0.7 wt% increased-2.91%?11.17%?18.45%,and the tensile strength increased 4.29%?21.43%? 20.00% respectively,while the elongation decreased 7.69%?10.78%?27.69%,respectively.The yield strength of extruded Ti/Mg composites with titanium particle reinforcement phase content of0.037 wt%,0.41 wt%,0.7 wt% increased 4.84%?25.81%?29.03%,the tensile strength increased 4.81%?29.41%?14.97%,The extruded elongation of Ti/Mg composites with Ti particle reinforcement phase content of 0.037 wt% and 0.41 wt% increased by 1.85%and 8.33%,respectively.Ti/Mg composites with Ti particle reinforcement phase content of 0.7 wt% were extruded.The compressive elongation decreased by 16.67%.