Preparation Of Al-Ti-C-Ce From Titanium Hydride And Its Refining Behavior

As one of the common metal materials in today's society,aluminum alloy is widely used in transportation,construction,aerospace,navigation,electric power,medical,decoration and other fields.With the steady development of various industries,the aluminum alloy has higher and stricter requirements for electrical conductivity,thermal conductivity,corrosion resistance,specific strength and toughness.There are many ways to improve the function of aluminum alloy.Refining the aluminum alloy grains can improve the strength and plasticity of the aluminum alloy,thereby improving the performance of the aluminum material.Incorporating the grain refiner into the aluminum alloy smelting,so that the aluminum melt obtains sufficient heterogeneous crystal nucleus during solidification,thereby refining the size of the metal grains to enhance the performance of the aluminum has become the most common in industrial production today.Economical and practical method.At present,the grain refiners with the highest usage rate in industrial aluminum alloy smelting are Al-Ti-B and Al-Ti-C.However,after adding Al-Ti-B to aluminum liquid,TiB2 particles are easily agglomerated and are easily Cr.The elements such as Zr and Mn are poisoned to make the refiner lose its effect.Since the Al-Ti-C refiner has been successfully prepared,it has made up for the defects of Al-Ti-B refiner in industrial production,and the application range of the refiner has been improved.However,in the preparation process,the Al-Ti-C refiner has a very poor wettability between the carbon source and the aluminum liquid,and the carbon source entering the aluminum liquid is difficult to combine with the Ti atoms in the aluminum liquid to generate sufficient TiC particles.Therefore,Al-Ti-C refiner is also greatly limited in industrial production.In this paper,the rare earth element lanthanum is introduced into the Al-Ti-C preparation process to improve the wettability of the carbon source and the aluminum liquid,thereby increasing the formation rate of the TiC particles.In the industrial preparation process of Al-Ti-C refiner,titanium source is usually used to introduce Ti source.The melting temperature is generally between 1200°C and 1300°C.The high temperature will not only cause fluorine dust pollution,but also cause oxidation of the alloy.Burning is serious.In the preparation of Al-Ti-C refiner,titanium hydride is used instead of titanium fluorophosphate.The maximum temperature during the preparation process does not exceed 950°C,which avoids the burning of the alloy caused by high temperature and eliminates the environmental pollution caused by fluorine dust.Al-Ti-C-Ce grain refiner with Al-3Ti-0.2C-3Ce and Al-3Ti-0.2C-6Ce ratio was prepared,and the Al-3Ti-0.2C refiner was prepared.The two-phase morphology,phase composition and phase distribution were compared and analyzed to investigate the effect of the amount of Ce added on the formation of the second phase in the refiner during the preparation of Al-Ti-C-Ce and the Ce element in the fine The movement in the agent.The experimentally prepared Al-3Ti-0.2C master alloy is composed of three phases of Al,TiAl₃ and TiC.The Al-3Ti-0.2C master alloy has a large number of second phases of needle-like,thin strips and blocks,which are mainly distributed in the grain boundary and the crystal.And a small amount of flocculent second phase is dispersed in the matrix.From the results of the line scan,it was found that Ti and C had no abnormal concentration and segregation along the grain boundaries and grain boundaries in the crystal,and they were uniformly distributed throughout the crystal boundaries and crystals.TiH₂ and graphite are used as Ti source and C source in the preparation of Al-3Ti-0.2C master alloy.TiH₂ is heated by the aluminum liquid to liberate Ti atoms,and Ti atoms are combined with graphite in the melt to form TiC particles,which are combined with Al atoms to form TiAl₃.The grain size of pure aluminum decreases with the addition of refiner.When the amount of refiner is 0.01%-0.05%,the grain size of the sample increases with the addition of refiner,and the refining effect is most obvious.When the amount of the refiner added reaches 0.05%,the refining effect of the refiner is saturated,and then the curve becomes smooth,and the change in the grain size and the addition amount of the refiner is not obvious.The optimum refining amount of Al-3Ti-0.2C master alloy refiner is 0.05%.The prepared Al-3Ti-0.2C-6Ce master alloy is composed of??Al?,?TiC?,?TiAl₃?,(Ti₂Al₂₀Ce)phases.The grain boundary of Al-3Ti-0.2C-6Ce casting is a continuous eutectic structure,and a large number of coarse second phase structures are distributed in the crystal.The grain boundary eutectic and the second phase in the crystal contain Ti₂Al₂₀Ce phase.The second phase structure of some large particles is a composite structure grain,and the peritectic structure of TiC and Ti₂Al₂₀Ce with dark color is present inside the second phase particles.TiC particles are mainly distributed in the crystal,and a small amount is distributed in the boundary and exists in the form of clusters.The addition of Ce element improves the wettability of graphite and aluminum liquid and promotes the formation of TiC particles.In the second phase particles of Al-3Ti-0.2C-6Ce master alloy,the distribution of element C is relatively uniform,the distribution of C and Al inside the particles is relatively low,and the distribution of Ti and Ce is relatively high,especially the distribution of Ce is significantly high.In the outer region of the particle;in the black region inside the second phase,the C content is extremely high,and the Ti and Ce contents are low.In the refinement experiment,the grain size of pure aluminum decreases with the addition of the refiner.When the refiner is added in the range of 0.01%-0.03%,the grain size of the sample increases with the addition of the refiner,and the refining effect Most obvious,when the amount of refiner added reaches 0.03%,the refiner refining internal effective nucleation core has reached saturation,then the curve becomes smoother,and the change of grain size and refiner addition amount is not obvious.Ce atom can reduce the surface free energy of Ti₃Al phase and greatly prolong the refinement reaction time.During the solidification of Al-3Ti-0.2C-6Ce master alloy,the second phase in the crystal is formed by the peritectic reaction of Ti,Ce and Al on the surface of TiC clusters.The second phase of grain boundary is Ti,Ce and TiC.When a impurity atom is displaced to the grain boundary,a peritectic reaction occurs.The addition of Ce can solve the problem of wetting of graphite and aluminum melt,and increase the content of TiC particles.TiC particles act as the core of nucleation in aluminum melt,increasing the number of nucleation.Ce element can not only promote TiC particles.It can also improve the anti-aging property of the refiner.The reason why the refining ability of the Al-Ti-C-Ce master alloy is higher than that of the Al-Ti-C master alloy is not only because the addition of Ce atoms increases the content of TiC particles.Moreover,during the refinement process,Ce atoms are enriched at the grain boundary of the aluminum alloy to inhibit the growth of the aluminum alloy grains.