Investigation On Optimization Of Squeeze Casting And Heat Treatment Processing Of The Al-Cu Based Alloy

Squeeze casting is a kind of short route, high efficiency and precise forming technology,which combines the characteristics of casting and forging. It’s also a suitable method for thepreparation of high performance metallic materials. The cast Al-Cu based alloys are theheat-treatable aluminum alloys that can be prepared by squeeze casting for the high toughness.Based on our previous work, a composition optimized Al-(4.5~5.5) Cu-(0.3~0.6) Mn-(0.05-0.25) Ti-(0.05-0.15) RE-(0.05-0.20) Zr-(0.05-0.20) V (wt%) alloys with hightoughness was studied in this paper. The main concern focuses on two aspects. First, thesqueeze casting processing parameters of the alloy was optimized using orthogonal test andTaguchi method. And then, the influence of heat treatment processing on mechanicalproperties and microstructures of the alloy was investigated by single factor variable method.The results are as follows:1) The effect of several key squeeze casting parameters on microstructures andmechanical properties of the alloy was studied by using orthogomal method, opticalmicrosope, tensile and hardness test. The processing parameters for squeeze casting of thealloy were optimized. The results show that pressure is the most important factor followed bypouring temperature and mold preheating temperature and duration of applied pressure isrelatively nonsignificant when it is determined by mechanical properties and the area fractionof the second-phases of the alloy. The mechanical properties of the alloy are improved as thepressure increases. However, the improvement of the mechanical properties is reduced whenthe pressure is more than50MPa. The mechanical properties of the alloy increase at first andthen decrease as the pouring temperature increases. Both higher and lower die preheatingtemperatures are not benefit for the mechanical properties. The optimized squeeze castingprocessing parameters of the alloy are pouring temperature of730℃, die preheatingtemperature of200℃, applied pressure of75MPaand duration of applied pressure of30s. Thetypical values of ultimated tensile strength of218MPa, elongation of17.3%and Rockwellhardness of65.8of the squeeze cast alloy are obtained by using the optimized processing.2) The comparative study of the solution and aging heat treatment on mechanicalproperties and microstructures of the gravity cast and squeeze cast alloys was carried out by means of single factor variable analysis, OM, SEM, TEM, DSC and tensile and hardness test.The results show that the best heat treatment processing is the same for gravity cast andsqueeze cast alloys. The optimized parameters are solution treatment at540℃for10hours,and then quenched at room temperature water, artificial aging at175℃for8hours. Thetypical values of ultimated tensile strength of426MPa, elongation of16.9%and Brinellhardness of125of the squeeze cast alloy are obtained by using the optimized processing. Thesecond-phases in squeeze cast alloy is dissolved more completely than that in gravity castalloy. The squeeze cast alloy is more stable than the gravity cast alloy when they are overaged,which is attributed to the more refined α(Al) dendrite size, more dispersive precipitates in thesqueeze cast alloy in the same aging condition.