论文部分内容阅读
由于从循环利用的废料中不断累积增加Fe元素等杂质元素,所以铸造铝合金零部件高性能的要求往往很难实现。要求合金中粗大板条状的含铁化合物β-Al5FeSi在不使用变质剂和昂贵的纯铝锭条件下转变成无害的形貌结构。在凝固过程中通过利用超声振动来检测分析其对具有不同铁含量的Al-7%Si合金坯料的显微组织的变质效果。在感应加热至半固态温度583℃后,立即对超声熔体处理的坯料进行触变铸造,然后对触变铸造的铸件进行微观组织和拉伸性能检测分析。在触变铸造时,要求球形的初生α-Al相充填合金组织中的微小孔洞中,以便首先确定在坯料中通过超声熔体处理使合金显微组织产生变质效果。在605~630℃温度范围内进行超声熔体处理时,初生α-Al相从树枝状晶转变为细小的圆球形形貌。与未进行超声熔体处理的坯料相比,坯料超声熔体处理后合金中的粗大板条状β-Al5FeSi化合物相变得明显细小。升至583℃后进行半固态铸造不会明显改变β-Al5FeSi化合物的尺寸大小,可是却会使初生α-Al相的形貌变得更圆整,这有利于触变铸造。经预先加热的坯料进行触变铸造后,由于低的铸造温度,产生了快速凝固效果,使得合金中的共晶硅层片变得特别细小。在对超声熔体处理的坯料进行触变铸造时,具有不同铁含量的触变试样的抗拉强度变化并不大,即使合金含铁量达到2%。然而,用未处理的Al-7%Si-2%Fe合金坯料进行触变铸造时,其强度较差,仅为80 MPa,而用超声熔体处理的同种合金坯料,其抗拉强度达180 MPa。用超声熔体处理的不同含铁量的Al-7%Si合金坯料进行触变铸造时,其伸长率也提高了约一倍,例如触变铸造超声熔体处理的Al-7%Si-0.5%Fe合金坯料时,试样的伸长率为11%,而未进行超声熔体处理的同种合金触变铸造试件,其伸长率只有5%。
Due to the continuous increase of waste elements such as Fe elements and other impurities from the recycling of waste, so the casting of aluminum alloy parts of the high performance requirements are often very difficult to achieve. It is required that the coarse lath-shaped iron-containing compound β-Al5FeSi in the alloy be transformed into a harmless topography without the use of a modifier and an expensive pure aluminum ingot. The effect of metamorphism on the microstructure of Al-7% Si alloy billets having different iron contents was examined by using ultrasonic vibration during solidification. After induction heating to a semi-solid temperature of 583 ° C, the melt-treated billet was subjected to thixotropic casting immediately, and then the microstructure and tensile properties of the thixocasting castings were examined and analyzed. In thixotropic casting, it is required that the spherical primary α-Al phase be filled into minute holes in the alloy structure so as to first confirm that the microstructure of the alloy is deteriorated by the ultrasonic melt treatment in the billet. In the temperature range of 605 ~ 630 ℃ during the ultrasonic melt treatment, the primary α-Al phase transition from dendritic to a fine spherical morphology. Compared with the blank without ultrasonic melt treatment, the coarse lamellar β-Al5FeSi compound in the alloy after ultrasonic melt treatment of the billet became obviously finer. Casting to 583 ° C and subsequent semi-solid casting does not significantly change the size of the β-Al5FeSi compound, but rather the morphology of the primary α-Al phase becomes more rounded, which is good for thixotropic casting. After preheating the billet for thixotropic casting, a rapid solidification effect occurs due to the low casting temperature, so that the eutectic silicon layer in the alloy becomes extremely small. The thixotropic samples with different iron contents did not change much in tensile strength when the ultrasonic melt-processed billets were thixotropically cast, even though the iron content of the alloy reached 2%. However, when untreated with an untreated Al-7% Si-2% Fe alloy billet was thixotropic cast, its strength was poor at only 80 MPa, whereas the same alloy billet treated with ultrasonic melt had a tensile strength of 180 MPa. Al-7% Si alloy billets with different iron contents treated with ultrasonic melt also have about a doubling of their elongation when subjected to thixotropic casting, such as thixotropic cast ultrasonic melt-treated Al-7% Si- 0.5% Fe alloy billets, the elongation of the sample is 11%, while the same alloy thixotropically cast test piece without ultrasonic melt treatment, the elongation rate of only 5%.