Design And Fabrication Of Graded Density Impactor

In order to simulate high-speed movement space debris on the ground, a graded density impactor is needed to be prepared which have a property of quasi-isentropic compression to the target, after impacting the projectile, whose speed can approach that of space debris. To get good performance of the quasi-isentropic compression, and then use it to achieve hypervelocity lauching of the projectile, the design and fabrication are the priority.In this paper, taking easy to sinter and obtain wide range desity into account, two kinds of "pillow" graded density impactors are designed and fabricated, which are W-Ti system(desingned density range:4.5～15.69g/cm3) and W-Mg system(desingned 1.74～15.0g/cm3),W and Ti are both hard to melt metal, thermophysical properties nearing, no brittle compound generated, desity distribution index P= 2. W and Ti are both refractory metal, their thermal physical properties similar to each other, no brittle compounds generated, easy to implement sintering; the density range of W and Mg are wide, nearly 10 times, W and Mg can not form brittle intermetallic compounds under normal conditions, but the W, Mg melting point varied widely, to achieve the same sintered is difficult.Prepared by powder metallurgy in this paper, mixing 8 different proportion mixture powder, through powder laminated method to achieve gradient distribution in accordance with design requirements, after cold isostatic pressing treatment and hot isostatic pressing, the materials can be wholely dense and get the best performance.The relative density of W-Ti impactor is nearly 99% by the way of drainage, XRD analysis showed that W andβ-Ti mainly exists in the form, no compound formation, metallurgical analysis shows small amount of a-Ti exist in pure Ti layer, from pure Ti layer to W-rich layer, the content of Ti decreased and the content of the white granular W increased, the second pahase compositon determination shows that composition distribution of the impactor comforms to its designed gradient distribution.SEM shows that W and Ti mechanical mixed, compact structure, no defects such as holes, each layer naturally transition, transition layer parallel, because of powder particle size difference, some agglomeration exists. EDS analyse shows that content chage of W and Ti follow its design and achieve a good gradient effect.In the same way prepared W-Mg graded density impactors, which are hard to sintered density at the same time, because of its big difference on thermophysical properties. XRD analysis indicated that no compounds generated between them, microscopic morphology observation shows that pure Mg layer sintered density while W-rich layer structure loose and exist some pore. Fracture morphology analyse shows that Mg as a complex matrix that will be wrapped W particles to sintered together, during the sintering, Mg play the role as bonding adhesive.