Evaluations of Microstructure in Ultra-Fine-Grained Matrix with Sintering-Assisted ECAP Process in Aluminum–Nickel Powders

Abstract

The aim of this study was the synthesis of intermetallic crystal dispersion in an ultra-fine-grained (UFG) aluminum matrix by the equal-channel angular pressing (ECAP) process, which provides severe plastic deformation (SPD) of aluminum-5 and 10% wt. nickel powders. The ECAP process of up to 20 passes was carried out at 200 °C. Intermetallic crystal particles in the UFG Al matrix were obtained in sintered samples at 500 °C for 1 and 5 h, interrupting the ECAP process. The scanning electron microscope (SEM) images were received for the microstructural evaluations. According to the SEM images, it was understood according to the quantitative observation and energy dispersive spectroscopy (EDS) analysis results that the Ni powders added to Al mostly remained in the block state in the matrix structure after the ECAP processes but started to dissolve in the matrix by increasing the ECAP pass number and sintering temperature. DSC and XRD analyses were carried out to investigate intermetallic crystal evaluation in the material. According to DSC analyses, the melting degrees of the alloys increase with the amount of Ni added. Melting enthalpies and melting degrees showed small changes in the number of ECAP passes. Also, electron backscatter diffraction (EBSD) images were obtained for the samples’ grain size and grain boundary angle measurements. It has been understood that the number of passes and the process temperature are effective parameters for the solid-state synthesis of Al3Ni intermetallic crystals in UFG by the ECAP process.