MICROSTRUCTURAL EVOLUTION OF Al-Cu-Mg SINTERED ALLOYS PROCESSED BY SEMI-SOLID EXTRUSION PROCESS

摘要

Grain size plays very important role in controlling the mechanical properties and performance of any engineering material during semi-solid extrusion process. Aluminum powder metallurgy (P/M) alloys are extensively used in automotive and aircraft industries because of their advantages like very light in weight and stronger than other metal alloys. Therefore, the aim of the present work is to study the Dynamic Recrystallized (DRX) grain size evolution of Al sintered alloys during semi-solid extrusion process. The working temperature range for semi-solid extrusion test was derived from TG/DTA analysis of sintered sample. Semi-sold extrusion tests were performed with a hydraulic press on sintered Al-4%Cu-0.5%Mg preforms with an Initial Preform density (IPD) of 90%, over different deformation temperatures (550 °C, 575 °C and 600 °C), different solid fractions (0.93, 0.76 and 0.56) and die approach angles of 30°, 45° and 60° respectively. All the extrusion tests were done with a low extrusion ratio of 1.44 and strain rate of 0.1 s~(-1) respectively. The DRXed grain size of Al-4%Cu-0.5%Mg preforms for different temperatures and die approach angles were evaluated by using an optical microscope and Scanning Electron Microscope. It was found that the mobility of grain boundaries were increased with increasing extrusion temperature, there by accelerating the growth of DRX grains. Higher deformation was observed at higher die approach angle irrespective of extrusion temperature.