An Experimental and Analytical Study of the Evolution of Crystallographic Texturing in FCC Materials

A Taylor type polcrystalline model, together with a new fully implicit time integration scheme have been developed to simulate the evolution of crystallographic texture during the deformation of face centered cubic metals deforming by crystallographic slip. The constitutive equations include a new equation for the evolution of slip system deformation resistance which leads to realistic macroscopic strain hardening behavior. The good predictive capabilities of theconstitutive equations and the time integration procedure are demonstrated by comparing numerical simulations against experimental texture measurements and stress-strain results in a series of homogeneous deformation experiments on OFHC copper.United States. Office of Naval Research (Grant ONR 0014-Sg-J-3040

Synthesis and Characterization of NanocrystallineMg-7.4%Al Powders Produced by Mechanical Alloying

Nanocrystalline Mg-7.4%Al powder was prepared by mechanical alloying using a high-energy mill. The evolution of the various phases and their microstructure, including size and morphology of the powder particles in the course of milling and during subsequent annealing, were investigated in detail. Room temperature milling leads to a rather heterogeneous microstructure consisting of two distinct regions: Al-free Mg cores and Mg-Al intermixed areas. As a result, the material is mechanically heterogeneous with the Mg cores displaying low hardness (40–50 HV) and the Mg-Al intermixed regions showing high hardness of about 170 HV. The Mg cores disappear and the microstructure becomes (also mechanically) homogeneous after subsequent cryo-milling. Rietveld structure refinement reveals that the crystallite size of the milled powders decreases with increasing the milling time reaching a minimum value of about 30 nm. This is corroborated by transmission electron microscopy confirming an average grain size of ~25 nm