Design and development of a dual-phase TRIP-TWIP alloy for enhanced mechanical properties

Triggering transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) mechanisms in metastable β titanium alloys (bcc, body centered cubic) have helped reaching unprecedented mechanical properties for Ti-alloys, including high ductility and work-hardening. Yet the yield strength of such alloys generally remains rather low. So far, mostly single-phase metastable bcc alloys have been developed. In this study, a dual phase TRIP/TWIP alloy is designed and investigated. While the β-matrix is expected to display TRIP/TWIP deformation mechanisms, the addition of a second phase, α in the present study, aims at increasing the yield strength. The composition was designed in the Ti-Cr-Sn system, based on Calphad prediction and on the semi-empirical d-electron alloy design approach. Results were compared to the published full β Ti – 8.5Cr – 1.5Sn (wt%) TRIP/TWIP alloy. The dual-phase alloy was prepared and processed to reach the desired microstructure containing about 20% α. It displays remarkable mechanical properties such as a ductility of 29%, an ultimate tensile strength of 1200 MPa and a yield strength of 760 MPa, 200MPa higher than the Reference single-phase β alloy. Analysis of the mechanical properties and deformation microstructures confirm the TRIP and TWIP effects, validating the proposed approach.

Effect of hot rolling on the corrosion behavior of AZ31 magnesium alloy

The aim of the present study is to investigate the effect of deformation conditions on the corrosion behavior of AZ31 (Mg-3Al-1Zn, % wt.) in 0.9% NaCl (wt.%) solution. The AZ31 alloy was hot rolled at 360 °C to 20 and 50% of thickness reduction. Electrochemical measurements were used to study the corrosion behavior of AZ31 alloy. Analysis of corrosion products after immersion test was performed using optical microscopy, X-ray diffraction and Raman spectroscopy. The mechanical properties of corroded samples were investigated using tensile test at room temperature. Results indicated that the corrosion rate was strongly affected by the hot rolling level. A lower corrosion potential and reduced polarization resistance was observed after hot rolling compared to the as received AZ31 alloy. The corrosion product was evidenced mainly as Mg(OH)2 compound exhibiting a filiform-like morphology. Apparently, the corrosion improved the room temperature ductility of AZ31 alloy.

Формирование упругопластических фронтов и откольное разрушение в сплаве АМг6 при ударных воздействиях

Full wave profiles were monitored by the laser interferometry method by means of a VISAR laser Doppler velocimeter under shock-wave loading of samples of AMg6 aluminum alloy. Analysis of these profiles was used to study the laws of elastic precursor formation and its amplitude variation during elastic–plastic transition front propagation in samples loaded by a shock wave of variable intensity. Critical stresses leading to the spall fracture of samples were determined as dependent on the strain rate under unloading.

Cu-Sn-Pb Alloy Fabricated by Powder Metallurgy and Its Application for Standard Curve Establishment of Portable X-Ray Fluorescence Instrument for Alloy Analysis on Bronze Relics

ABSTRACT One of the most important non-destructive methods for on-site analysis of bronze artifacts is portable X-ray fluorescence (XRF). However, bronze artifacts are usually heterogeneous in composition due to, among other things, the segregation of lead, which is hard to be eliminated through annealing treatments. In the present work, Cu-Sn-Pb alloys with homogenous composition and microstructure is fabricated by powder metallurgy technique. The suitability of the standard curve using Cu-Sn-Pb alloys by powder metallurgy as the standard samples for XRF on the analysis of bronze artifacts is evaluated. It is shown that this proposed method can be transferred to portable XRF to acquire accurate on-site composition information of bronze artifacts.