Effect of pre-deformation on microstructure and mechanical properties of WE43 magnesium alloy II: Aging at 250 and 300℃

In this work,the microstructural evolution and mechanical properties of a pre-deformed WE43 magnesium alloy when aged at 250 and 300℃ were further investigated.It is found that the abundant deformation twins introduced by pre-deformation were maintained within the alloy during the aging treatment.Second particles formed at the twin boundaries and coarsened with aging time,especially at 300℃.When peak-aged at 250℃,the fine metastable β'''and β' precipitates formed in the un-deformed alloy have been transformed into relatively large β1 and β precipitates by the pre-deformation.While peak-aged at 300℃,the pre-deformation obviously refined the β precipitates.Mechanical properties indicate that pre-deformation can increase the yield strength by 19MPa and 54MPa for the peak-aged alloy at 250℃ and 300℃,respectively,and will not obviously deteriorate the tensile elongations.

Microstructure and kinetics of hot deformation WE43 magnesium alloy

The effect of compression on the microstructures and flow behavior of WE43 magnesium alloy was investigated in this article. The relationship between flow stress and strain rate was discussed. According to the empirical formula ε = Aδ^n exp （-Q/R T）, the value of heat activation of WE43 magnesium alloys is 297,15 kJ/mol. A mechanism of deformation softening of WE43 alloy in testing hot deformation was identified to be dynamic recrystallization.

Analysis of element loss, densification, and defects in laser-based powder-bed fusion of magnesium alloy WE43

It is well known that laser-based powder-bed fusion(L-PBF) additive manufacturing of magnesium(Mg) and its alloys is associated with high Mg loss due to vaporization(MgLoss) and high incidence of many types of defects in the manufactured parts/samples. Despite this,MgLoss, densification, and defect characteristics have not been holistically considered in the determination of the optimal values of L-PBF processing parameters for Mg and its alloys. This study presents a combined modeling and experimental approach applied for a widely used Mg alloy(WE43) to address this shortcoming in the literature. First, an experimentally calibrated model is proposed to determine MgLoss as a function of the L-PBF processing parameters. The model couples the temperature profile using a double ellipsoidal heat source with a Langmuir vaporization model and is calibrated using the width of the single-track L-PBF process and the measured Mglossusing inductively coupled plasma mass spectrometry(ICP-MS). Second, the densification of the samples is determined using a modification of the Archimedes method that considers the amount of MgLossin the calculation of the relative density. Third, a comprehensive and quantitative study is conducted on the relationships between the characteristics of porosity defects and the L-PBF processing parameters. Finally, the optimized L-PBF processing parameters are determined by considering the MgLoss, densification, and the characteristics of defects. The present study yields 0.23 wt.% MgLosscompared to 2 wt.% MgLossthat was reported in the previous studies. Furthermore, more than 99.5% densification is achieved while only ~2% and ~0.5% of the total defects are characterized as keyhole and lack of fusion defects, respectively.

Microstructures and mechanical properties of WE43 magnesium alloy prepared by friction stir processing

Mg-3.99Y-3.81Nd-0.53 Zr(WE43)casting alloy was subjected to single-pass friction stir processing(FSP)at a constant processing speed of 60 mm-min^(-1)and various rotation speeds of 400,800,1200,and 1500 r·min^(-1),and microstructures and mechanical properties of the experimental materials were investigated.FSP results in the generation of fine-grained microstructure,and fundamental breakage and dissolution of the coarse second phases.With the rotation speeds increasing,the average grain size of the FSP specimen in the stir zone first decreases and then increases,and the finest microstructure(~2μm)was prepared at the rotation speed of 800 r·min^(-1).Owing to the finer and more uniform microstructure,the mechanical properties of WE43 alloy after FSP are significantly improved.The variation tendency of the tensile properties is consistent with the change of the grain size.The maximum tensile strength,elongation,and average microhardness of the FSP WE43 alloy obtained at 800 r·min^(-1)are 290 MPa,17.2%,and HV92.9,respectively.The fracture morphology shows that small dimples can be observed on the FSP specimens,while the as-cast alloy fails through cleavage fracture.