Effects of Annealing on Microstructure and Mechanical Properties of Backward Extruded Mg-0.5Mn-1Nd Alloy

Mg-0.5Mn-1Nd (wt.%) alloy has been prepared by zone purifying method followed by backward extrusion (BE) technique. The microstructures, recrystallization behavior from 150 to 400 °C and mechanical properties of Mg-0.5Mn-1Nd alloy were investigated. The alloy exhibited bimodal microstructures after BE deformation. The equiaxed grains changed to more homogeneous after annealing treatment in range of 150 to 250 °C. The similar trend was confirmed after thermal annealing treatment at different annealing temperatures. The abnormal grains growth was clearly observed when the temperature was higher than 350 °C. Compared with BE-Mg-0.5Mn-1Nd alloy, both yield strength and ultimate tensile strength were reduced after annealing treatment, whereas the elongation was increased correspondingly. These results were mostly related to the fine grain size and homogeneous secondary precipitate.

Synthesis and Evaluation of a Novel Retarded Acid Additive

A novel acidizing additive is developed to improve acidizing effectiveness, especially to solve the problems during acidizing process, like rapid acid-rock reaction rate etc. The monomer was synthetized by Mannich reaction. Experimental results indicate that the optimum conditions are: mass ratio 18.5:8:14 of formaldehyde to amine A and phosphorus B, reaction temperature 90°C, reaction time 14h, polymerization inhibitor hydroquinone dosage 0.25%, under which the degree of conversion amounts to 91%. Infrared spectrum shows the feasibility of synthesis scheme. Then the monomer copolymerized with AMPS under the conditions: mass ratio 24.2:4 of monomer to AMPS, reaction temperature 80°C, reaction time 1h, monomer concentration 40%, and initiator dosage 2.0%. The corrosion and secondary precipitate performance of the retarded acid system was investigated. The results indicate that this operating fluid has superior retarding effectiveness and excellent secondary precipitate behavior. By core displacement experiment, the excellent retarding property of the retarded acid was further confirmed.