Yan Hongge

The effect of thermal exposure on the microstructure and hardness of as-cast Mg–Zn–Al alloys with Sn addition

Abstract Microstructural evolution and hardness changes of as-cast Mg-6Zn-2Al alloys with Sn addition during prolonged thermal exposure to 150 °C and 200 °C were studied using optical microscopy, X-ray diffraction, scanning electron microscopy and hardness tests. Neither obvious grain growth nor new phases were detected in these alloys during thermal exposure. There were initial precipitation hardening peaks followed by long-term hardness stability during thermal exposure to 150 °C, indicating that all the alloys exhibited excellent microstructural stability. There were two peaks in the hardness vs. annealing time curves of these alloys during thermal exposure to 200 °C, which corresponded to the precipitation of MgZn and Mg2Sn. The overall hardness of these alloys decreased with prolonged time, resulting from the aggregation and coarsening of Mg2Sn.

Application of a Novel Multilayer Spray Forming Technology in the Preparation of Large Dimension Aluminium Alloy Blanks

Principle of multilayer spray forming and preparation technique of tubes and billets by it were presented and described in the article. The marked characteristic of multilayer spray forming technology is the to-and-fro movement of spray system, so the preform is deposited layer by layer with the surface of the deposit retaining relatively low temperature during the spray forming process. The two outstanding advantages of multilayer spray forming are as follows: suitable for manufacturing large dimension blanks, higher solidification cooling rate. Now Al-Fe-V-Si alloy (8009) and SiC particle reinforced aluminium alloy metal matrix composite billets of 300–600 mm in diameter and tubular blanks of size up to 650 mm in outer diameter, 360 mm in inner diameter and 1 200 mm in length have been made with the technology. After extrusion, the material has good properties.