Abstract:A novel dynamically controlled plasma arc welding process was introduced, which is able to minimize heat input into the workpiece materials while maintaining desired full penetration, and it was used to weld Ti-6Al-4V alloy sheets. The microstructures, facture surfaces and microhardness of the welded joints were characterized by using optical microscope, scanning electron microscope (SEM) and Vickers microhardness tester. Comparing with welds such as gas tungsten arc and conventional plasma arc processes, the experimental results revealed the improvements when using the present process including: 1) reducing prior-beta (β) grain size and prohibiting formation of hard martensite phases in the fusion zone due to the decreased heat input; and 2) better toughness and higher hardness.

Key words: dynamically controlled plasma arc welding; Ti alloy welding; microstructure; fracture; microhardness