Forging of PM Ti–6Al–4V alloy at the temperature above β-transus and high strain rate: modeling and trials in industrial conditions

Abstract

The results of the forging process in open dies of the powder metallurgy (PM) Ti–6Al–4V alloy, carried out at the temperature above β-transus and at a high strain rate were presented. As an initial material for the research relatively cheap elemental powders were used. This approach gives a real chance for the implementation of the developed technologies. As the range of phase transition temperature in titanium alloys is influenced also by the technology of their production, the β-transus temperature was estimated for the PM Ti–6Al–4V alloy. Finite element method (FEM) numerical analysis of the forging process at the temperature of 1000 °C and high strain rate was performed. The results obtained by the FEM modeling were verified under industrial conditions. The forging trials were made at the temperature of 1000 °C on a screw press operating at a speed of 250 mm s−1. For comparison, the alloy was also studied in as-cast and hot-rolled conditions, which is widely used as a feedstock. The influence of the method of manufacturing feedstock on the microstructure and selected properties of the forgings was determined. This approach allowed for a qualitative assessment of the PM material. The forging process in open dies of two different feedstocks led to the production of forgings with a uniform and similar lamellar microstructure. Thus, it was shown that the heating conditions, the parameters of the forging process, and the method of cooling the product after forging have a decisive influence on the microstructure condition of the forgings shaped in the temperature range of the β phase.

Possibilities of Increasing the Durability of Dies Used in the Extrusion Process of Valve Forgings from Chrome-Nickel Steel by Using Alternative Materials from Hot-Work Tool Steels

“…So, in order to properly choose the tool material, we need to largely depend on the experience of the tool steel producers as well as the users of the tools, i.e., die forges [37,38]. At the same time, we should emphasize that, among the whole spectrum of available steels, there is none that would fulfill the expectations of the production in a complex way; so, while choosing the tool material [39], we can mostly base our decisions on the experience of the steel producers as well as the people directly connected with the production process [40]. The most common forging tool material used in forging processes are warm and hot operation tool steels, that is, 1.2343, 1.2344, 1.2367, 1.2999, etc., which are characterized by very good mechanical properties (high tensile strength and hardness, high abrasion resistance, high yield point of 2200 MPa).…”