Formability and Spring-Back of Light Metals at High Strain Rates

Formability or plasticity of light metals, such as aluminum alloys and titanium alloys, are quite strain rate sensitive. For most normal plastic forming processes like forging, stamping, rolling and extrusion, their strain rates are usually at medium strain rates between 10–2 s−1 and 102 s−1, the formability becomes lower with increasing of strain rates. While at very low strain rates, the formability is often much higher, especially between 10–5 ~ 10–3 s−1, at which super-plasticity is found for many metals and alloys. Spring-back is quite normal for sheet and tube forming, it is very small when the strain rate is lower than 10–3 s−1, while it is usually very high when the strain rate is higher for medium strain rates (10–2 s−1 and 102 s−1), especially for titanium alloys. It has been found that there exists a range of strain rates around 1 × 103~5 × 103s−1 for many light metal alloys that the formability is increased remarkably, and the spring-back is also quite low. In this paper, variations of the formability and the spring-back with varied strain rates have been investigated, The research aims to find a suitable strain rate range with remarkable increased formability and lower spring-back, so that many sheet and tube parts of light metals can be formed with sufficient formability and very small spring-back at room temperature.