____________________ * Corresponding author: P. Bucci Street – 87036 Rende (CS) - Italy, l.filice@unical.it. FORMABILITY OF AZ31 MAGNESIUM ALLOY IN WARM INCREMENTAL FORMING PROCESS G. Ambrogio 1 , S. Bruschi 2 , A. Ghiotti 3 , L. Filice 1,* 1 DipMec University of Calabria, Rende (CS) – Italy 2 DIMS University of Trento, (TN) – Italy 3 DIMEG University of Padua, (PD) – Italy ABSTRACT: A number of scientists are currently involved in Incremental Forming investigation, in order to better understand the process and to extend its applicability to industrial practice. If flexibility is probably the main advantage deriving from Incremental Forming use, today a new point of view is given by the possibility to use the process instead of a sequence of operations, allowing also a better sustainability. Formability enhancing is one of the keyfactors of this success and for this reason it is widely investigated, also on lightweight materials, for which the use of a preliminary heating is required. In the paper the formability of Magnesium AZ31 is investigated in warm Incremental Forming, focusing the attention on the tools currently utilised for describing material formability. It is shown that Forming Limit Curves fail in this goal while a study of fracture, exploiting results of conventional tensile tests, supplies more appreciable results. KEYWORDS: AZ31, Formability, Incremental Forming 1 INTRODUCTION It is well known that Incremental Forming process allows a higher formability as compared to the traditional stamping processes due to the possibility to extend and control material forming “under necking conditions” [1-2]. This capability is surely more interesting when materials characterized by a low formability are processed. Among these, Magnesium is increasing its importance in the last years due to the need of lightweight materials in some applications and its high performance vs. weight ratio [3]. Reduction of pollution is just one of the reasons why the use of lightweight materials is today strongly encouraged. What is more, the possibility to obtain one component by a single process instead of a proper sequence, is today regarded as very interesting with the aim to reduce the environmental cost of the operations leading the processes more sustainable. However, Magnesium forming at room temperature is not possible, thus a new scenario is today given by the warm processes, in which an interesting level of formability is allowed thanks to material heating. Some preliminary tests in this way showed a suitable material behaviour [4-5]. The equipment to work Magnesium in warm conditions is not very expensive and thus interesting also from an industrial point of view. In the study here addressed, formability is approached deriving FLC conditions at fracture directly from uni- axial tensile tests in different cases in order to build modified FLDs in which necking occurrence is obviously overcome. Thus, the strain occurring in Incremental Forming is considered in order to investigate the process feasibility. This analysis tool may be used in two different ways: firstly as verifying technique, highlighting the points in which material breaking is possible, and giving an advise on the process robustness; secondly, as design technique, investigating the optimal process parameters (for instance temperature) that allow the higher formability, directly using cheap and fast tensile tests. All these aspects are introduced and discussed in the paper. 2 WARM SINGLE POINT INCREMENTAL FORMING ON MAGNESIUM ALLOY First of all, Warm Incremental Sheet Forming required a carefully attention to the equipment design in order to ensure a more homogeneous temperature distribution on the sheet. According to that, the equipment shown in Figure 1 was developed. It allows to clamp circular and square blanks by means of a proper blankholder. A backing plate was included into the device in order to