drawing force was as high as 50–70%. However, this effect weakens to the vanishing point with increasing the operation time of the die. An analysis of the chemical composition of the die and periodic examination of the surface with an electron microscope showed that, for any drawing conditions and material, there is mass transfer of chemical elements from the workpiece to the die surface. Under heavy drawing conditions with an uncoated die, mass transfer occurs in the first centimeters of drawing even if a lubricant is used. When there is a film on the die, the elapsed time (the number of meters drawn) until mass transfer to the working surface becomes evident increases by several orders of magnitude. Selective contamination of the film by the chemical elements from the workpiece is still observed, but the film continues operating until completely fretted. Tests and study showed that for almost any working tool material and any work alloy, a film with optimal efficiency and wear resistance could be created. The practicality the wearlessness principle due to periodic renewal of the film is enormous. It has been noted that the higher the strength, hardness, and wear resistance of the tool material, the higher the efficiency of the periodically renewed coating. Fig.5: An item manufactured by explosive stamping from a low-ductility titanium-base alloy coated with a plasticizing film Another revealing example of the efficiency of softening films was a comparative explosive stamping test on titanium-base alloys. Sheet pieces were tested for manufacturing ring stampings with an overall strain of 12% at a strain rate of 7500 m s-1. Previously, a high-ductile titanium-base alloy (1.5Al-1.0Mn; σ = 600 MPa, δ = 20%) was used to manufacture these stampings. There were no problems in one-stage stamping of this alloy. The titanium-base alloy (6.0Al-2.0Zr-1.0Mn-1.0V), which has higher strength but lower ductility (σ = 1000 MPa, δ = 6%), is evidently preferable in terms of performance. However, with this substitution, cracking and warping were observed during stamping, even under incremental loading. The application of a softening oxide film to the original titanium sheet resulted in a defect-free stamping, which is shown in Fig. 5. References 1. Miatiev, A.A. (2000) NEW ADVANCES IN SURFACE PHYSICS, CHEMISTRY, AND MECHANICS: MATERIALS WITH DEPOSITED OXIDE FILMS, Findings, Effects, and Applications. Izd. Mosk. Gos. Univ. Pechati, Moscow.
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