Distribution of Mechanical Properties by Volume in Titanium Billets Processed by Twist Extrusion

Abstract

The influence of multipass processing by Twist Extrusion (TE) on distribution of mechanical properties by volume in commercially pure (CP) titanium billets is investigated. Experiments show that the mechanical properties are almost homogeneous in the billet cross-section already after the second pass of TE. This can be explained by mixing effect and saturation of properties as well. Warm TE leads to the formation of high strength properties in combination with high plasticity. Ultimate and yield stresses of the billet processed by two cycles of TE increased, in comparison with initial state, by 30% and 60% respectively. The value of the reduction in area remained at the initial value. This fact is indicating a high technological plasticity of the material, i.e. its ability for further shaping by metal forming methods.

Twist Extrusion as a Potent Tool for Obtaining Advanced Engineering Materials: A Review

“…This refers particularly to aluminum and Al alloys, [41][42][43]49,52,72,118,119] copper and Cu alloys, [25,34,36,39,45,63,65,68,[120][121][122][123] titanium and its alloys, [64,65,70,[124][125][126][127][128][129] as well as various steels. This refers particularly to aluminum and Al alloys, [41][42][43]49,52,72,118,119] copper and Cu alloys, [25,34,36,39,45,63,65,68,[120][121][122][123] titanium and its alloys, [...…”

“…[36,41,91,123,124] In Sections 2 and 3.1, the cyclic character of deformation under TE was considered and two possible routes were discussed: multipass TE with dies with the same sign of shear in their two shear zones (route I) and those with opposite sign of shear (route II). This can be attributed to a reduced tendency to grain fragmentation with increasing strain.…”

“…To date, the effect of TE on microstructure and the mechanical performance has been investigated for a number of metals and alloys. This refers particularly to aluminum and Al alloys, [41][42][43]49,52,72,118,119] copper and Cu alloys, [25,34,36,39,45,63,65,68,[120][121][122][123] titanium and its alloys, [64,65,70,[124][125][126][127][128][129] as well as various steels. [61,62,73] There are some limitations on the applicability of TE processing to high strength materials.…”

“…Saturation of strength with increasing strain, even for a not fully uniform strain distribution, leads to practically uniform strength in billets TE-processed through such dies. [36,41,91,123,124] In Sections 2 and 3.1, the cyclic character of deformation under TE was considered and two possible routes were discussed: multipass TE with dies with the same sign of shear in their two shear zones (route I) and those with opposite sign of shear (route II). As shown in ref., [43,91] route II gives rise to more effective fragmentation, which is also in agreement with the theoretical predictions and experimental evidence.…”

The Occurrence of Ideal Plastic State in CP Titanium Processed by Twist Extrusion

“…[14,31] On the basis of the observations above, as well as the fact that the equivalent strain in the center of the billet cross-section after one pass is %0.5 (see Figure 4), one can assume that the mechanical properties in the axial area will reach those in the corners of billet after 8 passes, that is, once the central region accumulates a strain of e s % 4. The σ YS reaches the values of %640 MPa in these areas.…”