A new method of characterizing equivalent strain for equal channel angular processing

Abstract

In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing (ECAP), a new approach to characterize the equivalent strain was proposed. The results show that there exists better accordance between mechanical property (such as hardness or strength) and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as: ɛ=k₀exp[−(k₁M−k₂)²], where M is the strength or hardness of the material, k₁ is the modified coefficient (k₁∈(0, 1)), k₀ and k₂ are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material, respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter relating to material property rather than the classical geometry equation.

Keywords

equal channel angular processing (ECAP) / equivalent strain / mechanical property / characterizing method

References

[1] SegalV. M.. Materials processing by simple shear [J]. Materials Science and Engineering A, 1995, A197: 157-164

[2] IwahashiY., WangJ. T., HoritaZ., NemotoM., TerenceG. L.. Principle of equal channel angular pressing for the processing of ultra-fine grained materials [J]. Scripta Materialia, 1996, 35(2): 143-146.

[3] GoforthR. E., HartwigK. T., CornwellL. R.LoweT. C., ValievR. Z.. Severe plastic deformation of materials by equal channel angular extrusion (ECAE) [C]. Investigations and Applications of Severe Plastic Deformation, 2000, Dordrecht, Kluwer Academic Publishers

[4] LeeJ. C., SeokH. K., SuhJ. Y.. Microstructural evolutions of the Al strip prepared by cold rolling and continuous equal channel angular pressing [J]. Acta Materialia, 2002, 50: 4005-4019

[5] TorizukaS., OhmoriA., Narayana MurtyS. V. S., NarayanaM., KotobuN.. Effect of strain on the microstructure and mechanical properties of multi-pass warm caliber rolled low carbon steel [J]. Scripta Materialia, 2006, 54: 563-568

[6] SatoY. S., UrataM., KokawaH., KeisukeI.. Hall-Petch relationship in friction stir welds of equal channel angular pressed aluminium alloys [J]. Materials Science and Engineering A, 2003, A354: 298-305

[7] DuZ.-z., HuangJ.-x., FuH.-g., WangJ.-t., ZhaoX.-cheng.. Microstructure and mechanical property of 65Mn steel after severe plastic deformation [J]. Journal of Jilin, 2006, University, Engineering and Technology: 143-147

[8] FurunoK., AkamatsuH., OhishiK., FurukawaM., HoritaZ., TerenceG. L.. Microstructural development in equal-channel angular pressing using a 60° die [J]. Acta Materialia, 2004, 52: 2497-2507

[9] HoritaZ., FujinamiT., NemotoM., LangdonT. G.. Improvement of mechanical properties for Al alloys using equal-channel angular pressing [J]. Journal of Materials Processing Technology, 2001, 117: 288-292

[10] DallaT. F., LapovokR., SandlinJ., ThomsonP. F., DaviesC. H. J., PerelomaE. V.. Microstructures and properties of copper processed by equal channel angular extrusion for 1–16 passes [J]. Acta Materialia, 2004, 52: 4819-4832

[11] KoY. G., ShinD. H., ParkK. T., ChongS. L.. An analysis of the strain hardening behavior of ultra-fine grain pure titanium [J]. Scripta Materialia, 2006, 54: 1785-1789

[12] MathisK., GubiczaJ., NamN. H.. Microstructure and mechanical behavior of AZ91 Mg alloy processed by equal channel angular pressing [J]. Journal of Alloys and Compounds, 2005, 394: 194-199

[13] WangX.-gang.Microstructures and mechanical properties of equal channel angular presses ultra-low carbon steel [D], 2004, Xi’an, Xi’an University of Architecture and Technology

[14] ShinD. H., SeoC. W., KimJ., KyungT. P., WungY. C.. Microstructures and mechanical properties of equal-channel angular pressed low carbon steel [J]. Scripta Materialia, 2000, 42: 695-699

[15] WangJ.-t., XuC., DuZ.-z., QuG.-z., TerenceG. L.. Microstructure and properties of a low-carbon steel processed by equal-channel angular pressing [J]. Materials Science and Engineering A, 2005, A410/411: 312-315

[16] XuS.-b., ZhaoG.-q., LuanY.-g., GuanY.-jin.. Numerical studies on processing routes and deformation mechanism of multi-pass equal channel angular pressing processes [J]. Journal of Materials Processing Technology, 2006, 176: 251-259

[17] WuY., BakerI.. An experimental study of equal channel angular extrusion [J]. Scripta Materialia, 1997, 37(4): 437-442