Nanostructured laminar tungsten alloy with improved ductility by surface mechanical attrition treatment

Abstract

A nanostructured laminar W-La2O3 alloy (WL10) with improved ductility was prepared using a surface mechanical attrition treatment (SMAT). φ1.5 mm ZrO2 WL10 balls subjected to SMAT (called φ1.5 mm ZrO2 ball SMATed WL10) samples possess the best surface profile and excellent integrated mechanical properties (the ductile-brittle transition temperature (DBTT) value decreases by approximately 200 °C, and the bending strength decreases by 100 Mpa). A highly dense group of laminates was detected near the surface of the φ1.5 mm ZrO2 ball SMATed WL10 sample. The SMATed WL10 laminates were composed of a micro-grain layer, an ultrafine-grain layer and a nanosized-grain layer. The nanostructured laminar surface layer of the φ1.5 mm ZrO2 ball SMATed WL10 sample is approximately 1–2 μm. The top surface of the WL10 plates with and without the SMAT process possesses residual compressive stress of approximately −883 MPa and −241 MPa, respectively, in the y direction and −859 MPa and −854 MPa, respectively, in the x direction. The SMAT process could be a complementary method to further improve the toughness of tungsten-based materials.

Predicting surface deformation during mechanical attrition of metallic alloys

“…7 Predicted results using a full-coverage, multiple random impact model: a The global full coverage model for random multiple impacts during SMAT based on Eqs. (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24), each circle represents an indent induced by one impact; the indent sizes are different from each other due to the random oblique angles. b illustrates the local full-coverage finite element model.…”

“…(11,18) into Eq. (17), the relationship between the indent coverage and impact ball parameters can be obtained as:…”

“…Using this local fullcoverage, random multiple-impact model, the impact location and impact angle of each ball are obtained from the corresponding global coverage using Eqs. (17)(18)(19)(20)(21)(22)(23)(24). For such random, multiple impacts, we consider the overlap of indents by explicitly analyzing the first and second impacts.…”

“…[10][11][12][13] The technique was first introduced by Lu and Lu, 14 who exploited an ultrasonic set-up to vibrate spherical balls actuated by high-power ultrasound. 15 During this process, hard spherical balls are randomly impacted on surface of target materials, specifically to establish nano-sized crystalline layers on a variety of metallic materials, [16][17][18][19][20] including steels, nickel-based alloys and Mg-based alloys. 21 However, as numerous indents are generated on the sample surface layer by such impacts, the successful use of SMAT requires a number of parameters to be effectively controlled, including ball size, ball density, impact velocity and impact kinetic energy.…”

Manufacturing of tungsten and tungsten composites for fusion application via different routes

“…At present, the common deformation processing techniques of forging, rolling and swaging are exploited to improve the performances of W materials. W materials (such as pure W, W-K alloy, W-TiC, W-Y 2 O 3 and W-La 2 O 3 ) were processed by different deformation processing techniques with different processes to improve its microstructure and performances [37,63,[79][80][81][82][83][84][85][86][87]. Table 2 lists the relative density, grain size and some other performances of the obtained W materials after processed by different deformation processing techniques.…”