Atomistic study of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>{</mml:mo> <mml:mrow> <mml:mn>10</mml:mn> <mml:mover accent="true"> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>2</mml:mn> </mml:mrow> <mml

Molecular dynamics techniques are used to investigate <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mo>{</a:mo> <a:mrow> <a:mn>10</a:mn> <a:mover accent="true"> <a:mn>1</a:mn> <a:mo>¯</a:mo> </a:mover> <a:mn>2</a:mn> </a:mrow> <a:mo>}</a:mo> </a:mrow> </a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mo>{</c:mo> <c:mrow> <c:mn>11</c:mn> <c:mover accent="true"> <c:mn>2</c:mn> <c:mo>¯</c:mo> </c:mover> <c:mn>1</c:mn> </c:mrow> <c:mo>}</c:mo> </c:mrow> </c:math> twin thickening processes through spontaneous formation of twinning disconnections (TD) under applied shear deformation with a constant strain rate, based on an embedded atom method potential model of Zr. The observed stress responses and twin boundary structure changes verify that both twins thicken through TD formation. However, the thickening processes of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:mo>{</e:mo> <e:mrow> <e:mn>10</e:mn> <e:mover accent="true"> <e:mn>1</e:mn> <e:mo>¯</e:mo> </e:mover> <e:mn>2</e:mn> </e:mrow> <e:mo>}</e:mo> </e:mrow> </e:math> and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mrow> <g:mo>{</g:mo> <g:mrow> <g:mn>11</g:mn> <g:mover accent="true"> <g:mn>2</g:mn> <g:mo>¯</g:mo> </g:mover> <g:mn>1</g:mn> </g:mrow> <g:mo>}</g:mo> </g:mrow> </g:math> twins show significant differences. While <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mrow> <i:mo>{</i:mo> <i:mrow> <i:mn>10</i:mn> <i:mover accent="true"> <i:mn>1</i:mn> <i:mo>¯</i:mo> </i:mover> <i:mn>2</i:mn> </i:mrow> <i:mo>}</i:mo> </i:mrow> </i:math> TD loops were observed to form and expand during the twin thickening process, the <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:mrow> <k:mo>{</k:mo> <k:mrow> <k:mn>11</k:mn> <k:mover accent="true"> <k:mn>2</k:mn> <k:mo>¯</k:mo> </k:mover> <k:mn>1</k:mn> </k:mrow> <k:mo>}</k:mo> </k:mrow> </k:math> twin boundary exhibits a more structurally disordered interface throughout the simulation, and no sharp boundary corresponding to a <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:mo>{</m:mo> <m:mrow> <m:mn>11</m:mn> <m:mover accent="true"> <m:mn>2</m:mn> <m:mo>¯</m:mo> </m:mover> <m:mn>1</m:mn> </m:mrow> <m:mo>}</m:mo> </m:mrow> </m:math> TD ‘loop’ can be identified. Moreover, the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"> <o:mrow> <o:mo>{</o:mo> <o:mrow> <o:mn>11</o:mn> <o:mover accent="true"> <o:mn>2</o:mn> <o:mo>¯</o:mo> </o:mover> <o:mn>1</o:mn> </o:mrow> <o:mo>}</o:mo> </o:mrow> </o:math> twin requires a much lower critical shear stress for twin thickening, approximately 10% of that for the <q:math xmlns:q="http://www.w3.org/1998/Math/MathML"> <q:mrow> <q:mo>{</q:mo> <q:mrow> <q:mn>10</q:mn> <q:mover accent="true"> <q:mn>1</q:mn> <q:mo>¯</q:mo> </q:mover> <q:mn>2</q:mn> </q:mrow> <q:mo>}</q:mo> </q:mrow> </q:math> twin. The low critical shear stress of <s:math xmlns:s="http://www.w3.org/1998/Math/MathML"> <s:mrow> <s:mo>{</s:mo> <s:mrow> <s:mn>11</s:mn> <s:mover accent="true"> <s:mn>2</s:mn> <s:mo>¯</s:mo> </s:mover> <s:mn>1</s:mn> </s:mrow> <s:mo>}</s:mo> </s:mrow> </s:math> twin thickening also indicates that these twins should grow easily once nucleated. To the extent that these results apply to hexagonal-close-packed (HCP) materials more generally, promotion of <u:math xmlns:u="http://www.w3.org/1998/Math/MathML"> <u:mrow> <u:mo>{</u:mo> <u:mrow> <u:mn>11</u:mn> <u:mover accent="true"> <u:mn>2</u:mn> <u:mo>¯</u:mo> </u:mover> <u:mn>1</u:mn> </u:mrow> <u:mo>}</u:mo> </u:mrow> </u:math> twin nucleation may be an effective way to enhance twinning deformation and twin boundary-related work hardening in HCP materials, with the potential to manipulate the balance between strength and ductility.