Structure of MgLiAl alloys after various routes of severe plastic deformation studied by TEM

Two MgLiAl alloys consisting either of a (hcp) + b (bcc) phases or only b phase were subjected to twist channel angular pressing TCAP (with helical component) or cyclic compression to a total strain of e = 5 in order to study the effectiveness of various deformation modes on grain refinement. After the first TCAP pass grains of a phase were refined from 30 lm down to about 6 lm and of b phase from initial 200 lm down to 8 lm. MAXStrain cycling led to much finer grains of a and b phases in the range 200 – 300 nm causing higher hardening and indicating higher effectiveness of the process. The Li ₂ MgAl precipitates were refined during severe plastic deformation (SPD) processes and in addition fine particles of hexagonal a phase of size below 100 nm were observed within the b phase showing orientation relationship (0001) a || (011) b. Two-phase material after SPD showed deviation of about 1.58 from the ideal Burgers orientation relationship (0001) a || (011) b.