The Study On Compressive Creep Properties Of The Ultra-Light Mg-Li Based Alloy

Mg-Li alloy was called Ultra-Light Mg based alloy with density between 1.35g/m~3 and 1.65g/m~3, and it is the lightest and innocuity metal structural materials. It has high Specific strength and stiffness, good shock absorption property, and electromagnetic shielding, can antis penetrate of high-energy particles. It will reduce the consumption of energy if these alloys are successfully widespread applied.In this paper, the development and research on Mg-Li based alloy are systematically presented, and then the compressive creep behavior of two kind of Mg-Li-Al alloy, LA141 single phase β, and LAZ933 two phase α + β , are investigated at different temperature and compressive stress with special apparatus. OM and SEM, XRD test techniques are adapted to analysis the changes occurred in compressive creep such as phase transformation, microstructure evolution, and the mechanisms of compressive creep were discussed.In the test condition, temperature in the range of 30~85℃ and different compressive stress from 37.3MPa to 74.66MPa, the result indicate:(1) Compressive creep deformations of two alloys LA141 and LAZ933, creep increases with the increasing of temperature and compressive stress. There is linear logarithmic relationship between the steady creep rate and all the temperature and stress used. The steady creep rate obeys an empirical equation ε_s = Aσ~n exp[-Q_c/(RT)]. And the steady compressive creep rate of LA141 alloy was lower than that of LAZ933 alloy.(2) For LA141, the stress exponents (n) are similar at different temperatures and the appearance activation energies (￡)?) are not greatly different under different stresses, the average values are 3.16 and 104.\KJImol respectively. The rate of steady creep is controlled by self-diffusion of Li and by a dislocation glide. During creep test phase transformation had occurred as:/3-*0'(MgLi2Al) + a(3) For LAZ933, the stress exponents are very high (n>6) and the apparent creep activation energies increase gradual (39.6—76.1 KJ/moJ). Creep mechanism then change from grain-boundary sliding and dislocation glide to second-phase particles strengthen and diffuse mechanism.Under low compress stress 37.3MPa, the mainly creep mode is grain-boundary sliding. As compress stress increased to 50.0MPa, then dislocation glide joins in the creep mode.When compress stress increased to 62.2 and 74.6MPa, the creep mechanism had changed to second-phase particle strengthen and diffuse mechanism. Under compress stress of 74.6MPa the apparent creep activation energy is 16.\KJ/mol. During creep test phase transformation had occurred as:LiMg2Zn3 -> LiMgZnAlnMn4 -* Al3Mg2 + Al2Mg + (j3- Mn)...