26
S. Gupta
yield strength than Al-matrix. The authors proposed that the interaction between
microplasticity of Al-matrix and dislocation impediment by hard Ti 3 AlC 2 skeleton
was responsible for the observed behavior.
Different investigators have explored unique manufacturing processes to minimize
the reaction between metal and MAX phases. Agne and co-workers [48] reported
that V 2 AlC-Al composites can be successfully designed by water quenching from
temperatures >950 °C. Hu and co-workers [50] designed far from equilibrium interpenetrating Al-alloy-Ti 2 AlC composites by rapid infiltration (~30 s) which resulted
in Al alloy/Ti 2 AlC system with minimal reaction. In this study, the authors systematically controlled the microstructure by experimenting with 60 vol% and 73 vol%
Ti 2 AlC foams which were filtrated with Al-alloy. The pore size was also controlled
by using NaCl as pore formers. The authors were able to design 60 vol% Ti 2 AlC
foams with a pore size of 42–83 μm, 77–276 μm, and 167–545 μm, respectively.
The controlled pore size helped the authors to control the size of Al-alloy in these
foams.
Ti 2 AlC foams with ~40% porosity and finer pore size of 42–83 μm showed
the better compressive strength performance than foams with similar porosity but
greater pore size. In other words, composites with greater phase boundary area
which is directly correlated with size of Al-alloy were more successful in arresting
and deflecting cracks. Al-alloy (27 vol%)–Ti 2 AlC (73 vol%) showed an ultimate
compressive strength of 1095 MPa which was 10 times the yield strength of Al-alloy.
Comparatively, the ultimate compressive strength of Ti 2 AlC foam was 150 MPa.
Figure 4 plots the damping behavior different interpenetrating MAX-Metal
composites [52, 60]. For comparison, the data is also compared with porous Ti 3 SiC 2
and Ti 2 AlC [99, 100]. Amini and co-workers [51] reported Ti 2 AlC/Mg composites
which showed exceptional damping resistance. They manufactured these composites
by infiltrating Ti 2 AlC preforms (~50 vol% porous) with Mg at 750 °C for 1 h. They
reported that Mg had grain size of ∼35 ± 15 nm, and some solid solubility of Mg in
Ti 2 AlC to form (Ti 1-x Mg x ) 2 AlC (x ≤ 0.2). They classified these unique composites
as MAXMETs.
In a later study, Amini and Barsoum [52] used hot pressing (HPing) and melt infiltration (MI) to manufacture Ti 2 AlC/Mg composites. The HP samples were fabricated
by applying a stress of ~45 MPa at 500 °C. The hot-pressed samples with 40 and
50 vol% Mg were referred to as HP40 and HP50, respectively. The authors designed
50 vol% scaffolds for MI by, (a) cold-pressing and sintering (random orientation of
MAX phases), and (b) vibration-assisted manufacturing and sintering (samples were
oriented due to manual vibration). Mg chunks were then infiltrated by heating to
750 °C, hold for 30 min, and cool-down process. The oriented samples were then
machined parallel (sample code: MI-P) and normal (sample code: MI-N) to the basal
plane. The melt infiltrated samples oriented in random direction were referred to as
MI-R. Figure 4 shows the damping behavior of these composites. In their study, MI-P
composition showed the best damping behavior where MI-P had a W d (dissipated
energy normalized by cycle and volume) of ∼0.6 MJ/m
3 at 450 MPa. This study
also showed that the damping behavior of Mg-Ti 2 AlC composites is dependent of
the Ti 2 AlC particulates. The main role of the nanocrystalline Mg matrix was to,
S. Gupta
yield strength than Al-matrix. The authors proposed that the interaction between
microplasticity of Al-matrix and dislocation impediment by hard Ti 3 AlC 2 skeleton
was responsible for the observed behavior.
Different investigators have explored unique manufacturing processes to minimize
the reaction between metal and MAX phases. Agne and co-workers [48] reported
that V 2 AlC-Al composites can be successfully designed by water quenching from
temperatures >950 °C. Hu and co-workers [50] designed far from equilibrium interpenetrating Al-alloy-Ti 2 AlC composites by rapid infiltration (~30 s) which resulted
in Al alloy/Ti 2 AlC system with minimal reaction. In this study, the authors systematically controlled the microstructure by experimenting with 60 vol% and 73 vol%
Ti 2 AlC foams which were filtrated with Al-alloy. The pore size was also controlled
by using NaCl as pore formers. The authors were able to design 60 vol% Ti 2 AlC
foams with a pore size of 42–83 μm, 77–276 μm, and 167–545 μm, respectively.
The controlled pore size helped the authors to control the size of Al-alloy in these
foams.
Ti 2 AlC foams with ~40% porosity and finer pore size of 42–83 μm showed
the better compressive strength performance than foams with similar porosity but
greater pore size. In other words, composites with greater phase boundary area
which is directly correlated with size of Al-alloy were more successful in arresting
and deflecting cracks. Al-alloy (27 vol%)–Ti 2 AlC (73 vol%) showed an ultimate
compressive strength of 1095 MPa which was 10 times the yield strength of Al-alloy.
Comparatively, the ultimate compressive strength of Ti 2 AlC foam was 150 MPa.
Figure 4 plots the damping behavior different interpenetrating MAX-Metal
composites [52, 60]. For comparison, the data is also compared with porous Ti 3 SiC 2
and Ti 2 AlC [99, 100]. Amini and co-workers [51] reported Ti 2 AlC/Mg composites
which showed exceptional damping resistance. They manufactured these composites
by infiltrating Ti 2 AlC preforms (~50 vol% porous) with Mg at 750 °C for 1 h. They
reported that Mg had grain size of ∼35 ± 15 nm, and some solid solubility of Mg in
Ti 2 AlC to form (Ti 1-x Mg x ) 2 AlC (x ≤ 0.2). They classified these unique composites
as MAXMETs.
In a later study, Amini and Barsoum [52] used hot pressing (HPing) and melt infiltration (MI) to manufacture Ti 2 AlC/Mg composites. The HP samples were fabricated
by applying a stress of ~45 MPa at 500 °C. The hot-pressed samples with 40 and
50 vol% Mg were referred to as HP40 and HP50, respectively. The authors designed
50 vol% scaffolds for MI by, (a) cold-pressing and sintering (random orientation of
MAX phases), and (b) vibration-assisted manufacturing and sintering (samples were
oriented due to manual vibration). Mg chunks were then infiltrated by heating to
750 °C, hold for 30 min, and cool-down process. The oriented samples were then
machined parallel (sample code: MI-P) and normal (sample code: MI-N) to the basal
plane. The melt infiltrated samples oriented in random direction were referred to as
MI-R. Figure 4 shows the damping behavior of these composites. In their study, MI-P
composition showed the best damping behavior where MI-P had a W d (dissipated
energy normalized by cycle and volume) of ∼0.6 MJ/m
3 at 450 MPa. This study
also showed that the damping behavior of Mg-Ti 2 AlC composites is dependent of
the Ti 2 AlC particulates. The main role of the nanocrystalline Mg matrix was to,