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Remanufacturing and Advanced Machining
The basic steps involved in superplastic forming of metal sheets include the stages
when a sheet is placed within a die cavity, then heated while high gas pressure is
evenly applied, causing plastic deformation of a metal at very large strains into a
complex-shaped, single-piece component (Mouritz, 2012), as illustrated in Figure 3.4.
As a rule, SPF involves slowly forming a sheet of material in a single-sided tool at a
temperature of about 500°C during a typical forming cycle, which for SPF is approximately 30 minutes or even longer (Powell et al., 2012).
Apart from sheet forming, SPF can be realized in other traditional metal forming
processes, such as rolling, drawing, and precise volumetric stamping. In particular,
SPF is advantageous in the following cases (Pupan and Kononenko, 2008):
1. Empty, complex shape and deep stretching can be obtained from a metal
sheet in one operation with superplastic deformation, while traditionally
several operations are required. Such components can be made of aluminum and titanium alloys, matrix metal composites, and even ceramic
materials.
2. Large and complex machine components, e.g., panels with wafer structure.
3. Tool forming, such as molds, punches, dies for stamping, etc. Some highspeed steels used for tools possess fine crystalline structures and require
little additional efforts to put them into the superplasticity state with optimal temperature and strain rate. On the other hand, carbon tool steels must
undergo initial thermal or thermomechanical treatment before making
them superplastic. The authors provide examples of reamers, cutters, and
countersinks made of R6M5 steel (Russian nomenclature, corresponding
to HS6-5-2 in Europe and T11302-М2 in the United States) in superplastic conditions of 810–820°С, strain rate 10 –1 s –1 , and specific deformation
pressure 180–250 MPa.
4. Ceramics and intermetallic compounds can be made superplastic due to
the specific preparation of a starting material and sintering conditions that
produce a fine-structured crystalline bulk material. As a result, ceramics
can be processed by forging or extrusion with elongation of 120–150%,
while in normal conditions they cannot stand elongation above 3%. Apart
from Al 2 O 3 , ZrO 2 , and their composites, a sort of bioactive ceramic
Ca 10 (PO 4 ) 6 (OH) 2 is found to exhibit superplasticity. This material, known
as calcium hydroxyapatite (HA), is one of the most important implantable
materials by analogy to mineral components of natural bones, used as a
substitute material for human hard tissues. Aluminides of titanium and
nickel are the most interesting intermetallic compounds.
Li et al. (2020) report unique superplasticity within a supercooled liquid region in
metallic glasses (MGs), making them ideal materials for precise and net-shaping
of various geometries by thermoplastic forming and breaking through limitations
of poor processability of bulk metallic glasses (BMGs) at ambient temperature.
BMGs are used for miniature fabrication in structural and functional applications,
so that superplasticity and small solidification shrinkage in the supercooled liquid
Remanufacturing and Advanced Machining
The basic steps involved in superplastic forming of metal sheets include the stages
when a sheet is placed within a die cavity, then heated while high gas pressure is
evenly applied, causing plastic deformation of a metal at very large strains into a
complex-shaped, single-piece component (Mouritz, 2012), as illustrated in Figure 3.4.
As a rule, SPF involves slowly forming a sheet of material in a single-sided tool at a
temperature of about 500°C during a typical forming cycle, which for SPF is approximately 30 minutes or even longer (Powell et al., 2012).
Apart from sheet forming, SPF can be realized in other traditional metal forming
processes, such as rolling, drawing, and precise volumetric stamping. In particular,
SPF is advantageous in the following cases (Pupan and Kononenko, 2008):
1. Empty, complex shape and deep stretching can be obtained from a metal
sheet in one operation with superplastic deformation, while traditionally
several operations are required. Such components can be made of aluminum and titanium alloys, matrix metal composites, and even ceramic
materials.
2. Large and complex machine components, e.g., panels with wafer structure.
3. Tool forming, such as molds, punches, dies for stamping, etc. Some highspeed steels used for tools possess fine crystalline structures and require
little additional efforts to put them into the superplasticity state with optimal temperature and strain rate. On the other hand, carbon tool steels must
undergo initial thermal or thermomechanical treatment before making
them superplastic. The authors provide examples of reamers, cutters, and
countersinks made of R6M5 steel (Russian nomenclature, corresponding
to HS6-5-2 in Europe and T11302-М2 in the United States) in superplastic conditions of 810–820°С, strain rate 10 –1 s –1 , and specific deformation
pressure 180–250 MPa.
4. Ceramics and intermetallic compounds can be made superplastic due to
the specific preparation of a starting material and sintering conditions that
produce a fine-structured crystalline bulk material. As a result, ceramics
can be processed by forging or extrusion with elongation of 120–150%,
while in normal conditions they cannot stand elongation above 3%. Apart
from Al 2 O 3 , ZrO 2 , and their composites, a sort of bioactive ceramic
Ca 10 (PO 4 ) 6 (OH) 2 is found to exhibit superplasticity. This material, known
as calcium hydroxyapatite (HA), is one of the most important implantable
materials by analogy to mineral components of natural bones, used as a
substitute material for human hard tissues. Aluminides of titanium and
nickel are the most interesting intermetallic compounds.
Li et al. (2020) report unique superplasticity within a supercooled liquid region in
metallic glasses (MGs), making them ideal materials for precise and net-shaping
of various geometries by thermoplastic forming and breaking through limitations
of poor processability of bulk metallic glasses (BMGs) at ambient temperature.
BMGs are used for miniature fabrication in structural and functional applications,
so that superplasticity and small solidification shrinkage in the supercooled liquid