Table 4.

Effect of alloying elements and processing parameters on the different properties of Zn alloys after thermomechanical processing.

Thermomechanical processing	Composition (wt.%)	Processing parameters	Key microstructures, mechanical and corrosion properties	Ref.
HE (Hot extrusion)	Zn-xAg (x = 0, 2.5, 5.0, 7.0)	Melting at650 °C + homogenization at 410 °C for 12 h + HE at 250 °C with an extrusion ratio (ER) of 14: 1. Air cooling to room temperature (RT).	HE produced significant grain refinement (GR) of Zn–Ag alloys. The grain size (GS) decreased with increasing Ag content, with a remarkably fine and equiaxed microstructure and a mean grain size of about 1.5 μm for Zn-7.0Ag. Also, increasing Ag content monotonically improved σUTS from 203 to 287 MPa due to GR and a higher volume fraction (VF) of fine AgZn3 particles. The alloys showed slightly faster CRs compared to pure Zn.	[102]
	Zn-xCu (x = 1, 2, 3, and 4)	Melting at 650 °C + homogenization at 360 °C for 8 h followed by water quenching (WQ) + HE at 280 °C with an ER of 9: 1. Air cooling to RT.	The σTYS, σUTS and ε of Zn-xCu alloys increased dramatically with increasing Cu content. Notably, the ε of Zn–4Cu reached 50.6%, which is beneficial for processing of micro-tubes for stent fabrication. The CRs of the alloys in SBF was low, varies from 22.1 to 33.0 μm/y.	[162]
	Zn–3Cu-xMg (x = 0, 0.1, 0.5 and 1.0)	Melting at 650–680 °C + homogenization at 360 °C for 8 h followed by WQ + then HE at 280 °C with an ER of 9: 1, Air cooling to RT.	The VF of Mg2Zn11 phase increased gradually with increasing Mg concentration. σTYS was improved from 213.7 to 426.7 MPa, while ε decreased from 47.1 to 0.9%. The CR increased from 11.4 to 43.2 μm/y.	[163]
	Pure Zn, Zn-0.8 Mg, Zn-1.6 Mg	Melting at 550–600 °C under air atmosphere + homogenization at 525 °C for 8 h followed by air cooling to RT + HE at 300 °C with an ER of 10: 1. Air cooling to RT.	The Zn–Mg alloys contained recrystallized Zn grains of 12 μm in size, and fine Mg2Zn11 particles arranged parallel to the extrusion direction. σCYS, σTYS, σUTS and H increased with increasing Mg content. Zn-0.8 Mg showed the best combination of mechanical properties (σTYS = 203 MPa, σUTS = 301 MPa and ε = 15%).	[164]
	Pure Zn, Zn-0.02Mg-0.02Cu	Melting at suitable temperature with Ar gas protection + HE at 180 °C with an ER of 16: 1. Air cooling to RT.	Compared with pure Zn, the Zn alloy showed higher mechanical properties (σTYS = 216 MPa, σUTS = 262 MPa, and H = 74 Hv).	[165]
	Pure Zn, Zn–1Mg-xZr (x = 0.1, 0.25, 0.4)	Melting at suitable temperature with Ar gas protection + homogenization at 343 °C for 36 h followed by WQ + HE at 250 °C with an ER of 16.7: 1. Air cooling to RT.	The HE seriously deformed the primary Zn-rich crystals and broke the Mg2Zn11 and Zn22Zr intermetallic compounds into small particles. Adding Mg and Zr to pure Zn significantly improved H (37–95 Hv), σTYS (61–248 MPa), σUTS (98–316 MPa) and σCYS (131–301 MPa). The addition of Zr to binary Zn–1Mg alloy slightly improved H, σUTS, σTYS and σTYS, and significantly improved ε from 0.8% to 4.7%.	[166]
HR (Hot Rolling)	Pure Zn, Zn–1Mg, Zn–1Ca, Zn–1Sr	Melting at 630 °C in mixed gas atmosphere (SF6 + CO2) for 0.5 h followed by air cooling to RT + rolling at 250 °C with total 81% reduction in thickness.	Hot rolling significantly increased the σTYS, σUTS and ε of as-cast pure Zn, Zn–1Mg, Zn–1Ca and Zn–1Sr alloys from 10 to 30 MPa, 18–50 MPa and 0.3–5.8%; 130–192 MPa, 180–237 MPa and 2–9%; 119–206 MPa, 165–252 MPa and 2.1–12.7%, and 120–188 MPa, 171–229 MPa and 2–20%, respectively. However, H values remained almost steady for pure Zn and alloys except Zn–1Ca alloy. The sequence of CR is Zn < Zn–1Mg < Zn–1Ca < Zn–1Sr.	[147]
	Zn–4Ag	Melting at 750 °C with Ar gas protection + homogenization at 300 °C for 1 h followed by furnace cooling to RT + HR at 200 °C with total 70% reduction in diameter + annealed at 390 °C for 15 min + precipitation hardened in an oil bath for 10 min at 100 °C.	After thermomechanical treatment, σTYS, σUTS and ε of the alloy are 157 MPa, 261 MPa, and 37%, respectively, rendering this alloy a promising material for bioresorbable stents.	[167]
	Pure Zn, Zn-5Ge	Melting at 500 °C with Ar gas protection + homogenization at 340 °C for 10 h followed by air cooling to RT + HR at 200 °C with total 80% reduction in thickness.	After hot rolling, the grains of the Zn–5Ge alloy were elongated along the deformation direction and the eutectic Ge phase was significantly refined. Hot rolling significantly increased the σTYS, σUTS, ε and CR of Zn-5Ge alloys from 48 to 175 MPa, 54–237 MPa, 1.1–22% and 0.127–0.225 mm/y, respectively, while the H values decreased from 68 to 60 Hv.	[168]
	Zn–1Cu-0.1Ti	Melting at 550–600 °C with Ar gas protection + homogenization at 340 °C for 10 h followed by air cooling to RT + rolling (HR) at 250 °C with total 80% reduction in thickness + cold rolling to a 40% total reduction in thickness.	HR and HR + CR Zn–1Cu-0.1Ti contained a η-Zn phase, a ε-CuZn5 phase, and an intermetallic phase of TiZn16. The HR + CR alloy exhibited a σTYS of 204 MPa, a σUTS of 250 MPa, and a ε of 75%; significantly higher than those of HR alloy. The CR in Hanks' solution was 0.032 mm/y for HR + CR alloy and 0.034 mm/y for HR alloy. The HR alloy showed the best wear resistance.	[152]
	Zn-0.8Mn-0.4Ca	Melting at 725 °C with Ar gas protection + homogenization at 360 °C for 6 h followed by water quenched + HR at 100 °C with total 64% reduction in thickness.	Hot rolling significantly refined Zn grains of Zn–Mn–Ca alloy from 289 to 5 μm and increased the σTYS, σUTS and ε from 112 to 245 MPa, 120–323 MPa and 0.3–12%, respectively.	[169]
ECAP (equal channel angular pressing)	Pure Zn	Melting at 650 °C for 1 h + Annealing at 450 °C for 4 h + ECAP processing = 22 °C with extrusion rate (ER) of 0.1 mm/s + angle between channels (ϕ) = 90°	The ECAP caused GR of pure Zn with a mean GS decreased from 509 to 20 μm, leading to an increase in ε by ~ 45% and a decrease in σUTS from 97 to 91 MPa.	[170]
	Zn-0.8Ag	Melting at 650 °C for 1 h + Annealing at 450 °C for 4 h + ECAP processing = 22 °C with ER of 0.1 mm/s + ϕ = 90°	The alloy contained recrystallized, equiaxed grains with an average GS of ~2.7 μm, 2.6 μm, and 2.2 μ, displaying a ε of 390%, 448%, and 428% in X, Y, and Z directions, respectively.	[171]
	Zn-0.82Ag	Melting at 650 °C for 1 h + Annealing at 450 °C for 4 h + ECAP processing = 22 °C with ER of 0.1 mm/s + ϕ = 90°	ECAP caused grain refining to 3.2 μm and enhanced ε up to 245%. The GR increased grain boundary sliding, viscous glide, and diffusion creep that could be responsible for substantial ductility.	[170]
	Zn-0.3Al	Melting at 470 °C for 1 h + Homogenization at 320 °C for 12 h + Hot rolled = At 100 °C with a 35% reduction in thickness + ECAP processing = 22 °C with ER of 0.1 mm/s + ϕ = 90°	Multi-pass ECAP refined the coarse-grained (100–250 μm) microstructure into fine grains (~2 μm) and increased ε substantially (maximum 1000%).	[172]
	Zn-0.49Cu	Melting at 650 °C for 1 h + Annealing at 450 °C for 4 h + ECAP processing = 22 °C with ER of 0.1 mm/s + ϕ = 90°	ECAP resulted GR and increased ε by over 500%, but reduced σTYS and σUTS twice compared to the same alloys processed by HE. The GR concurrently raised the activity of grain boundary sliding, viscous glide and diffusion creep, leading to significant enhancement of ductility.	[170]
	Zn-0.5Cu	Melting at 650 °C for 1 h + Annealing at 450 °C for 4 h + ECAP processing = 22 °C with ER of 0.1 mm/s + ϕ = 90°	GR occurred due to four-pass ECAP with an average GS from 560 to 1 μm, leading to an increase in ε by 510%.	[173]
	Zn–3Mg	Melting at 550 °C for 1 h + homogenized at 370 °C for 15 h followed by WQ + ECAP processing = 22 °C with ER of 1 mm/s + ϕ = 120°	Two-pass ECAP led to GR decreased from 48 to 1.8 μm, which notable improved the σUTS and ε from 84 to 220 MPa and 1.3–6.3%, respectively, in addition to a decrease in CR from 0.30 to 0.24 mm/y.	[160]
	Zn-0.42Mn	Melting at 650 °C for 1 h + Annealing at 450 °C for 4 h + ECAP processing = 22 °C with ER of 0.1 mm/s + angle between channels = 90°	ECAP caused GR with mean GS decreased from 7.0 to 1.1 μm, resulting in an increase in ε by 108%, but a decrease in σTYS from 187 to 148 MPa and σUTS from 251 to 188 MPa, respectively.	[170]
HPT (high-pressure torsion)	Pure Zn	Pressure, P = 1 GPa, Rotation speed = 1 rpm, Number of turns, N = 0, 1, 3, 5.	Average GS increased from 59 to 80 μm and σTYS increased from 61 to 114 MPa with increasing N.	[156]
	Zn–Mg hybrids	Pressure, P = 6 GPa, Rotation speed = 1 rpm, Number of turns, N = 1, 5, 15, 30.	Homogenous microstructure obtained at 15 turns. GS decreased from 43 to 10 μm and H increased from 40 to 250 H V with increasing N from 1 to 30.	[174]
	Zn-0.5Cu	Pressure, P = 6 GPa, Rotation speed = 1 rpm, Number of turns, N = 0, ½, 1, 2, 5, 10.	HPT caused GR and texture sharpening, leading to an increase in ε by 285%. The σTYS and σUTS also increased with increasing N.	[175]