JPS59140346A - Aluminum alloy with high toughness - Google Patents

Abstract

PURPOSE:To improve remarkably the toughness of an Al-Zn-Mg alloy for a structural material by adding plural elements for improving toughness to the Al alloy and by reducing the amounts of Fe and Si in the alloy. CONSTITUTION:The composition of an Al-Zn-Mg alloy with medium tensile strength and yield strength is composed of 5.5-6.5% Zn, 0.8-1.2% Mg, 0.05- 0.20% Zr, 0.05-0.15% Co, 0.05-0.15% Ti, <0.12% Fe, <0.10% Si and the balance Al. Zr, Co and Ti are added as elements for improving toughness, and the amounts of Fe and Si deteriorating toughness are reduced, so the toughness of the Al alloy is remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy with high toughness, and more specifically, to a medium-strength Aj! for structural materials. -Z It relates to improving the toughness of n-Mg alloy.

In recent years, with the expansion of the uses of aluminum alloys, the amount of medium-strength alloys used for structural materials as various strength members has increased, and AA! =Mg-8t alloy includes JIS 6061 alloy, and AA'-Zn-Mg alloy includes JIS7NO1 alloy. However, in terms of strength, these alloys can obtain sufficient strength as medium-strength alloys by subjecting them to the T5 or T6 treatment specified by JIS, but they have the disadvantage that they do not have sufficient toughness.
Therefore, there has been a demand for the development of medium-strength alloys with excellent toughness.

The present invention aims to solve the above problems, and the aluminum alloy of the present invention has Zn5.5 to 6
．． 5% by weight, Mg 0.8-1.2% by weight, Zr 0-
05-0.20% by weight, Co 0-05-0.15% by weight, TiO, 05-0.15% by weight, Fe0.12
% by weight or less, SiO, 10% by weight or less, the balance is AI! The alloy of the present invention has medium tensile strength and yield strength, and excellent toughness.

The reason for limiting the composition of each component in the alloy of the present invention is as follows.

ZnN Mg is the main additive element forming MgZn2, and sufficient strength cannot be obtained unless Zn reaches 5.5% by weight and Mg reaches 8% by weight, and when Zn reaches 6.5% by weight and Mg
When g exceeds 1.2% by weight, stress corrosion cracking tends to occur and workability decreases.

Zr, Co, and T1 are Zr-based, Co-based,
It precipitates as a Tl-based compound and is effective in improving the toughness of the alloy, but the effect cannot be expected if it is added alone□
Zr and Ti are also effective in preventing stress corrosion cracking. Z
r is sail 05% by weight, Co is 0.05% by weight, Ti is 0%
．． If the amount is less than 0.5% by weight, the improvement in toughness is insufficient.
, Zr 0.20% by weight, Co 0.15% by weight, Ti
If it exceeds 0.15% by weight, macrocompounds are formed, resulting in a decrease in toughness and workability.

The alloy of the present invention inevitably contains impurities from raw materials, but in order to obtain a medium-strength alloy with excellent toughness, keep Fe at 0.12% by weight or less and Si at 0.10% by weight or less. There is a need to. If Fe exceeds 0.12% by weight, toughness decreases, and if Si exceeds 0.10% by weight, strength decreases.

Next, examples of the present invention will be shown. Table 1 shows the alloy component composition of one embodiment of the present invention. Mold ingots with these compositions (
50ram x 40tan x 200ttrm
) was prepared by a conventional method and homogenized at 460° C. for 6 hours, and then a round bar (29 mm+!1×90 m+) was cut out, and an extruded material with a cross section of 23×211111 was made using a test extruder. This extruded material was used for tensile testing.
S 13 No. B test piece was used for 90° bending test.
A test piece of tran x 2 m x 60 m was prepared and subjected to solution treatment at 470°C for 30 minutes. after that,
Cooling rate 1.8°C/se for T4 and T5 processing
The mixture was cooled to room temperature at e. Also, for T6 treatment, it was water-cooled. In the T4 treatment, room temperature aging was performed for 10 days after cooling to room temperature, and in the T5 and T6 treatments, tempering treatment was performed at 120° C. for 24 hours.

Table 82 shows the mechanical properties at room temperature of the test pieces subjected to the above aging. That is, the alloy of the present invention has a tensile strength of 32
~39VTMn! , the yield strength is 19 to 31 Kg/cm", and the bendability R/l, which is an index of toughness, is R
/l = 0.25, no cracking occurs and excellent toughness As stated above, the alloy of the present invention maintains medium strength in terms of tensile strength and proof stress, and also has low toughness. It has outstanding properties and can be used for various purposes as a medium-strength alloy for structural materials.

Claims (1)

[Claims] Zn5.5-6.5% by weight, Mg 0.8-1.2% by weight, zrO005-0.20% by weight, Co O-0
5-0.15% by weight, TiO, 05-0.15% by weight
, F e O-12% by weight or less, Sl o, io heavy weight multi-column lower balance is A! Aluminum alloy with high toughness and strong strength even when exposed to unavoidable impurities.