A calcium-bearing magnesium and rare earth element alloy consists essentially of, in mass percent, zinc (Zn): 1-3%; aluminum (Al): 1-3%; calcium (Ca): 0.1-0.4%; gadolinium (Gd): 0.1-0.4%; yttrium (Y): 0-0.4%; manganese (Mn): 0-0.2%; and balance magnesium (Mg).

A calcium-bearing magnesium and rare earth element alloy consists essentially of, in mass percent, zinc (Zn): 1-3%; aluminum (Al): 1-3%; calcium (Ca): 0.1-0.4%; gadolinium (Gd): 0.1-0.4%; yttrium (Y): 0-0.4%; manganese (Mn): 0-0.2%; and balance magnesium (Mg).

Provided is a multilayer zinc alloy plated steel material comprising a base steel material and multiple plating layers formed on the base steel material, wherein each of the multiple plating layers includes one of a Zn plating layer, a Mg plating layer, and a Zn—Mg alloy plating layer, and the ratio of the weight of Mg contained in the multiple plating layers to the total weight of the multiple plating layers is from 0.13 to 0.24.

Provided is a multilayer zinc alloy plated steel material comprising a base steel material and multiple plating layers formed on the base steel material, wherein each of the multiple plating layers includes one of a Zn plating layer, a Mg plating layer, and a Zn—Mg alloy plating layer, and the ratio of the weight of Mg contained in the multiple plating layers to the total weight of the multiple plating layers is from 0.13 to 0.24.

An exemplary embodiment of the present invention relates to a magnesium alloy sheet and a manufacturing method thereof. The exemplary embodiment of the present invention provides a magnesium alloy sheet including 0.5 to 2.1 wt % of Al, 0.5 to 1.5 wt % of Zn, 0.1 to 1.0 wt % of Ca, and a balance of Mg and inevitable impurities, with respect to a total of 100 wt % of the magnesium alloy sheet.

To provide a magnesium alloy with improved corrosion resistance by surface modification, and a production method thereof. (1) The surface-modified magnesium alloy comprising: a magnesium alloy having an arbitrary shape; a magnesium fluoride layer formed by fluorination of the surface of the magnesium alloy; and a diamond-like carbon layer formed on the magnesium fluoride layer. (2) The method comprising: subjecting a surface of a magnesium alloy having an arbitrary shape to fluorination treatment to form a magnesium fluoride layer on the surface of the magnesium alloy, and then subjecting the magnesium alloy with the magnesium fluoride layer to be placed in a high-frequency plasma CVD device such that a source gas containing carbon is introduced to form a diamond-like carbon layer on the magnesium fluoride layer.

To provide a magnesium alloy with improved corrosion resistance by surface modification, and a production method thereof. (1) The surface-modified magnesium alloy comprising: a magnesium alloy having an arbitrary shape; a magnesium fluoride layer formed by fluorination of the surface of the magnesium alloy; and a diamond-like carbon layer formed on the magnesium fluoride layer. (2) The method comprising: subjecting a surface of a magnesium alloy having an arbitrary shape to fluorination treatment to form a magnesium fluoride layer on the surface of the magnesium alloy, and then subjecting the magnesium alloy with the magnesium fluoride layer to be placed in a high-frequency plasma CVD device such that a source gas containing carbon is introduced to form a diamond-like carbon layer on the magnesium fluoride layer.

A downhole tool comprising magnesium is placed in a well bore in a subterranean formation for performance of a downhole operation. After performance of the downhole operation, rather than mechanically retrieving or removing the tool, at least a portion of the magnesium in the downhole tool is dissolved by contacting the downhole tool with an aqueous ammonium chloride solution.

A downhole tool comprising magnesium is placed in a well bore in a subterranean formation for performance of a downhole operation. After performance of the downhole operation, rather than mechanically retrieving or removing the tool, at least a portion of the magnesium in the downhole tool is dissolved by contacting the downhole tool with an aqueous ammonium chloride solution.

According to an exemplary embodiment of the present invention, a manufacturing method of a magnesium alloy plate includes: (a) solution-treating a magnesium casting material containing 0.5 to 10 wt % of zinc (Zn), 1 to 15 wt % of aluminum (Al), and a balance of magnesium (Mg) and inevitable impurities at 300 to 500° C. for 1 to 48 hours; (b) pre-heating the solution-treated magnesium casting material at 300 to 500° C.; and (c) of rolling the pre-heated magnesium casting material together with a constraint member selected by following Relational Expression 1 to satisfy Relational Expressions 2 and 3; and (d) solution-treating a thus-rolled magnesium alloy plate at 300 to 500° C. for 0.5 to 5 hours. Relational Expressions 1 to 3 are as described in the specification.