Aluminum alloy heat exchanger

An aluminum alloy heat exchanger produced by excluding flux, the heat exchanger comprising:

• a flow channel forming member to form a flow channel in which a fluid flows through;
• a heat transfer member having a heat transfer surface, the heat transfer member joined to a flow channel forming surface of the flow channel forming member, the heat transfer surface wider than the flow channel forming surface;
• a reinforcing member joined to the flow channel forming member to reinforce the flow channel forming member;
• a joining member joined to the reinforcing member;
• a first fillet formed in a first braze joining portion in which the heat transfer member and the flow channel forming member join with each other;
• a second fillet formed in a second braze joining portion in which the flow channel forming member and the reinforcing member join with each other;
• and
• a third fillet formed in a third braze joining portion in which the reinforcing member and the joining member join with each other,
• wherein the flow channel forming member, the heat transfer member, the reinforcing member and the joining member are composed of aluminum alloys, respectively,
• wherein an average plate thickness of the flow channel forming member is in the range of 0.200 mm or more and 0.600 mm or less, an average plate thickness of the heat transfer member is in the range of 0.025 mm or more and 0.150 mm or less, an average plate thickness of the reinforcing member is in the range of 0.600 mm or more and 2.000 mm or less, and an average plate thickness of the joining member is in the range of 0.600 mm or more and 2.000 mm or less,
• wherein each of the first to third fillets is composed of an aluminum alloy containing magnesium, bismuth, and silicon,
• wherein a concentration of the magnesium of each of the first to third fillets is in the range of 0.2% or more and 2.0% or less by mass,
• wherein at least one of the flow channel forming member and the heat transfer member includes a brazing material layer on a surface thereof,
• wherein when the flow channel forming member includes the brazing material layer, a concentration of magnesium of the flow channel forming member at its plate thickness center is in the range of 0.1% or more and 1.0% or less by mass, and when the heat transfer member includes the brazing material layer, a concentration of magnesium of the heat transfer member at its plate thickness center is in the range of 0.2% or more and 1.0% or less by mass.